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NEC TG-16/TE/TurboDuo => TG/PCE Repair/Mod Discussion => Topic started by: Dr Honda on September 20, 2020, 07:08:59 AM
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Hi Guys,
Since COVID, I've been working on some system for the local used game store, and I have a problemed TE on the bench. The story with it is.... it was already recaped, and it worked for months. Then, all the sudden, the sound got strange, and the screen went black.
First thing I did was simply put fresh batteries in it, and verify the HuCard would work in another system. I also put it on a power supply.
As I picked around the board... I checked the fuse (it's good) and cleaned up a few caps that looked questionable. I also looked for shorts across caps. (most of the replacement caps are surface mount) So... while it's not great work... all the caps are OK.
After reading a few things here... I checked for 5v... and sure enough... NOTHING. I can follow the supply voltage to the B1182... but nothing out. On Console5 it says it's a "Simple Zener adjustable regulator"... and on a thread here there is a comment saying to "Check the regulator". But... what IC is the actual regulator for the 5v side? (I'm assuming the B1182 is for the back light) This would be so much easier with a schematic, because the mask on this thing is crazy thick. LOL.
Oh... last thing. Since there was a comment about "There should be 5v on almost every cap"... and I could see what caps were on the 5v buss on the TG16 schematic... I fed 5v directly to a cap that I verified was on the buss... and I got sound from the game. (So the chipset is OK) But no picture.
Anyway... any guidance with this would be very appreciated.
****EDIT*****
I just wanted to add... when I put power on the board... nothing gets warm, and I cant find anything that looks burnt.
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B1182 is the DC-DC regulator and you should have 5v on the collector, this is controlled with VR501 and ZD501 is the zener diode. Try injecting 5v to the large pad and see if you get any life. Perhaps one of those components has failed (probably the zener).
The backlight is powered via a transformer which sits under the large cubic shield.
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Thanks for the info !!! Once I get down into my shop... I will put power on the C of the b1182. I will also lift ZD501 off the board to check it.
Thanks again.
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Ok... I put 5v on the big tab of the B1182, and I get nothing. So, I lifted it off the board, and I still get nothing with 5v soldered to the pad on the board. For giggles, I lifted ZD501 off the board, and it seems to be OK. I get 0.6xx V, and 2.8xx V in diode mode. And I get a few Meg Ohms one direction, and OL the other. Just for verification... I checked a new Zener I have for an Atari Lynx (also 6 AA batteries, and needs 5v) It gives me more or less the same readings.
Since that didn't bring happiness... I decided to check all the caps for a short. I found that C900 is shorted. (small ceramic) So I took it off the board, and it was ok. The 2 pads show continuity. But, it looks like it's connected to the transformer for the backlight. Incidentally, I do have a backlight. (Just a black screen)
So, anyone have any other thoughts?
Thanks
****EDIT*****
From the pad of the B1182 to any of the 5v pins on the chips, and Caps, I have 4K ohms. Seems like a lot of resistance if that's the output for the 5v side of things. And, it seems strange since there isn't anything between the regulator and those pins on the TG16. Does anyone have a schematic for this thing?
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You say you have a backlight and no picture, can you describe how the screen looks? Does it have a greenish tinge like this?
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@masterofbiscuits
yep, just like that with either batteries, or power supply. Back light on... pixels are dark. And, if I put 5v on a cap tied to the chips... game boots with sound... but still no pic. 5v on the tab of B1182 gives nothing.
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If it looks like that, the backlight is not on. This is what it looks like when the backlight is not working - I had exactly this problem myself and thought the same thing. But actually that glow from the screen is the LCD itself.
It sounds like there may have been a failure on the backlight circuit somewhere. Personally I would remove, clean pads and replace all the capacitors just to be certain that those are not the problem. If no change, replace Q900 and Q901 as these can sometimes fail and are used for the backlight.
I never actually managed to fix mine, though I did get it working by putting in a 3.5" LCD mod.
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@masterofbiscuits
Thanks for the info. I guess I made the assumption that the glow was from the backlight. (I've spent too much time working on old Nintendo handhelds)
Interesting on the screen mod. The person who gave it to me to look at was asking about doing the screen mod, but I told him that I want to get it up and running before the money was spent to do the mod. So, when you disconnected the screen from the system... did the 5v come back to the rest of the board? I guess I should open that solder jumper to "Turn off" the backlight and see what I get. Or... was there something else I should look at to remove the backlight power?
Again... thanks a bunch.
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Mine was a little different as I did still have sound when the backlight wasn't working, so I think you are right to try and get that working before doing the mod. Removing the BLH solder jumper is definitely worth a try, just in case there is something in that circuit shorting the whole thing out.
I would also try recapping it, just to rule it out as the problem. Unfortunately there is no schematic for this as far as I know which makes fixing things such as this very difficult!
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Thanks again.
