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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: nat on April 06, 2008, 08:11:01 AM
Title: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on April 06, 2008, 08:11:01 AM
It's long been known that by replacing all the capacitors in the audio circuit on the Express PCB you are able to cure all sound issues, but video issues have been a bit of a grey area. What has been unknown (until now) is just which component is directly linked to the common video problem these units are beginning to have. Let's give a round of applause to Sinistron, the real hero in all this, for donating a TurboExpress with bad video for me to butcher on the operating table. It was a very long and tedious process, as I ended up replacing almost everything on the board by the time I was done and I had to play test after every component which meant quite a bit of assembly and disassembly. The culprit turned out to be the smallest, most innocuous capacitor on the entire board and the only reason it wasn't the very last one I did was because there was one cap I didn't have a proper uF/voltage match for. At the very least all this paid off and finally put to rest just what causes the no video issue. Real quick: the capacitor in question is in the power circuit, specifically, the line that supplies the mains to the LCD. This cap fails, dries out, bleeds, etc causing insufficient voltage supplied to run the LCD.
So let's get down to it.... I took photos documenting the entire process, but I'll only post the relevant ones here.
(http://pic.photobucket.com/bwe.png) Circled in green is the audio circuit. We already know what these caps are for, so we ignored them for this procedure. Circled in red is the culprit for the video issue. You can barely see it, can't you?
(http://pic.photobucket.com/bwe.png) Since I didn't know where the problem was specifically, I removed the shield covering the CPU, VDC, etc. The caps circled in blue are the ones that are exposed by removing the shield. It is not necessary to replace these to fix the video, but Sinistron got a freebie on this one. I included this pic so folks who might want to replace EVERYTHING can see just what's under the shield.
(http://pic.photobucket.com/bwe.png) Circled in red is the replacement cap I installed in place of the bad on. The cap is a 4.7uF 35-volt electrolytic. This is THE culprit of the backlight-but-no-picture video issue. Replace it and your video works again.
(http://pic.photobucket.com/bwe.png) Just a final look at the board after I was done with it. I had to run wires to remote-mount a few of the replacement caps due to not enough room on the board, etc. FYI, there is plenty of open space down behind where the batteries sit where you can remote-mount caps if you need to.
There you have it. It's a simple fix, really, and luckily it's probably the most easily accessible cap on the entire board.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Sinistron on April 06, 2008, 08:23:40 AM
:clap:
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 06, 2008, 08:30:31 AM
That's a hell of a lot easier than fixing the audio capacitor!
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nectarsis on April 06, 2008, 08:31:11 AM
Nat saves the day again :)
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: ceti alpha on April 06, 2008, 11:37:15 AM
That's awesome nat!!! Sin's a happy camper and you saved a TE from going to the garbage dump. :clap: :dance:
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: esteban on April 06, 2008, 12:51:45 PM
When my TE's fail, I will not be as depressed as I would have been, say, yesterday.
nat, you rock!
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: SignOfZeta on April 06, 2008, 03:09:04 PM
This is very good news. If we can get a source for those little gears for the OG CDROM units, then what else is there left to fix?
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Turbo D on April 06, 2008, 03:16:23 PM
Nat is the man! 8) This thread should be a sticky!
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 06, 2008, 03:41:18 PM
This is very good news. If we can get a source for those little gears for the OG CDROM units, then what else is there left to fix?
It makes me feel all warm and fuzzy to think that my Turbo hardware could last forever with the fixes this board has documented.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: chop5 on April 06, 2008, 06:55:02 PM
excellent!
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Jitawa on April 06, 2008, 09:24:51 PM
Well darn, I have another thing I have to send Nat now.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Keranu on April 06, 2008, 09:50:40 PM
Outstanding!
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Paisa49 on April 07, 2008, 02:57:31 AM
A somewhat related video question, other than actually replacing the entire lcd screen on an Express, has anyone figured out how to fix dead pixels? If not, how expensive is it to replace the lcd screen on an Express?
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 07, 2008, 12:32:50 PM
A somewhat related video question, other than actually replacing the entire lcd screen on an Express, has anyone figured out how to fix dead pixels? If not, how expensive is it to replace the lcd screen on an Express?
I don't know of any sources for the LCDs that the TurboExpress units use. I would imagine they'd be very expensive, if you could even find them anymore.
For dead/stuck pixels, you could always try the "eraser trick" which involves quite literally "rubbing out" the bad pixel. Perhaps someone else who's actually done it can provide a more detailed description of the procedure.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 07, 2008, 02:22:33 PM
It's not really possible to fix dead or stuck pixels because of how they become dead or stuck. Replacing the screen is likely to be a pint-sized nightmare...finding that exact screen is going to be virtually impossible due to its age, and I don't know if anyone's found a suitable replacement yet. But I do remember reading something about someone using one of those portable PSone screens with a TE...
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Necromancer on April 07, 2008, 06:03:46 PM
It's not really possible to fix dead or stuck pixels because of how they become dead or stuck.
That's not entirely true. Dead pixels (where all three sub-pixels are non-operative due to a manufacturing defect) indeed cannot be resuscitated. On the other hand, stuck pixels (where a sub-pixel is permanently on due to a transistor malfunction or to uneven distribution of liquid) can sometimes be fixed with gentle massage (as nat mentioned) or with special software that rapidly cycles different colors on screen. These methods can be quite effective on modern LCDs (PSP, DS, etc.), but I'd be really surprised if it worked on an ancient Express.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 08, 2008, 12:54:18 AM
If the rapid color cycle method could possibly work for the TE, I'll write a piece of software to do it and put it onto a neohucard. It would be great if it could fix the problem.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 08, 2008, 03:40:08 AM
That would probably be a very easy piece of software to write, and if it fixed the stuck pixel issue in even just SOME cases it would be fantastic.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Paisa49 on April 08, 2008, 04:49:44 AM
Man, you guys rock. The dead pixels issue seems to be pretty common with the TE's. Luckily, I'm not having any issues with my TE yet, but it's good to know more people like Nat are stepping up to the plate.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 08, 2008, 05:51:49 AM
My beloved TE recently developed a stuck pixel...I hope it can be corrected.
Yeah nat, it will be braindead easy to write. :) Now it'd just be a matter of getting it onto a card...gotta find a chip supplier, and an efficient method of producing the circuit boards.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 08, 2008, 05:58:02 AM
If you want to just write the program and give it to me as a PCE ROM I can test it because I can put it on my flash cart and do it that way. I have a few units with stuck pixels (stuck red, green, etc) that would be perfect to test. That way you don't have to eat the cost of producing an actual cart if the program doesn't correct the issue.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 08, 2008, 12:37:50 PM
Okay then, give this app a try:
http://www.nodtveidt.net/tefix.rar
and let me know if this is along the lines of what you need.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Joe Redifer on April 08, 2008, 12:47:46 PM
Wow, I didn't know NAT was into modding and the such. Didn't seem like the type.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: SignOfZeta on April 08, 2008, 12:54:40 PM
My friend uses one of those epilepsy inducing flashing programs on a LCD he bought for his computer. It had several dead pixels as shipped, and this program fixed all but one of them, I think. Certainly worth a shot.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Necromancer on April 10, 2008, 04:07:16 AM
and let me know if this is along the lines of what you need.
Nice Express pic. 8)
If this piece of wizardry doesn't work, then I suggest trying one of the myriad offerings for TVs and monitors. Running one of those via a TurboVision might work a little better, since it wouldn't be limited to the Turbo's color palette.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 10, 2008, 05:27:40 AM
Sorry Nod, I've been busy like you wouldn't believe and haven't had a chance to test your program yet. I'll get around to it by this weekend.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 10, 2008, 06:36:42 AM
That sucks...I was kinda hoping you'd run it on my TE before sending it back.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 10, 2008, 06:41:17 AM
Really? You should have asked. :( I didn't even notice any dead pixels on your screen, but then I wasn't really looking.
You might be in luck. Check your PM.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nodtveidt on April 10, 2008, 08:33:36 AM
Dead pixels are unfixable, but stuck pixels seem to be fixable in some cases. As for the screen, I've now managed to tear a TE completely apart, so I can study how the screen works and see if a replacement screen can be used. There's always the possibility of molding new plastic shells and using newer, larger screens, while in the process, reducing battery usage. I'd even like to find a way to attach the backup RAM, but that's more than likely a pipe dream.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 10, 2008, 05:41:52 PM
I'm currently running the program on a PC Engine GT that I own. It has two stuck pixels. So far, no luck. I'm wondering how long I ought to let it run. I'm running it on "FAST CYCLE" right now.
...still no luck, just switched to SLOW CYCLE...
Oh well, no luck. Tried it on two units (one of them was yours). It was worth a try, I guess.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: WoodyXP on April 10, 2008, 08:15:06 PM
Thanks for posting this, Nat. I'll keep this thread in my back pocket in case mine goes bad. *crosses fingers* 8)
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Sinistron on April 11, 2008, 01:49:48 AM
Well I got my express back from Nat yesterday (QUICK turnaround) and I must say :clap: everything is in fine form, screen is working stellar, sound issue is fixed, and Nat even fixed a stuck pixel- a surprise that I wasn't expecting. Played some Hero Tonma on it yesterday and I am a very happy camper.
Thanks again Nat. :D
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: chop5 on April 22, 2008, 05:57:46 PM
did it today works perfect! thanks nat :clap: saved a tg expres from the dumpster. I used a 4.7 50v cap i had laying around the house (was too lazy to go to radio shack)
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: turbokon on April 26, 2008, 10:11:36 AM
Thanks nat. I'm going to add this to my list of services. I hope you don' t mind.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on April 26, 2008, 10:34:00 AM
Ha, of course not. Share the wealth. :D
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Jitawa on April 26, 2008, 11:37:11 AM
I've gotta say, I'm really looking forward to having a working express again.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: imnes on May 12, 2008, 02:40:37 PM
Was attempting this repair and I think I overheated the component, the solder pad for the positive side of the capacitor pulled away from the board. Where else can I attach the positive lead of the capacitor to repair this?