I pulled Q900 and Q901 off the board, and they check fine. BUT... I found that R512? (maybe R517 have to go back down to the shop) is showing a short. I lifted it off the board and it's showing 33 ohms and the pads are shorted SO... I'm guessing that there is a transistor somewhere burnt up.
Also... I'm getting voltage on the pin going to the battery when there is a supply plugged in. I would think there is a diode that would block that. SO... since that resistor is showing a short... I'm guessing there is an issue in that section of the board.
Any other thoughts or input would be appreciated.
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Another transistor to check is Q500 in the top corner - this is also part of the backlight circuit and has been known to blow and cause backlight failure. Not sure what else to suggest :-k
Oh by the way, I found the best way of looking at the traces was to shine a light through the back of the board, it really helps when you're trying to follow them. It's also easy to see which are front and which are on the back.
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Thanks for all the input so far.
I was kind of suspecting Q500 and the diode close to it on the back side. (under the gray stuff) That's where I found the resistor showing a short. But, before I got a chance to take it off the board... I had to step away from it. LOL. If this was my person unit... I would sit and lift ever single part off the board until I found it. But this is for someone else... and it has someone else's prior work... and it just makes it that much harder to want to sit with it.
Do we know the replacement for Q500? Q900 and Q901 I found at console5.
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Q500: https://www.aliexpress.com/item/32726193004.html
I know what you mean, there is a point where it's just not worth the time. Always good to take a break anyway, sometimes having fresh eyes on it makes all the difference.
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OK... lifted Q500 off the board, and it checks ok with a meter in diode mode. BUT... I got that nasty fish smell when I heated it up. It was good to clean under it at least.
The light trick was a big help. I cant see everything... but things started to align in my head. I could now see what groups of parts, and though holes I needed to look at. AND, it shed some light on R517. It shows a short because it's on both legs of one of the small coils.
On the power input side... under the gray stuff is D500. Do we know what that is? (Kind of diode) I can see a diode on one leg... but not the other. (in either direction) I'm starting to suspect that is keeping power from my 5v side. (The traces are all hard to see there)
And in the 5v power section... I have 2 questions...
1) Do we know what Q503 is? I can see the Zener, and the input power are on it. (bottom 3 legs) but the top 2 legs don't seem to be connected internal. (Checked it in diode mode)
2) I get continuity on the tab of the B1182 to TP501. BUT, to any of the "5v Buss".... I'm showing 4K resistance. Is this what you get on a good running Turbo Express? It doesn't make sense, since the TG16 is clean from the regulator to the 5v side of the chipset.
Again... thanks for all the input.
Oh... and if this was a gameboy, or 3DS... I would have told the customer it's not worth the time to do board level repairs. But these things have gotten crazy expensive... and now it's personal. LOL. No mater how much time I put into it... I'll probably only charge the guy $40. I see this as a good learning experience. Besides... the owner isn't in a rush. He has another one.
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I'm guessing that leaking electrolyte has shorted something out, which is exactly what happened to mine. Every GT I recap now gets a good scrub with IPA and then PCB cleaner sprayed all over it.
Afraid I have no idea what Q503 is or does. I have a stock GT here that I am about to work on, if you want me to test some points with a multimeter let me know and I will go over them when I have it cracked open.
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YES PLEASE !! Thank you. Just check it in diode mode to see if there is a voltage drop between pins. Or, any other method you can think of. Oh... and could you tell me if there is any resistance between the tab on the B1182 and any of the 5v pins on the chips? (i'm getting around 4K)
As an FYI... since I can get the game to boot, and I get sound when I put 5v directly to the chip set (but not when I put it on the tab of the B1182) I told the owner that the only way I may be able to save it is if I put a stand alone 5v regulator in it, and do a screen mod. I know it sounds a little hack... but with this thing... there are just so many unknowns (like what Q503 is) that it may be the faster way to bring it to life.
Thanks again for the help
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Yes, you are correct that doing the Composite video mod+new screen would work. I've done this quite a few times for Express systems that have no image after a cap change.
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Afraid I have no idea what Q503 is or does. I have a stock GT here that I am about to work on, if you want me to test some points with a multimeter let me know and I will go over them when I have it cracked open.
Did you have time to check out Q503? I've gotten most of the parts I need to convert the TE on my bench... but would still like to give it one more shot on getting it running in stock condition.
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Afraid I have no idea what Q503 is or does. I have a stock GT here that I am about to work on, if you want me to test some points with a multimeter let me know and I will go over them when I have it cracked open.
Did you have time to check out Q503? I've gotten most of the parts I need to convert the TE on my bench... but would still like to give it one more shot on getting it running in stock condition.
I did, only just this weekend. I didn't want to remove it so I tested in circuit, hopefully it's useful for comparison.
With anode on A and cathode on all other pins, it just gave me a fixed voltage with no drop.
With anode on B and cathode on other pins it gave me an open loop.
With anode on E I got a voltage drop on D and C but not on A or B.
Just seems to be a regular transistor.
I forgot to test the 5v line ](*,) sorry.
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Thanks for the info. I will check that out tomorrow.
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OK.... I'm getting the same thing. Guess it's ok. UGH.... LOL.
Well... I'm trying to get a few other things done... so I'll probably work on the mod toward the end of the week. I'll post up with the outcome. Thanks again for all the help.
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I just refurbbed a GT today that still had a very faint screen image even after all the caps had been replaced. I could see the game playing but barely - it seemed like the backlight was not at full power. I recapped it again and there was no change, so I replaced Q500, Q900 and Q901 and that fixed the problem. When I removed Q500 I got the fishy electrolyte smell, so I'm pretty sure that was the culprit. I was surprised about this as I'd cleaned the board twice with IPA and PCB cleaner . Keith has warned me about this previously and he was right!
In future I may remove this transistor and clean underneath as part of the recap process.
So if you haven't already, I would remove it and check (maybe replace it).
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@masterofbiscuits
Thanks for the heads up on that. Yes. I did lift Q500, Q900 and Q901 off the board. And you were right. Q500 was "Fishy" when I removed it. I checked it off line, and it seemed ok. If this was my personal TE... I would just start replacing everything. But it still doesn't answer why I don't have 5v... and why there is high resistance between the pad on B1182 and any of the "5v rail" connections. I wish this would have been one of those times where a component would get hot so I could find it. But nothing is even warm with power on it. I've checked all the caps again... I've checked the Zener... and I've checked a bunch of the transistors.
I talked with the owner last week, and he's ok with my idea of installing an external 5v regulator, and doing the LCD conversion. At this point I think it's the fastest way to recovery. And, ironically enough... I'm starting on it today. I just built the consol5 video board, and stopped for lunch. I'm going to head back down in a little while, and I'll put it on the main board, and see if I get anything. I'll let you guys know what happens.
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If you're doing a 5v mod, might as well put a lithium battery in there. I posted a guide on here not long ago, and I updated it the other day to make it a bit simpler. Doesn't require any case cutting, unless you want to add an LED and is fully reversible.
https://www.pcenginefans.com/forum/index.php?topic=23504.0
Definitely worth doing!
(https://i.imgur.com/TFkqeT5.jpg)
(https://i.imgur.com/ep9vlLp.jpg)
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@masterofbiscuts
I saw your Lipo post when I was trying to find some answers on this TE. I'm actually considering it with my own TE. The only reason I haven't done anything like that yet is because mine is in good shape, and I would hate to cut it up. If the prices weren't so crazy on these things... I would find a beater to convert.
OK... for an update... This TE is alive again !! I spent so much time trying to figure out why I didn't have power... I almost feel silly now that I just didn't move forward with this conversion early on. But then again... since this is someone else's money... I had to make sure. But if I get another one like this... I will know, and I will just tell the owner that it's the only way to get it back.
So... I lifted Q500, B1182, the Zener off the board, and opened the bridge for the back light. Then I added a 5v regulator. It gets switched power from the input of where the B1182 was, and feeds the 5v rail directly at one of the memory chips. I have it adjusted to 4.95v at 9.5v input (fresh batteries) and it will output 4.7v all the way down to 5v in. (Set with a bench power supply) I then added the component board from Consol5.... and now she's working just fine. I let it run for an hour on the bench, and nothing was even warm. Today, I have a bunch of things I need to catch up on... but I'm hoping to mod the shell to fit the screen, and have it all buttoned up.
Thanks for all the help guys.
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Hi All,
Thanks again for the help on this.
I'm not sure what the rules are... but the local used game store, who has me fixing stuff... talked me into video'ing some of the things that I find. So, I documented this repair. It turned into a 3 part video... but part 3 gives a good summery, and shows the screen mod. Here's the link if anyone is interested in what I did. I officially started the channel 2 weeks ago, and would love the support of the Turbografx crowd. Oh... also ANY feedback would be appreciated.
https://youtu.be/-1d_ldl_fWs (https://youtu.be/-1d_ldl_fWs)
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You're a natural in front of the camera Tony, I have dropped you a sub :thumbsup:
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Thanks for the kind words. I'm glad you say that I seem like a natural in front of the camera.... because I don't feel that way. But even the guy who talked me into starting this (The owner of Warpzone in Greensburg PA) said I'm being overly critical of myself. He gave me some lights, and some of the props in the "Studio". (Like the Nintendo repair sign and big gameboy picture in the intro) After setting things up... I spent 4 days moving lights around, and trying different things to get rid of shadows. Then he said... "Bounce the lights of the celling." I did that... and everything looked so much better. I also found a $17 lapel mic. It made the sound SO MUCH better. My first attempt was echo-y... and there was shadows, and glair.... and I didn't even post it because I felt it was so bad.
Thanks again for the kind words, and the sub !!