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: chaoticjelly on May 23, 2008, 05:53:16 AM
I actually posted the same information in October of last year, but didn't create a breaking news thread :D
I actually posted the same information in October of last year, but didn't create a breaking news thread :D
Not quite the same information, as nat narrowed it down to a single culprit and provided pretty pictures. :wink:
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Turbo D on May 23, 2008, 11:23:20 AM
I would like to thank Nat for narrowing it down to one capacitor. If it wasn't for Nat, I would have had to replace every freaking cap on that damn pcb! It was an easy fix to do, thanx Nat! :mrgreen:
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on May 23, 2008, 11:28:16 AM
Sure guys, no prob...
And I was gonna say! I actually looked at that thread when I was trying to figure it out, and I was just now about to hit my head against the wall if the answer had been there the whole time and I simply overlooked it.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Duo_R on September 03, 2008, 08:16:30 AM
I see how you remote mount. Is there just enough space to mount SM caps on this thing? Anyone know a trick how to solder SM caps on VS having to use wires?
Also, can you post the list of caps values and quantities that I will need to order (I will probably just want to replace all of them since there aren't that many)?
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Duo_R on September 14, 2008, 10:07:44 AM
Here is how I installed my cap, I am using a technique that doesn't require the use of wires (I realized that you didn't use wires on the video cap, but you can do the same thing for the sound fix).. (http://img68.imageshack.us/img68/1552/0912082250alm6.html)
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on September 24, 2008, 03:09:41 PM
I see how you remote mount. Is there just enough space to mount SM caps on this thing? Anyone know a trick how to solder SM caps on VS having to use wires?
Also, can you post the list of caps values and quantities that I will need to order (I will probably just want to replace all of them since there aren't that many)?
Sub Mini caps will work instead of remote mounting :D That's what I've been using on all the ones I've repaired.
Awhile back I made a cap replacement chart here in the Repair/Mod forum. It's called "Turbo Express total cap replacement chart ". That will give you all the values and quantities you need. I also made one for the Duo too in there somewhere...
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on September 24, 2008, 03:14:36 PM
Insufficient space for the cap is not why I remote mount, it's more a factor of laziness and wanting to avoid dealing with the extremely confining space on the TE PCB. But yeah, you can surface mount to your heart's content. To each his own.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on September 24, 2008, 03:20:14 PM
Definitely! Sorry if that came out sounding rude Nat. I just wanted to make sure Duo_R knew that he/she could indeed just use smaller caps if they didn't want to run the wires.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: nat on September 24, 2008, 04:12:02 PM
Definitely! Sorry if that came out sounding rude Nat. I just wanted to make sure Duo_R knew that he/she could indeed just use smaller caps if they didn't want to run the wires.
Oops, my reply was directed towards Duo_R, not you.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Duo_R on September 24, 2008, 04:35:35 PM
uhh - I am a he, not a he/she. :roll:
Yeah Nat, I actually figured out how to avoid the wires, but then realized that in the original post you didn't use wires for the vid cap (just the audio caps). I am not questioning your work, definitely one of the veteran modders on here.
Now the real question Nat is can u make a good RGB amp??? That is something I have yet to try.
Definitely! Sorry if that came out sounding rude Nat. I just wanted to make sure Duo_R knew that he/she could indeed just use smaller caps if they didn't want to run the wires.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on September 25, 2008, 04:41:15 AM
Nat - No prob :D
Duo_R - Ha! You know what I meant.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: agt_dale_cooper on November 07, 2008, 11:40:58 AM
Confirmed working here...Radio Shit P/N 272-1024, 4.7uF, 35V, $1.19. Can't find anything 35V submini at Parts Express (my new favorite store, thanks again, PCEH), but did find a 50V submini (020-1654) which I think is easier to stash in the CRAMPED space where this thing goes. [Noting along the way that the white stuff is the vicinity of this cap is space-filling FOAM, and can easily be broken off to provide more real estate...] Not sure I want to exceed the original voltage spec, though...will find a way to jam the 35V in (NICE pics, folks!), will test the quality of my soldering job by bending the bejesus out of the leads...now I get to do the audio fix on this thing, because the audio sucks. Yay. [Thrilled smiley omitted]
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Duo_R on November 07, 2008, 01:22:56 PM
I found a way to install the Vid cap pretty easily, even if it is a larger cap. I will post up pictures later, but u just keep the legs long, solder, and then bend the cap over to the other side of the PCB, and almost a 90 degree angle (perpendicular to the board on the other side) this fits nicely into a space in the system housing. It is a snap to install this way.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: agt_dale_cooper on November 19, 2008, 11:58:24 AM
Correction: Parts Express 50V submini is 020-1634. Fits in space provided without having to bend the bejesus out of anything...hope the higher voltage doesn't screw anything up...
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Windsor75 on February 11, 2009, 09:04:30 PM
Hello :)
Because it's my first message, I'll introduce myself a little. I'm 33 and just came in the "Nec World" I didn't know. I bought two months ago a Duo-RX and some weeks ago a GT.
This GT needed one or two minutes of "warm up" before the screen displayed the game clearly. I read this topic, and thought about replacing the cap at the top of the mobo. But because I never did this kind of stuff, I didn't.
But sadly, yesterday evening, after I played a game, I turned it off and on with another game, but the screen never turned on. I only had the backlight.
So, I have two questions, before I try to repair it : - I suppose that changing the cap could fix it, am I right ? Or is the screen dead ? - Is it difficult to do for someone who never did it ?
Thanx for your answer
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on February 12, 2009, 02:07:25 AM
Hey Windsor, welcome aboard.
Having a backlight but no picture definitely sounds like the issue discussed in this topic.
As far as whether or not it's difficult really depends on your level of experience with electronics. If you have used a soldering iron before and have some familiarity with circuit boards then you should be good.
If not, then I'd suggest practicing on some broken circuit board or buy some project board from Radio Shack. You can look on Youtube or do a google search for "proper soldering" or "soldering techniques" or something like that to get some good instructions.
Use a 15 watt soldering iron to be safe (which you can get from Radio Shack for around $8 if you need one).
It's not hard once you get familiar with soldering, but I'd highly recommend having a little practice under your belt from a different pcb before you work on this one.
Good luck!
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Windsor75 on February 13, 2009, 02:07:30 AM
Hi Red Ghost,
Thank you for your advice. I think I'll train on an old VCR I have before fixing my GT !
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on February 13, 2009, 03:45:05 AM
Sounds like a great idea. Let us know if you need more help/direction.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: ColterF on February 24, 2009, 11:22:18 AM
Nat/ Punchy Pedo,
Did the backlight work before you fixed it, did you games have audio, I'm having a similar issue but not sure if its the same, my TE will turn out, the backlight goes on, but no sound, no picture.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Duo_R on February 24, 2009, 01:32:51 PM
I have done a good amount of TE's, and I have seen bad sound, bad video, and bad sound AND bad video cap Turbo Expresses. It is extremely rare to find one that truly has a bad screen. In this lot that I fixed, one of them had bad sound, and when it arrived at my door from the owner, it also had bad video cap. My advice is to just replace all the caps (related to sound/vid) while you have it opened.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: ColterF on February 25, 2009, 05:26:00 AM
Duo R,
Thanks for the advice, I figured I might a well get em all fixed, now my only concern is where to do it, I'm terrified it would result in some sort of explosion if I attempt it. I've never soldiered in my life, but buddies of mine have, on a scale of 1-10 what do you think the difficulty is for the job? I've opened it up and it all looks fairly accessible/
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on February 26, 2009, 02:16:40 AM
ColterF - If your friends can do quality work with a soldering iron then you'd be set. As long as they are familiar with small electronics it isn't a very difficult job.
Just make sure they know what they are doing and, if need be, have them practice removing/replacing caps on a broken pcb.
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: pceslayer on February 28, 2009, 10:53:26 AM
I found this forum over a year ago while scowering the web for a replacement laser for my original TGCD and I just wanted to say, Thank you guys!
I got a Turbo Express from a guy online as-is with 5 games for $30... Issue was Sound and backlight, but no video.
Wen't to radioshack and bought the cap and 20 min later I had a working turbo express!!
Thanks again! :clap: :clap:
Title: Re: Breaking News! TURBOEXPRESS / PC ENGINE GT VIDEO FIX!
Post by: Platinumfungi on March 04, 2009, 04:31:11 AM
I have made this topic sticky, as well as changed the thread title for better classification.
Awesome. Thanks a lot!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ColterF on March 12, 2009, 09:09:41 AM
I spoke with Duo_R a few times and he was kinda enough to offer to fix my express. I shipped him the TE and for a very reasonable rate fixed all my caps AND my lousy torn run button. I couldn't speak highly enough about Duo_R, very nice, very fast and very professional. If you need your screen, keys, sound, caps fixed, Duo_R is the guy to pull it off.
Thanks again Duo_R, I'm playing TE like it's 3rd grade all over again! :clap:
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Bludgeon on June 23, 2009, 06:16:41 PM
Sounds like the deal to me and wondering already from whats been shown if my TE has the same video problem discussed here? It has a greenish hue and thats about as far as it gets. It would be nice if the TE guru here could fix it since the one thing I did the most on it was watch tv but since analog is no longer a viable source of video it might be nice to play Devils Crush on it once I find it again.
Blud
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: DragonmasterDan on June 25, 2009, 10:18:44 AM
I've yanked apart my TE and found the infamous cap in question. What's the best/safest way to remove it? Any suggestions. this will be my first attempt at a soder repair.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: DragonmasterDan on June 26, 2009, 11:35:22 AM
I've yanked apart my TE and found the infamous cap in question. What's the best/safest way to remove it? Any suggestions. this will be my first attempt at a soder repair.
I tried solder repairing a game gear today. Unfortunately it didn't work despite looking good. I may hold off on this one for a bit.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on June 26, 2009, 08:33:50 PM
Man, the TE video fix couldn't be easier. Just make sure you get the polarity right, or you could really f--- things up. Use a pair of needlenose to carefully remove the old cap (be gentle so you don't lift the traces off the PCB), then solder the new one in place. The location of the video cap makes the job particularly simple since it's right on the edge of the board and easy to get to.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: samson7point1 on July 22, 2009, 08:00:49 AM
Thanks for the awesome repair guide. I snagged a practically brand new TE off of Ebay for $34 and managed to fix it with a $1 part from Radio Shack.
It got a little hairy there for a bit though. I thought I was being careful but still accidentally pulled the negative trace off the board when I removed the capacitor. Thankfully the trace ripped pulled up far enough for me to follow it to another solder point. The leg of the little transistor/MOSFET that sits just adjacent to the cap will work.
If I had it to do over again I would definitely have tried to touch the soldering iron to the legs and gently pry them up rather than trying to pull the cap off cold.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=363;image) Looks so innocent just sitting there.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=365;image) Disaster strikes! I did not notice the little trace that was ripped out of the surface of the board at first - I honestly thought it was just a strip of paint or glue or something. The scratches you're seeing where the pad for the negative trace was are my desperate attempts to find what the pad had been attached to. I was hoping that if I dug into the board I would find another solder point. I realize at this point that was silly, but at the time I had no idea.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=367;image) But that was exactly what I needed to find an alternate soldering point.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=369;image) Here is the alternate soldering point magnified some more.
I decided to remote-mount the cap because the connections, while solid, were so fragile I didn't want to risk any more bending and twisting than I had to. It may not be pretty but it works like a champ.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Necromancer on May 11, 2010, 10:27:33 AM
My turbo express is slow to power up, meaning the screen takes a little time to show clearly any ideas?
Dying capacitor(s). Eventually it will never 'warm up'..... just like mine. :(
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 21, 2010, 11:13:25 AM
Similar problem on this same topic though. What should one do if your screen works perfect, but the backlight progressively gets brighter the longer the unit is on, even though you've turned the brightness to the minimum?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: osmodiar on August 22, 2010, 05:23:00 AM
I have done this and my video works but now it is slowly grows darker and darker and then cuts out. I have been at it for nearly a full 24 hours now. I give up! What to do next? anything? ugh!!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 22, 2010, 05:50:51 AM
I have done this and my video works but now it is slowly grows darker and darker and then cuts out. I have been at it for nearly a full 24 hours now. I give up! What to do next? anything? ugh!!
I guess your turbo express and my turbo express need to get together :P Mine gets progressively brighter!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: osmodiar on August 22, 2010, 07:42:59 AM
Well, interesting story about that. It did that too but then I replaced a couple other caps and now as it warms up it starts to flicker and get darker and darker until it simply shuts off. So, I got the good one out of my personal collection which I had purchased new from tzd a number of years back. Just so I could feel god about playing one that I new to be working. I had only used it a handfull of times. I fired it up and much to my horror the sound was very low and as I allowed it to play further the screen got darker and darker but didnt shut off completely like the other one. So, I went and got some new caps. now with both the sound cap and the video cap in place my good one is now getting lighter and lighter. Holy crap!! I mean really! why is it that the coolest toys are always crap? I realize I am new on this forum but if anyone can help me out it would be greatly appreciated!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 22, 2010, 07:44:29 AM
I'll probably just start replacing every cap on the unit until I figure out which one causes the brightness issue
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: osmodiar on August 22, 2010, 08:43:20 AM
do you think it will be simply that? I see from the step by step at the beginning of this thread it says that the one that ended up correcting the issue was the last one that was changed. But given the troubles we are having it dosent seem that it is solely the culprit. so, replacing them all does make sense but ugh! what a job!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 22, 2010, 10:12:41 AM
I think the issue they were referring to was the backlight on but no video issue. I suspect our backlight issues are tied to a different source, be it a bad cap or something else.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on August 22, 2010, 04:56:13 PM
The brighter and brighter issue usually means you are using sub-par (or almost dead) batteries. The Express seems to be finicky-- it wants good, quality name-brand alkalines to work right. It doesn't like any sort of rechargeables or non-alkaline sources.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 25, 2010, 12:18:46 PM
The brighter and brighter issue usually means you are using sub-par (or almost dead) batteries. The Express seems to be finicky-- it wants good, quality name-brand alkalines to work right. It doesn't like any sort of rechargeables or non-alkaline sources.
Looks like you nailed it! It had some cheap off brand batteries in it, so I swapped in some fresh brand new energizers, and now it works perfectly!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on September 12, 2010, 05:16:31 PM
i currently use nickel metal hydride rechargeable batteries with no problems, however i recall the manual saying to stay away from nickel cadmium batteries.
The brighter and brighter issue usually means you are using sub-par (or almost dead) batteries. The Express seems to be finicky-- it wants good, quality name-brand alkalines to work right. It doesn't like any sort of rechargeables or non-alkaline sources.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on September 12, 2010, 05:34:14 PM
I've never personally tried nickel metal hydrides in an Express, but I've tried [fully charged] nickel cadmiums and I only got about 6 minutes of play before the "brighter and brighter" syndrome set in.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on September 12, 2010, 06:22:22 PM
yeah hydrides are legit, I get like 4 hours out of a set that I have.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on October 15, 2010, 04:01:00 PM
I was replacing the cap on a TE and I accidentally pulled both solder pads while desoldering the old one. I can't find the traces they were connected to and I need to know what points I can solder to instead.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on October 15, 2010, 04:30:52 PM
For which cap, the video one? Pix?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on October 15, 2010, 04:47:42 PM
Yeah, it's the video cap. I'll see if I can provide a pic on Sunday, since I'm busy tomorrow.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on October 24, 2010, 11:37:46 AM
Ack, wasn't able to get a pic, but I don't think I need one since both the pads for the video cap are gone. I need to finish this repair, so I need to know what other points I can solder the cap to.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on October 28, 2010, 06:43:18 PM
Anyone?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: blueraven on October 28, 2010, 06:55:33 PM
First we would need a photo. If you upload a picture, It would be easier for people to instruct you. Also if the pads are gone are the traces gone as well?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on October 29, 2010, 05:00:52 PM
Finally got my camera to cooperate...
(http://i51.tinypic.com/zv1sic.jpg)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: blueraven on October 29, 2010, 07:03:33 PM
ApolloBoy,
These are the two areas that you are going to want to focus on, the positive terminal for the video cap in the blue circle, and the negative solder-point for the capacitor that should be under the pink oval.
On the positive side; Inside the circle is what is left of the trace, I'm assuming. In the right-side of it, is that what's left of the copper trace that led to the pad? If so try to solder the positive side of the capacitor to this. If there is enough of the trace left, but you cant get the leg of the capacitor to attach to the delicate trace, solder a very thin wire like 24 AWG or smaller on one side to the trace and on the other side to the positive leg of the capacitor. If the trace is too far gone, try to attach the positive leg of the capacitor to the hole that I have highlighted with a black dot inside of the blue circle.
On teh negative side; Veeeery carefully scrape with a 1/16" screwdriver in the area under the pink oval. I did this on my express and I saw a solid copper line leading up to the pad. You may want to do the wire trick again. I'm not sure if this is a specific area where you need to ground the cap.
I hope this helps you get you system back online; people please chime in :mrgreen:
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on October 30, 2010, 02:09:55 PM
when I get a chance I will check my TE to see if there is another option.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 01, 2010, 12:58:10 AM
Apollo did you see the post on page 5 where the same issue happened?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 01, 2010, 04:39:08 PM
Uploaded with ImageShack.us (http://imageshack.us/)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: chop5 on November 02, 2010, 07:40:56 AM
this has poyplexed me. it looks like the right cap prong goes into the middle pin of that tiny voltage regulator on the far right but the left pin i cant figure out. i think it goes into the bottom of the board into that blue thingy. i need to see how the circuit flows.
but yeah this is a common problem with me. the smaller a cap is the greater chance of the whole pad either coming off or solder lifting up. The cap fluid eats away at it making it very brittle. the 4.7 and the 33 uf caps are huge problems. of course the 100uf caps are biger and have more solder so no problem.
The best way for me to remove one of these caps is to use a small screwdriver and gently rock the cap back and forth where it gives way till it frictions off. if it leaves behind its old cap legs thats gold,easier to solder onto. flipping the motherboard to rest on the case makes it easier and wont harm it.
(http://pic.photobucket.com/bwe.png)
its takes about 15 to 20 minutes to rock it back and forth. it can move real fast like a blur but it gets boring but if you close your eyes and say the buddahist sutras the time will go fast.
i shape my caps legs for soldering first:
(http://pic.photobucket.com/bwe.png)
but apollo if the soldering welds are too tiny for you to do il do it for you for free. Solder paste or flux is like gold,makes tiny welds possible :wink:
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 02, 2010, 03:13:20 PM
15 to 20 minutes? Try five seconds with needle nose pliers. Just do the twist back and forth.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 03, 2010, 10:49:50 AM
I seem to be having troubles with this. I think the trace for the negative side is gone and now I need to know what to solder onto now. The positive side is fine now, though.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 03, 2010, 11:14:35 AM
Dud u see my post?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 03, 2010, 12:09:36 PM
It is a little blury but negative goes to the pin marked on the diagram of the chip marked BA.
I just tried that and it still didn't work. As for the positive side, can I solder onto one of the pins on that component underneath the 100 uF cap?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 03, 2010, 06:57:56 PM
Pics of what u are doing?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: chop5 on November 03, 2010, 07:06:39 PM
yeah i could use pliers but these caps and the connections are so small il risk tearing off the pad,solder or both. Thats why with friction i hope to leave part of the leg for me to solder on. But sometimes the cap fluid corrodes it so bad the cap can just come off with a touch taking with it the precious solder leaving bare pads. If this happens to you guys don't worry. If theres just a little bit of solder on the pad you can run a drop of solder from your iron tip to add more. if theres absolutely no solder getting solder to hold wont be a problem. The best way is to put solder paste on your cap leg and pad then a drop of solder from your iron. The solder wont stay on the pad without the metal from the cap leg to react with it. Its like witchery but will hold :wink:
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 08, 2010, 09:35:10 AM
I want to know if I can solder onto one of the legs of the component circled in blue. Right now I'm trying to solder onto the trace located on the orange circle but it's a no go. (http://i54.tinypic.com/2mpyfer.jpg)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 08, 2010, 11:32:07 AM
Again see the diagram I posted or pm me if you want me to repair
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 13, 2010, 09:09:11 AM
Again see the diagram I posted or pm me if you want me to repair
That didn't really answer my question though. Can I solder onto one of the legs of the component circled in blue, and if so, which one?
I'm confused, ApolloBoy. Below is the photo that has the correct solder point. I'm assuming your photo is Duo_R's blown up. On the previous page we have outlined the areas that you can solder to to correct the broken traces. Duo's diagram is about as concise as you can get.
What makes you think you should solder to that chip?
Exactly. The answer is no, you should not solder to that chip.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 14, 2010, 03:45:03 AM
Apollo do you have experience with soldering electronics? If not send to Chops (he already offered to you for free) or I can take a stab at it. I think I already spent way more time sending diagrams, etc that it would have taken me to have just done it already. lol
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 14, 2010, 05:13:08 AM
I'm confused, ApolloBoy. Below is the photo that has the correct solder point. I'm assuming your photo is Duo_R's blown up. On the previous page we have outlined the areas that you can solder to to correct the broken traces. Duo's diagram is about as concise as you can get.
This is just weird, because I've tried every area you and Duo_R have shown, and I'm still not getting any video.
Apollo do you have experience with soldering electronics? If not send to Chops (he already offered to you for free) or I can take a stab at it.
I've got plenty of experience with soldering. I've done mods and repairs for people and I've replaced the caps in two Game Gears and another TE, among a few other things. I can do this, it's just that this TE is being frustrating to work on right now.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on November 14, 2010, 05:21:29 AM
I think we all run into one piece of hardware that kicks our butt. I had a turbo CD do that to me... its now been hacked up to save a few other turbo CDs :P
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 14, 2010, 05:31:36 AM
Sorry if you already stated this but has video ever worked on this unit since you had it? Why were u replacing this cap to begin with?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: blueraven on November 14, 2010, 06:31:51 AM
I think we all run into one piece of hardware that kicks our butt. I had a turbo CD do that to me... its now been hacked up to save a few other turbo CDs :P
I agree. I have a duo that is in chop5's care even though I have replaced every cap, the laser, the motor, and the headphone port.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 14, 2010, 09:24:04 AM
Sorry if you already stated this but has video ever worked on this unit since you had it? Why were u replacing this cap to begin with?
I'm actually fixing this for a friend of mine, who bought it on the cheap and found that it didn't work. When I opened it up, I found that most of the caps on the unit had leaked and needed to be replaced. I've succeeded in replacing all of the caps and getting every part of the system working except for that one video cap. My friend actually tried to replace a few of the caps, including the video cap. He didn't do that great of a job replacing them (and admitted this to me beforehand), hence why it still wasn't working when I received it, and hence why both the solder pads for the cap got lifted when I tried to redo it.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 14, 2010, 09:55:40 AM
Have u swapped screens with another unit to confirm the screen isn't bad?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on November 14, 2010, 12:36:58 PM
Have u swapped screens with another unit to confirm the screen isn't bad?
I have a TE of my own, so I suppose I could give it a try. I'll do the swap tomorrow and see how it goes.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 14, 2010, 01:20:42 PM
Give that a shot, swap screens on both units and see what happens
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on November 15, 2010, 01:02:54 PM
Are you sure the unit is even powering up? Do you hear sound? Sorry if you answered this already back there, I'm way too lazy to backtrack through messages.
If your friend f*cked something up when he was haphazardly replacing caps, he could have easily blown the unit's fuse. It goes south at the drop of a hat. Trust me, I've been there.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: stimpy on November 22, 2010, 08:47:26 AM
Hi People!
alas - I was so happy when I found this repair guide, because my PCE-GTE had exactly the symptoms described here (backlight + sound but no piture). I have thorougly followed the instruction and replaced the capacitator. Unfortunately the problem did not go away. The cpacitator seems to be firmly in place. Any hints? :(
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 22, 2010, 09:03:24 AM
need more information to really give some guidance. Did this unit work before for you? Did the install go smoothly? Do you have pics of the install area?
alas - I was so happy when I found this repair guide, because my PCE-GTE had exactly the symptoms described here (backlight + sound but no piture). I have thorougly followed the instruction and replaced the capacitator. Unfortunately the problem did not go away. The cpacitator seems to be firmly in place. Any hints? :(
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: stimpy on November 23, 2010, 09:13:24 AM
Yes the unit did in fact work before. However the display went dark after some time leaving the backlight on. When I removed the old capacitator, it seemed that it had actually bled. Please have a look at the picture, to check if the new cap is correctly installed. For me it really appears to be.
need more information to really give some guidance. Did this unit work before for you? Did the install go smoothly? Do you have pics of the install area?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on November 23, 2010, 06:27:04 PM
The thought occurs that one of the solder pads may have inadvertently been removed when you took off the old cap.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: stimpy on November 23, 2010, 08:34:59 PM
I that turned out to be true - can you think of a way to fix it? Thanks.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 24, 2010, 05:25:52 AM
If you did we can find somewhere else to solder. But need to know specifics.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: stimpy on November 25, 2010, 12:29:25 AM
OK then - after having a closer look, i would say that the left pad (see picture above) is still in place. If you look at spot where the left pin of the cap is attached to the board - you can notice some black spots around the solder. That may indicate that the right pad was in fact lifted. I bought a desoldering wick today. Should I detach the new cap?
No - I'm not a soldering freak to be honest. Perhaps a friend of mine can lend me one.
Also - of course in my last post I was talking about the _right_ pin having black spots around the attached area - sorry.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 28, 2010, 09:11:15 AM
I bought a cheap one at Harbor Freight.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on November 28, 2010, 09:33:55 AM
You should be able to pick up a cheap one at sears for less than $20 also.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Duo_R on November 28, 2010, 10:56:44 AM
I don't hardly recommend this, but if you are on a budget and have a store near you would be worth it just to check out your problem. just be warned it is a cheepie.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on November 29, 2010, 10:46:27 AM
As an FYI, there are already two places on the board that are ideal spots to connect the new capacitor. To find them, draw (mentally, of course) a line between the center of CC500 and CC501. The location is half way down that line, almost dead center between the two caps. Note that one is a hole; the other is a TestPoint that is covered with solder. But it's still a good mechanical connection.
The positive of CC501 goes to the hole close to Q500, the negative goes to the test point close to D502. Based on the picture above, it looks like you have to dig out the latex to see them!
Picture showing open hole (positive connection) and test point(negative connection): (http://i721.photobucket.com/albums/ww214/charliee1151/IMG_0810_small.jpg)
Charlie
(Edited 12/1)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: ApolloBoy on December 14, 2010, 09:39:01 AM
Give that a shot, swap screens on both units and see what happens
I finally got around to swapping the guts between my friend's TE and my TE (which was easier than swapping the screens, and the screen is not the issue. Something must be seriously wrong here since I've tried everything to get the video working on this unit.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: cornacchia on January 03, 2011, 04:30:18 AM
Hey everyone, so ApolloBoy tried to fix my turboexpress and could not get it going. I was wondering if anyone else would be willing to look at it and see if they could do anything.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on January 04, 2011, 01:17:22 PM
I dont mind giving it a shot. Let me know :) Or alternately, chop5 is a magician when it comes to this stuff :P
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on February 13, 2011, 10:57:00 AM
Rather than start a new topic, I thought I'd post this here. Question mainly aimed at Charlie, since he seems to have these PCB layouts down pat:
I've got a GT PCB that has an odd problem. Something on the board is causing the LCD backlight to "pulsate" while the unit is on. Pulsation happens the same on both battery and AC power. It's really quite distracting while playing, and I'd like to isolate the cause but so far have been unable. The problem is definitely on the PCB itself rather than in the LCD/backlight assembly, as I have several TurboExpress and PCE GT units that I've swapped the PCB into and the problem definitely follows the PCB.
I haven't replaced all the capacitors on the PCB, but I've replaced all the ones I know to be related to the video. Doesn't mean there aren't others that I'm unaware of, however.
Ideas?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on February 14, 2011, 06:02:19 AM
Typically, the pulsation occurs because of: 1. inadequate power. on batteries, you may have dead batteries (DUH!), but on AC you should not have that with an adequate power supply. Make sure the power supply you are using has enough current to handle the TE. I'd go at least 20% above the TE specs. (Edit: you can often tell this is the problem if the pulsation occurs more strongly when any loud sound effects occur. Turn the volume up full and see if you can see a correlation between the pulse and the audio) 2. bad cap (or possibly other part) on the display high voltage line. The high voltage is some 200+VAC generated by an inverter circuit. This circuit needs not only a really heavy voltage source, but a really "clean" (ie, noise-free and ripple-free) source as well.
We'll need a VOM or 'scope to go further.
Charlie
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on February 14, 2011, 02:05:50 PM
Typically, the pulsation occurs because of: 1. inadequate power. on batteries, you may have dead batteries (DUH!), but on AC you should not have that with an adequate power supply.
This problem has been going on for a number of years, through countless sets of batteries.
Quote
Make sure the power supply you are using has enough current to handle the TE. I'd go at least 20% above the TE specs.
I'm using the OEM TurboExpress AC adapter. Works fine/without issue with the other GT/TE units I have.
Quote
(Edit: you can often tell this is the problem if the pulsation occurs more strongly when any loud sound effects occur. Turn the volume up full and see if you can see a correlation between the pulse and the audio)
Will do... This I have not done.
Quote
2. bad cap (or possibly other part) on the display high voltage line. The high voltage is some 200+VAC generated by an inverter circuit. This circuit needs not only a really heavy voltage source, but a really "clean" (ie, noise-free and ripple-free) source as well.
We'll need a VOM or 'scope to go further.
I've got my VOM ready!
Also, one thing I noticed I failed to mention... It only happens after the the unit warms up. The first 30 minutes of play are pulsation-free. This is what points me in the direction of a bad capacitor somewhere....
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on February 14, 2011, 07:13:01 PM
There are either 4 or 5 caps in the inverter circuit. Plus a coil, a transformer, a transorb/PTC, and a few other things I don't remember. Yes, caps is the obvious choice.
Three other items.... 1. Does the pulse change if you tap or bang on the PCB, particularly in the inverter circuitry? 2. Does the whole screen pulse at once, or does the pulse "travel" in a wave up/down the screen? 3. Does playing with the contrast control make any difference to the pulse? Obviously, it WILL affect the display contrast overall!
Charlie
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on February 14, 2011, 07:20:16 PM
There are either 4 or 5 caps in the inverter circuit. Plus a coil, a transformer, a transorb/PTC, and a few other things I don't remember. Yes, caps is the obvious choice.
Three other items.... 1. Does the pulse change if you tap or bang on the PCB, particularly in the inverter circuitry?
Will get back to you....
Quote
2. Does the whole screen pulse at once, or does the pulse "travel" in a wave up/down the screen?
The whole screen. It seems like it's the backlight that is pulsating and not the image itself, although I could be wrong.
Quote
3. Does playing with the contrast control make any difference to the pulse? Obviously, it WILL affect the display contrast overall!
No, aside from the intended effect of using the control.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on February 15, 2011, 01:46:04 AM
At a quick glance, active caps are CC501, C502, C501, C500,C504....but I don't think all of them are electrolytic.
Also involved: D502, Q500, R500, L500, DZ500, Q501, D503...but I would put them at a lower expectation of failure.
You might want to check the backlight voltage at the connector, see if the VOM shows a fluctuation that matches the pulses. Probably yes.
Charlie
Edit: Also involved CC900, C901, CC901, T900, L900, D902.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on April 16, 2011, 08:21:48 PM
although unlikely a failing lamp can cause pulsation, typically after warmup.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on April 17, 2011, 12:28:27 PM
Like I said, the problem follows the logic board. I moved the logic board from one GT to another GT (with a completely different backlamp) and the issue follows the board.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on April 17, 2011, 01:13:53 PM
ceramic cap failures are not unheard of in inverter circuits. did the problem occur with or without use. if it developed the prob on the shelf it will be electrolytic caps, due to drying.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on May 30, 2011, 09:02:18 AM
found the cause of the top left part of the screen too bright. the 100uF 16V cap by the fuse was bad
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 29, 2011, 06:02:44 PM
Right now, my friend and I (more him actually) have checked the board and the 4.7uF 35v contacts are all right. And testing it with a multimeter shows proper current to and from it, through the board. The thing is, now he's trying to nail down a problem with the LCD. He's tested the power circuit that routes power to the LCD. (forgive my caveman terms) It's one of the cables you stick into the red port on the board. He keeps saying that the contacts at 4.7uF 35v are all fine, but the multimeter shows no power going through that red "teethy" port, hence the LCD isn't getting the power it needs. We turn on the TE and the audio works fine, even the start buttons (with the help of sound cues) get us past the start screen, but still no video coming out of that LCD. So he may be right.
Any ideas? Are we on the right track?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on August 29, 2011, 09:17:33 PM
the lcd has a florescent backlight. is the backlight working?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 29, 2011, 10:55:06 PM
the lcd has a florescent backlight. is the backlight working?
How can you check that?
Right now, we're pretty stumped on our problem. Still not getting any successful video out of the TurboExpress. Will be taking photos of both sides of the boards & will attempt to translate (he's not very fluent in English) what my fix-it friend needs to know from this forum. I hope you guys will be able to help. :)
He's been able to test & is almost positively sure that both the 4.7uF 35v cap itself and the traces on the board around that cap work out just fine, so it's not that problem.
Off the bat though, he was wondering if anyone here has a diagram of the board and the leads that go around it. He's tried to isolate where the problem is, and it seems that the "red teethy port" I mentioned earlier is not giving power to the screen. Does this make sense?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 29, 2011, 11:29:31 PM
Ok, still no video and I've included 4 pictures for reference.
(http://img832.imageshack.us/img832/6831/img2356p.html) My best closeup of the 4.7uF 35v cap, in case any of you spot something we don't.
(http://img97.imageshack.us/img97/5074/closeupofproblem.html) Closeup of our problem spot (Everything that's within the yellow border is our problem, front and back. help.. :pray:)
Ok, of what I have been able to glean from my fix-it friend, is that if you look at the last photo, the "red teethy port" is not giving any power to the screen. He's tested the light blue cap that it's connected to on the other side, and he says that the current is just fine, so it should be working. Also, I've highlighted (in a pink rectangle) 5 studs that he wanted me to point out to you guys. I'm not sure why, but he seems to say that there's a problem he can't isolate around these 5 studs. Please meet me halfway in trying to understand what he's saying. He's pretty brilliant, if you ask me, he just doesn't think in English, so let's all try to see how we can make it easier for me to translate what you guys say to him.
Ok, from what I was able to gather from the "dead end" that he's hit, he's asking 2 questions:
1. (See the last photo, pink arrow) What is feeding this port it's power? Where is this port supposed to draw its power from? I think he needs to know the route and source so he can isolate where the problem is.
2. What's the voltage requirement of this red port? He figures if he knows that much, and he can't properly route power to it, he can find a way to cheat and get power there another way. Now whether this is a good idea or not, I hope you all understand that we've tried to test every cap the whole day and nothing is helping.
Any help would be MOST appreciated. :)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on August 30, 2011, 05:14:32 AM
that port provides high voltage AC to a flourescent lamp. the purple hilighted studs appear to be the transformer/balast for the lamp. the two 100uf 16V caps next to the transformer provide the power for 2 transistors that drive the transformer.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 30, 2011, 07:41:31 AM
big help! thanks thesteve! whats the voltage requirement for that port?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on August 30, 2011, 10:05:31 AM
not sure on voltage, likely 600V+ with no load, dropping to around 30V once lamp starts. the only way to test it is with a lamp.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on August 30, 2011, 10:27:40 AM
He is checking for AC, right? Not DC? And the value can be anywhere between 100V and 300V; typically 225V.
Charlie
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 30, 2011, 02:58:06 PM
Thanks guys! I forward the info to him and...well, we'll see what he can whip up. Anything you guys have been able to gather from the photos? Or if you need specific photos of my board?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 30, 2011, 08:33:44 PM
Ok, with your help & some more tinkering, he was able to locate the source of the problem! When we first opened up the TurboExpress, we noticed a massive amount of leakage all over the board. It was really wet. We thought to simply clean it up and hoped none of the leaks affected any of the other components. While everything still seems alright, he's finally deduced that the transformer for the lamp (the one we've been talking about above) seems to have shorted out. All the traces and components leading up to it, and after it seems fine, but that transformer is what's dead.
Does anyone know where I can source this from? I have a feeling that if we can replace this one piece, my Turbo Express will be back up and running. :)
Any ideas? Anyone here have the part?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 31, 2011, 12:30:23 AM
Is that transformer just for the flourescent tube for back light? Worst case maybe you could rig up an LED array as a replacement backlight.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on August 31, 2011, 05:12:20 AM
yes its just for the backlight. yes an LED array would work. id be surprised if its a bad transformer
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 31, 2011, 05:42:00 AM
I'm really stumped at this point. But if the backlight lamp was the only problem, wouldn't I be able to see graphics on the screen? Kind of like how the non-backlit Game Boy Color used to look like?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: BlueBMW on August 31, 2011, 06:24:13 AM
Its very hard to see without a backlight because there isn't much behind the screen to reflect light back at you. A flashlight right on it may work but it still wont be easy to see.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 31, 2011, 06:25:39 AM
I wish I knew what was wrong with this little (read: ginormous) unit of mine. It's really frustrating to keep hitting dead ends, especially when all of the tricks everyone here has tried with their own TEs have worked, but just not with ours.
Plus, to send it over to any of you more experienced techs may cost more, collectively, than to just buy a brand new one.. :(
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 31, 2011, 02:49:10 PM
We were able to remove the transformer from the board. Should we:
1. ...put it back and try to buy a new 4.7uF 35v cap in case it was really just a bad cap all along? :(
2. ...try and look for a transformer piece like this? I'm just worried about getting the voltage wrong or something.. :(
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on August 31, 2011, 02:58:14 PM
2 things.... 1 was there cap juice under the transformer? if so clean and reinstall. 2 with it installed look for any signs of light on the screen (preferably in a dark room) if no light at all its the backlight circuit (transformer, transistors, resistors, capacitors and lamp) the only one i have heard of having a backlight circuit failure, had a damaged trace caused by the guy replacing the caps. repairing the trace fixed it.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on August 31, 2011, 04:11:47 PM
I just forwarded your helpful tip to him, thesteve. Thanks so much for not giving up. I'm sure we can find what's wrong with this. I wasn't around when he was working, so he might have very well damaged that very trace. I'll ask him to be careful this time around and to see if the trace is damaged, or if he had indeed damaged it.
Will update after we reinstall and reevaluate. Thanks!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on August 31, 2011, 09:47:18 PM
It is VERY possible for the xfmr to appear bad if there is capacitor acid on the board, at or near the terminals. The acid is conductive, the backlight power is high voltage and low current; any type of capacitor gunk in the circuit will simply short out the high voltage. I'd make sure the entire area around the transformer and related circuitry is absolutely clean before I'd assume the xfmr is bad.
As a test, you can temporarily connect just the primary (input) side of the xfmr to the circuit, leave the secondary (output) disconnected, and then check the voltage. That will tell you if the xfmr is good or not.
Charlie
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 01, 2011, 01:13:05 AM
Just got home and spoke to him:
He made a rough map of what the transformer looks like (hope this shed some light for a solution to present itself):
PRIMARY SIDE SECONDARY SIDE 1 - live 1 - dead 2 - power supply 2 - dead 3 - live 3 - dead 4 - live 5 - ground
And he assumes that the main power line runs between Primary 2 and Secondary 3. Is this correct?
Does the above make sense to you guys?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 01, 2011, 05:13:49 AM
the transformer will not have a connection from the primary to secondary. the way it works is by running pulses of current through the primary coil, magneticly inducing voltage in the secondary. on most you will also hav a feedback coil in the transformer, used to drive the transistors. the transistors will short the primary coil to ground at a resonent frequency, driving the circuit.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 01, 2011, 07:50:07 AM
I'm sorry, but I think we got a little lost in translation.. :p Your whole explanation went over my head. But by the sound of your answer, it's possible that I might have translated his diagram wrong as well. You see, I'm sure he knows how a transformer works, so it's probably just wording from me (ak! Sorry!)... But what do you think we ought to do at this point? And if possible... In easier English so I can explain it back to him. :s
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 01, 2011, 10:05:43 AM
I was just explaining how the transformer works, and how the circuit works. I have not traced out the circuit, so i cant go in to detail on what to check. if i had a schematic, i could walk you through it.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 01, 2011, 04:17:12 PM
Does a schematic of this express/gt exist?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 01, 2011, 05:03:13 PM
i dont know i could do one, but charlie is better at it
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 01, 2011, 11:44:42 PM
I think at this point, a schematic seems to be the only way for us to really locate where the problem lies and if it can be remedied. If you or Charlie could post one up here, I'd really appreciate it.
Update: My tech friend who has been working on this unit says he's tried to shine a light onto the screen and he doesn't see any graphics moving on the LCD either. The sound & power works fine, but he doesn't see anything on the screen, even unlit. He thinks that the LCD screen doesn't just lack power from the transformer, but it doesn't even have any graphics coming out of it.
:cry: This is getting really deflating..
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 02, 2011, 05:14:43 AM
now that is what the cap issue has always been.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 02, 2011, 08:56:22 AM
The Cap Issue... i.e. leaking out to damage other components?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 02, 2011, 10:10:17 AM
the cap issue is 2 fold. the caps open up, and eat traces and feedthrough's opening circuits. the cap juice is slightly conductive, and only likely to directly effect high voltage circuits directly. the duo is notorious for requiring traces and feedthrough's repaired after the caps are replaced, before they work properly
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on September 02, 2011, 02:41:38 PM
Without going back and reading 5 pages, let me ask.... Did you actually replace the video capacitor? If not, why not? It can look "just fine" and not be.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 02, 2011, 02:59:09 PM
yes its a full cap change. (just looked at the pics) take a close look at C900 (its a ceramic cap on the back of the board, by the transformer)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 04, 2011, 07:16:25 AM
So everything looks fine, doesn't it? This is why it's so damn frustrating.. you guys think it might really be a bad transformer or a bad screen? Or worse, both...?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 04, 2011, 07:43:32 AM
id suspect you either had no pic or no backlight, not both
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 04, 2011, 07:54:33 AM
I think it's backlight. As my tech-friend was able to deduce from his tests, the transformer may very well have been shorted out. I think it's safe to say that this little TurboExpress is officially...blind. :( I can use this as a big music player I guess...
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 04, 2011, 08:08:51 AM
do you have it with you? join us in chat sometime
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 05, 2011, 09:49:29 AM
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 05, 2011, 09:54:21 AM
i am usa west coast, others are east coast, asia and other places. you will find knowledgeable people on just about any time you look.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Charlie on September 07, 2011, 11:19:30 AM
Just out of curiosity, why have you narrowed the problem to the transformer? What did you do to prove it is not the circuit that "runs" the transformer?
Charlie
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: chop5 on September 07, 2011, 06:23:07 PM
farankoshan you can send the motherboard and slot only in a small necklace box or something to save on shipping. just pack it good in a static free bag. one of us can assemble it with one of our units and be able to service it. just an idea. :wink:
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 07, 2011, 09:39:28 PM
well said chop. im sure it can be fixed by one of us, i just was trying to save some shipping costs by trying to walk him through it.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 08, 2011, 07:55:13 AM
This is a pretty good idea actually. :) I will weigh my options and study packing methods.
You guys have been really helpful so far, and I appreciate it!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 13, 2011, 07:50:55 AM
He made a rough map of what the transformer looks like (hope this shed some light for a solution to present itself):
PRIMARY SIDE SECONDARY SIDE 1 - live 1 - dead 2 - power supply 2 - dead 3 - live 3 - dead 4 - live 5 - ground
And he assumes that the main power line runs between Primary 2 and Secondary 3. Is this correct?
Does the above make sense to you guys?
Does this guy's video relate to the above?
In the middle of the video, he shows a diagram that seems to look like my problem area. Does this make any sense to you guys? You think that this diagram will help me try again to fix Video on my TGExpress?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 13, 2011, 10:13:59 AM
nope he is showing just the cap fixes
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on September 13, 2011, 04:19:51 PM
Nice how the guy in that video doesn't credit any of the original sources for the fixes.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 13, 2011, 10:41:02 PM
He does for a quick bit, but not the ORIGINAL ones... Oh well...
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: nat on September 14, 2011, 12:58:09 PM
Yeah I heard him mention some guy who I'd never heard of, "Morse One" or something, not that "Morse One" had any part in discovering these fixes either.
Oh, well is right...
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 19, 2011, 05:54:12 PM
I just wanted to reawaken the discussion on a video fix:
This thread does really well explaining capacitor switches to help backlit-but-no-video problems, but what about if both video or backlight are out? :(
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 22, 2011, 05:56:39 PM
Ok, so as I have been posting earlier on this thread, my TurboExpress isn't giving any video, just audio.
So today, I got myself a bright LED torch and shined it onto the screen and it appears there is video actually being generated & there is movement and sprite work on that screen! So it appears that the lamp is the problem. Any suggestions as to how to get this fixed, or specs so I can go to a hardware shop and get a replacement lamp? :)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 22, 2011, 10:56:07 PM
the lamp is powered by the transformer, which you said had no power. at least we now know thats the prob.
i will soon have a spare screen, but i dont think its your issue
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 22, 2011, 11:02:50 PM
the lamp is powered by the transformer, which you said had no power. at least we now know thats the prob.
i will soon have a spare screen, but i dont think its your issue
Hey steve! Thanks for replying.
Well, if I can have a makeshift lamp put to backlight this screen, any chance you know the specs of this lamp and how to replace it? Coz if we can replace the lamp with a new one, and it still doesn't light up, then at least we've proven beyond all doubt that it's a transformer-related issue. Rerouting power from another source is always a viable option if the transformer won't allow current. :) It's good news for me that this LCD still works. :) I just need to know how to fix the backlight. :)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 23, 2011, 07:22:07 AM
im in the process of an LCD transplant (using a 3.5" backup cam display). the last step will be to remove the backlight power, and i will trace it out then gaining a basic schematic of it. once the schematic is done i should be able to help you through the circuit.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 23, 2011, 08:01:13 PM
i may not end up tracing the circuit out. the transformer is driven by transistors Q900 and Q901 normally when backlight circuits fail its the driver transistors.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 23, 2011, 09:21:30 PM
i dont have a color encoder installed yet, but i disabled the stock back-light ballast. years back i tested my power drain on this unit and it was 600mA. tested running the 3.5" display 97mA
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 24, 2011, 05:53:26 PM
So how would I go about using this info? :) Sorry, I got a little lost with the lingo (ballasts, transistors, etc.) What do I ask my local hardware store for?
I wonder if there would be a way to remotely power a lamp to go behind this LCD...
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on September 24, 2011, 06:25:04 PM
the problem likely relates to the transformer not getting pulsed. the transistor info should be useful to your tech guy
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: farankoshan on September 25, 2011, 04:55:20 PM
Ok, will see what we can do. Thanks!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on January 27, 2012, 06:52:04 AM
i have an express here showing jailbars (common for RGB modded systems). the cause is capacitor CC505. tracing to asses relation to a possible fix for duo mods
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on February 06, 2013, 06:36:15 PM
I am working on a PC engine GT for the forum member tangentt right now and I am having screen issues. Already re-capped the thing, checked for bad traces off of the caps, checked the usual Q900 and Q901 transistors, and tested another screen. Basically the screen will not get bright enough. I can see a clear picture if I hold the GT at an extreme angle but if you look straight at it you can barely see anything at all. Maybe there is another bad transistor somewhere? If anyone has any guesses it would be much appreciated.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on February 07, 2013, 05:15:33 AM
id check the -24V supply, as its your drive voltage
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on February 09, 2013, 12:46:15 PM
I checked Pin 3 for the screens ribbon cable and it is supplying 24V.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on February 09, 2013, 01:40:48 PM
it could be the 5V or contrast pin
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on February 10, 2013, 09:58:17 AM
So I went through the pins again for the screen today just to double check things. Turns out I must have not read something correctly yesterday. The 24V pin ends up reading almost 27V when the screen is not plugged in. As soon as the screen is plugged in the voltage drops to 15V. I know that a good working express should stay very close to 24V regardless of having the screen plugged in or not. Does that sound like there is a short somewhere to you?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on February 10, 2013, 05:03:35 PM
that sounds more like an open cap or regulation fault on the 24V line
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: mrchuck999 on April 02, 2013, 04:30:42 AM
Hey guys, You know the blue cap at the back light connector? Has anyone determined the value of this cap ? I know its a long shot but I've tried almost everything else so I would like to replace it. Mrchuck999
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: macphreak4evr on August 02, 2013, 11:28:22 AM
Thank you so much, I did this and the sound fix and I am back in action!!!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: RxM on September 22, 2013, 12:42:15 PM
Hi Samson, i have same issue. When i went to remove the defective cap for video, my trace also lifted. So isit ok to solder the neg lead to the mosfet transistor? Cause i dont see any other trace. Any Help greatly appreciated. I went to do the rest of the cap replacement and now im not getting no sound or video. Screen light up and flicker vertical. I spent countless hours trying to figure out what else could be wrong but i have no clue.
Thanks for the awesome repair guide. I snagged a practically brand new TE off of Ebay for $34 and managed to fix it with a $1 part from Radio Shack.
It got a little hairy there for a bit though. I thought I was being careful but still accidentally pulled the negative trace off the board when I removed the capacitor. Thankfully the trace ripped pulled up far enough for me to follow it to another solder point. The leg of the little transistor/MOSFET that sits just adjacent to the cap will work.
If I had it to do over again I would definitely have tried to touch the soldering iron to the legs and gently pry them up rather than trying to pull the cap off cold.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=363;image) Looks so innocent just sitting there.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=365;image) Disaster strikes! I did not notice the little trace that was ripped out of the surface of the board at first - I honestly thought it was just a strip of paint or glue or something. The scratches you're seeing where the pad for the negative trace was are my desperate attempts to find what the pad had been attached to. I was hoping that if I dug into the board I would find another solder point. I realize at this point that was silly, but at the time I had no idea.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=367;image) But that was exactly what I needed to find an alternate soldering point.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=369;image) Here is the alternate soldering point magnified some more.
I decided to remote-mount the cap because the connections, while solid, were so fragile I didn't want to risk any more bending and twisting than I had to. It may not be pretty but it works like a champ.
Thanks for the awesome repair guide. I snagged a practically brand new TE off of Ebay for $34 and managed to fix it with a $1 part from Radio Shack.
It got a little hairy there for a bit though. I thought I was being careful but still accidentally pulled the negative trace off the board when I removed the capacitor. Thankfully the trace ripped pulled up far enough for me to follow it to another solder point. The leg of the little transistor/MOSFET that sits just adjacent to the cap will work.
If I had it to do over again I would definitely have tried to touch the soldering iron to the legs and gently pry them up rather than trying to pull the cap off cold.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=363;image) Looks so innocent just sitting there.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=365;image) Disaster strikes! I did not notice the little trace that was ripped out of the surface of the board at first - I honestly thought it was just a strip of paint or glue or something. The scratches you're seeing where the pad for the negative trace was are my desperate attempts to find what the pad had been attached to. I was hoping that if I dug into the board I would find another solder point. I realize at this point that was silly, but at the time I had no idea.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=367;image) But that was exactly what I needed to find an alternate soldering point.
(http://www.pcenginefx.com/forums/index.php?action=dlattach;topic=5015.0;attach=369;image) Here is the alternate soldering point magnified some more.
I decided to remote-mount the cap because the connections, while solid, were so fragile I didn't want to risk any more bending and twisting than I had to. It may not be pretty but it works like a champ.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on October 16, 2013, 12:47:59 PM
it was the 5V regulator running at 3V due to a cracked resistor R506
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on January 12, 2014, 07:50:20 PM
Hi, I seem to have the same or similar problem as Keith Courage reported above.
I had previously changed the video cap a few years back - that resolved an initial dim screen issue I had.
Recently I tried the GT and after 10 mins the screen went very dark. Because I also had low sound, I thought I would complete a full recap.
After the full recap I still have the same screen issues:
The backlight is working - although very dim. You have to extremely tilt the unit to see anything - this gets worse within minutes and then backlight shuts off completely.
Any help guys?
Regards, Shaun
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on January 21, 2014, 01:44:02 PM
The backlight will shut off if not used (push a button) Also if unable to adjust brightness properly it is a 24v supply prob if not a bad screen
Sent from my ADR6300 using Tapatalk 2
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on January 21, 2014, 08:27:16 PM
Thanks for the feedback.
IIRC when I measured the voltage on VR500 it was only around 10v. I'm assuming this should be 24v.
Any pointers as to how I can perform further diagnostics and/or fix the supply problem?
(Thanks for the reply to my PM btw) - In the PM you mentioned about a possible arcing. What should I look at to establish if this is taking place?
I've placed an order for replacement Q900 and Q901 transistors, but I'm assuming this will not fix the issue?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on January 22, 2014, 02:28:12 AM
Not sure at the pot You should have -24V at the - pin of the 22uf cap near the pot
Sent from my ADR6300 using Tapatalk 2
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on January 22, 2014, 02:30:33 AM
The pot on the side, not the one @ the top
Sent from my ADR6300 using Tapatalk 2
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on January 22, 2014, 02:32:55 AM
Q900,Q901 supply the backlight transformer and are all or nothing
Sent from my ADR6300 using Tapatalk 2
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on January 22, 2014, 07:17:34 AM
Not sure at the pot You should have -24V at the - pin of the 22uf cap near the pot
Sent from my ADR6300 using Tapatalk 2
11v measured at that point.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on January 24, 2014, 03:45:22 AM
Any pointers on how to resolve this low voltage issue? :)
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on January 25, 2014, 12:55:59 PM
First unplug the screen and recheck (keith had a shorted screen) The video cap fixes all relate to that voltage The pot near the side of the unit adjusts the -24V supply, the one near the top adjusts the +5V
Sent from my ADR6300 using Tapatalk 2
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on January 26, 2014, 03:00:32 AM
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on March 08, 2014, 10:06:21 PM
Thanks for that link..... where are the screens available from?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on March 09, 2014, 05:04:13 AM
If you need an original screen, anyone doing screen swaps should have a pile of good ones
Sent from my ADR6300 using Tapatalk 2
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: fagin on March 09, 2014, 05:13:50 AM
It's not an OE screen I need. Something is obviously mullered with my main board, even after looking at the areas you suggested, I didn't get anywhere.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on March 09, 2014, 07:51:37 AM
screen swaps can be done, with a composite mod
ebay sells screens, some work some dont
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: coryoon on July 09, 2014, 11:42:01 AM
Hi,
I have a GT with the 'screen on but no picture' issue - screen is black (but lit), sound works etc.
Is there anyone in the UK that does the Cap replacement?
Thanks.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Rosser on August 10, 2014, 06:26:23 PM
deleted post
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Moudamir on September 08, 2014, 12:59:06 AM
Hello everyone,
So I follow the replacement process for the capacitors, mine was showing no video and no audio. Video only backlight sometimes shadows !!! And audio was low. I've changed the audio circuit !!! And it's perfect. And I've changed the video one it came back for 10 sec and that's it !!! Don't know what to do !!! I've changed total 10 capacitor out of 18 still nothing. Didn't go under the shield yet... Any ideas ?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on September 08, 2014, 07:31:49 AM
Remove the shield and change the rest before looking at any other options for the problem. That way you can at least rule out the capacitors if the problem still exists.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Moudamir on October 02, 2014, 08:43:18 AM
Hey guys,
I end up changing everything all the caps, now it's worst screen stays greenish, with some shadows if you angle the TE forward.
Kind of lost !!! Any ideas ? Screen is May be dead....
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on October 13, 2014, 08:12:26 PM
Look around for bad traces. If it was better before changing the rest then a trace or pad must have been pulled up.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: speedlolita on March 10, 2015, 06:28:27 AM
Hi! Thought I'd post my issues with a PC Engine GT unit I was asked to re-cap.
After replacing all of the caps most of the issues with the unit were fixed.
However, the brightness dial isn't working as it should. That is, after the unit has been on for maybe 15 seconds. If the unit has been discharged for a while then the dial seems to work as desired. Once it settles down though the dial has little to no effect and the image just gets progressively darker.
The main video cap had leaked when I got there so I scraped away the excess junk and reflowed the transistors in that area but that didn't appear to do anything.
Aside from attempting to re-cap the video capcitors again I'm at a loss. Has anyone else experienced similar symptoms?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on March 13, 2015, 06:09:57 PM
its a power hog battery fade will cause this
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: KingDrool on December 28, 2015, 06:42:29 AM
My son just used these instructions as part of a job-shadow project. It worked brilliantly! Thanks for the handy guide. You made it so simple even an 8 year-old could do it!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: bovined on May 17, 2016, 08:01:43 AM
I had a perfectly workinh TE but I picked it up the other day to play some Blazing Lazers and it would only power up the screen going from white then quickly to black with no audio. I tried moving the hucard a bit and it will sometimes power up to a green or orange screen and then quickly to black again. The brightness dial still works but thats it. I tried replacing the cap in question from this thread but it seems to be be behaving the exact same way afterwards. Any ideas on what is causing this issue or what the next best caps to try replacing would be?
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on May 17, 2016, 08:30:02 PM
going black after white tho i havent seen it on a TE/GT, i have seen on other versions it means the system crashed shortly after resetting the pallet registers the cause has been bad 6280/ bad work ram/ bad trace any one can cause this, and it could be all, but most common is bad traces
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: bovined on July 25, 2016, 11:15:20 AM
Just want to say big thanks to thesteve for fixing my TE! Awesome fast service and communication. A true pro!
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: RetroWeirdo on July 25, 2016, 05:51:24 PM
Hey y'all, I just did a recap on a TurboExpress which had stopped working (This was my 2nd time repairing one of these, 1st one came out great). This time around went a little different. When I was trying to carefully remove the portions of white glob that were covering the solder pads of the caps in the corner, there was a large piece that broke off and took a piece of the black plastic top off the copper coil pack hidden under that white goop. So I assumed this goop was acting as a insulator for the coil/glue for the 100uf 16v caps that it runs into. I attempted to use hot glue to repair this and continued the recap job.
Once I reassembled and tested the unit, I found the screen to flicker and get distorted with pixels in improper places. After double checking all of the solder points and some other trouble shooting without the back half of the shell, I was able to get the distortion to stop but the light flicker continues to occur as if possibly a slight issue with the backlight. But I wonder if this is possibly related to that coil from under the white goop. Could this occur if it is damaged or not adequately insulated?
Thanks
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on July 26, 2016, 08:08:41 PM
Insulation of that part shouldn't effect anything. I've never seen flickering like you described. Maybe you should post some pics of the graphics issues? Could be bad ram/or damaged trace related.
Also, in the past I've accidentally uncovered the part you speak of before and have even broken off a leg/contact point before. I've always just re-soldered the wire back to where it originally went without any ill effects. Then cover up with hot glue or epoxy. So hopefully neither of the two contact points for the coil have snapped off anywhere.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: XLR-VIII on July 28, 2016, 07:17:38 PM
Hey guys can someone help me with this.... I replaced all 18 capacitors on my TE. End result is no video....backlight works and I have sound! Anyone got any ideas?
I attached a link to a video of my TE
https://youtu.be/3BwF37SjdpM
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on July 28, 2016, 07:56:51 PM
Looks like something isn't getting the correct voltage. Make sure there are not any broken traces to any of the caps you installed.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: RetroWeirdo on July 29, 2016, 01:59:23 PM
Insulation of that part shouldn't effect anything. I've never seen flickering like you described. Maybe you should post some pics of the graphics issues? Could be bad ram/or damaged trace related.
Also, in the past I've accidentally uncovered the part you speak of before and have even broken off a leg/contact point before. I've always just re-soldered the wire back to where it originally went without any ill effects. Then cover up with hot glue or epoxy. So hopefully neither of the two contact points for the coil have snapped off anywhere.
Thanks for the advice KC. I tried some additional trouble shooting (different caps, reflow on solder pads) with no change. I posted a couple private videos to YouTube showing the pulsing flicker issue, here are the links: Video 1: https://www.youtube.com/watch?v=MevovLPARy0&feature=em-upload_owner#action=share Video 2: https://www.youtube.com/watch?v=g9rXBf_rj4E&feature=em-upload_owner#action=share
If you look carefully in the first video you can also notice that there is a temporary burn-in on the screen that carries over from whatever is displayed previously, so in the video you can see the Keith Courage title screen still faintly showing on the screen once the game starts.
I rechecked the traces as well and couldn't find any issues, though it seems like that could possibly be causing the issue, or maybe the ribbon cable from the hu-card reader to the main board? What do think from the videos?
Thanks
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Keith Courage on July 29, 2016, 08:43:39 PM
I've seen something similar happen when the 1 10uf cap pads get ruined but not exactly the same. Also, are you by chance using a generic ac adapter? Does the same thing happen on batteries? I wonder if this is the sign of an actual bad screen.
The burn in on the screen is completely normal.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: XLR-VIII on July 29, 2016, 09:29:40 PM
Looks like something isn't getting the correct voltage. Make sure there are not any broken traces to any of the caps you installed.
I'm getting 7.8v from an AC adapter. When unit powers on it drops to 3.8v Checked some the caps, most read about 3.5-3.7v Measured on pin 3 of the display ribbon cable only get -2.5v
Anything else I should check and where does the 24v start ?
Thanks
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: RetroWeirdo on July 30, 2016, 04:50:08 AM
I've seen something similar happen when the 1 10uf cap pads get ruined but not exactly the same. Also, are you by chance using a generic ac adapter? Does the same thing happen on batteries? I wonder if this is the sign of an actual bad screen.
The burn in on the screen is completely normal.
I will recheck the 10uf again. No I first tried this unit reassembled on batteries and noticed the problem, since then I have been trouble shooting it partially disassembled with power from a 1st party NEC TE AC adapter. That would kinda suck if the screen has a legit problem, Though it might be nice to upgrade to a newer LCD.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: thesteve on August 14, 2016, 10:02:30 AM
Looks like something isn't getting the correct voltage. Make sure there are not any broken traces to any of the caps you installed.
I'm getting 7.8v from an AC adapter. When unit powers on it drops to 3.8v Checked some the caps, most read about 3.5-3.7v Measured on pin 3 of the display ribbon cable only get -2.5v
Anything else I should check and where does the 24v start ?
Thanks
if your supply is dropping below 6V it wont work
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: hard_gb on November 19, 2022, 09:04:33 AM
Please, the images in the post are gone. I need them to make the modification. Thank you :adol:
It's long been known that by replacing all the capacitors in the audio circuit on the Express PCB you are able to cure all sound issues, but video issues have been a bit of a grey area. What has been unknown (until now) is just which component is directly linked to the common video problem these units are beginning to have. Let's give a round of applause to Sinistron, the real hero in all this, for donating a TurboExpress with bad video for me to butcher on the operating table. It was a very long and tedious process, as I ended up replacing almost everything on the board by the time I was done and I had to play test after every component which meant quite a bit of assembly and disassembly. The culprit turned out to be the smallest, most innocuous capacitor on the entire board and the only reason it wasn't the very last one I did was because there was one cap I didn't have a proper uF/voltage match for. At the very least all this paid off and finally put to rest just what causes the no video issue. Real quick: the capacitor in question is in the power circuit, specifically, the line that supplies the mains to the LCD. This cap fails, dries out, bleeds, etc causing insufficient voltage supplied to run the LCD.
So let's get down to it.... I took photos documenting the entire process, but I'll only post the relevant ones here.
(http://pic.photobucket.com/bwe.png) Circled in green is the audio circuit. We already know what these caps are for, so we ignored them for this procedure. Circled in red is the culprit for the video issue. You can barely see it, can't you?
(http://pic.photobucket.com/bwe.png) Since I didn't know where the problem was specifically, I removed the shield covering the CPU, VDC, etc. The caps circled in blue are the ones that are exposed by removing the shield. It is not necessary to replace these to fix the video, but Sinistron got a freebie on this one. I included this pic so folks who might want to replace EVERYTHING can see just what's under the shield.
(http://pic.photobucket.com/bwe.png) Circled in red is the replacement cap I installed in place of the bad on. The cap is a 4.7uF 35-volt electrolytic. This is THE culprit of the backlight-but-no-picture video issue. Replace it and your video works again.
(http://pic.photobucket.com/bwe.png) Just a final look at the board after I was done with it. I had to run wires to remote-mount a few of the replacement caps due to not enough room on the board, etc. FYI, there is plenty of open space down behind where the batteries sit where you can remote-mount caps if you need to.
There you have it. It's a simple fix, really, and luckily it's probably the most easily accessible cap on the entire board.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: MasterofBiscuits on November 20, 2022, 06:09:02 PM
I believe the cap being referred to below is CC501 which is at the top of the board. This info is outdated though, you need to replace all the caps as they will leak and corrode the PCB.
It's long been known that by replacing all the capacitors in the audio circuit on the Express PCB you are able to cure all sound issues, but video issues have been a bit of a grey area. What has been unknown (until now) is just which component is directly linked to the common video problem these units are beginning to have. Let's give a round of applause to Sinistron, the real hero in all this, for donating a TurboExpress with bad video for me to butcher on the operating table. It was a very long and tedious process, as I ended up replacing almost everything on the board by the time I was done and I had to play test after every component which meant quite a bit of assembly and disassembly. The culprit turned out to be the smallest, most innocuous capacitor on the entire board and the only reason it wasn't the very last one I did was because there was one cap I didn't have a proper uF/voltage match for. At the very least all this paid off and finally put to rest just what causes the no video issue. Real quick: the capacitor in question is in the power circuit, specifically, the line that supplies the mains to the LCD. This cap fails, dries out, bleeds, etc causing insufficient voltage supplied to run the LCD.
So let's get down to it.... I took photos documenting the entire process, but I'll only post the relevant ones here.
(http://pic.photobucket.com/bwe.png) Circled in green is the audio circuit. We already know what these caps are for, so we ignored them for this procedure. Circled in red is the culprit for the video issue. You can barely see it, can't you?
(http://pic.photobucket.com/bwe.png) Since I didn't know where the problem was specifically, I removed the shield covering the CPU, VDC, etc. The caps circled in blue are the ones that are exposed by removing the shield. It is not necessary to replace these to fix the video, but Sinistron got a freebie on this one. I included this pic so folks who might want to replace EVERYTHING can see just what's under the shield.
(http://pic.photobucket.com/bwe.png) Circled in red is the replacement cap I installed in place of the bad on. The cap is a 4.7uF 35-volt electrolytic. This is THE culprit of the backlight-but-no-picture video issue. Replace it and your video works again.
(http://pic.photobucket.com/bwe.png) Just a final look at the board after I was done with it. I had to run wires to remote-mount a few of the replacement caps due to not enough room on the board, etc. FYI, there is plenty of open space down behind where the batteries sit where you can remote-mount caps if you need to.
There you have it. It's a simple fix, really, and luckily it's probably the most easily accessible cap on the entire board.
Title: Re: REPAIR GUIDE - TurboExpress/PC Engine GT: Video Fix
Post by: Cassius on April 16, 2023, 06:31:38 AM
Hi, I’m currently working on a Pc engine gt that I find in my spare parts drawer, the voltages were all over the place and it had suffered heavy cap leakage, a recap hadn’t moved me any father until I noticed that d502 was missing off the board as 2 out of its 3 pads were dissolved, I’ve ordered the 1ss184 as recommended and I think I’ve identified the points where I can bypass it but can anyone confirm where the points are ? Thanks in advance.