Author Topic: need PC engine GT Q500 transistor replacement part??  (Read 1102 times)

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #15 on: March 16, 2020, 11:11:17 AM »
Well, the s-video would be if you plan to also hook the express up to a TV. I have yet to find a good screen for the express that will take a S-video signal so no reason to go that route unless you plan to use it with a TV that can use s-video. These 3.5mm screens from console 5 are excellent for composite video. They are what I use now. https://console5.com/store/universal-3-5-composite-video-lcd-module-320x240.html
Console 5 also sells the new larger size screen protectors. https://console5.com/store/turboexpress-3-5-glass-lens-screen-cover-for-lcd-swaps-turbo-express.html but they can be bought for less here https://www.ebay.com/itm/Turbo-Express-3-5-lcd-Glass-screen-protector-NEC-pc-engine/233246430957?hash=item364e9216ed:g:rfQAAOSwbzpc9WUO

Hi Keith  I ordered the composite board for GT and wired like on this picture but nothing when I put the composite video cable on my tv... 
Where can you take the 10 v for the new screen? Directly on the power jack socket?
Thanks

Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #16 on: March 18, 2020, 01:40:52 AM »
If you are not getting anything on your TV then something isn't right. You should be able to use a typical RCA plug on your TV.
I wonder if your ground is good. I always run my ground wire to one of the points where the grounding shield connects to the board.



For a replacement screen you can tap power from the power switch itself.
« Last Edit: March 18, 2020, 01:42:24 AM by Keith Courage »

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #17 on: March 18, 2020, 02:05:53 PM »
If you are not getting anything on your TV then something isn't right. You should be able to use a typical RCA plug on your TV.
I wonder if your ground is good. I always run my ground wire to one of the points where the grounding shield connects to the board.



For a replacement screen you can tap power from the power switch itself.

thanks Keith
 I checked for my groud and it is a real ground so no issue with that. And I used RCA cable (that works with my nomad)
So I think my last chance to make it alive is dead  :cry:
there  is no improvement, still just sound but no display.


Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #18 on: March 18, 2020, 03:33:35 PM »
I've never come across a system that has had no video output what's so ever while still putting out audio.. Even if the 6260 video chip is faulty, you generally get a glitchy image of some sort.

Try reflowing solder over your pins on the video board that you installed again. Also, give the second video output on the board a try just in case that first transistor is faulty.

Also double check that there's 5 volts on that power wire you've run.

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #19 on: March 18, 2020, 05:27:34 PM »
i have double checked:
 solder are ok
I have 4,78V for the 5V so i assume it's ok
and I test the second video ooutput on the board and same issue.

I tried a bit longer  (with bomberman 94) and during all the beginning , on this game there is a "presentation video" and after this presentation you have the title screen. I realized that I have a bad display on my TV (just for the title screen, if I wait a bit longger the presentation video restart and so black screen on my tv.
here a video of the display issue:
https://www.dropbox.com/s/05n595ngt4cakuf/20200318_215408.mp4?dl=0

Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #20 on: March 18, 2020, 11:29:41 PM »
I've never seen that before. Looks like a sync or grounding issue.

Also, dumb question. That isn't a Pal signal TV is it?

Also, why does the solder look all weird, wrinkly, and lumpy on some of the new caps you installed? The negative pad looks really bad on the cap you pulled 5V from and so does the positive connection for CC703. Might want to check the solder for the new caps again.
« Last Edit: March 19, 2020, 07:45:38 AM by Keith Courage »

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #21 on: March 19, 2020, 08:09:09 AM »
The picture I posted is one I took here :https://www.pcenginefans.com/forum/index.php?topic=22810.0

Mine are there ;)
https://i.postimg.cc/3JL80MLH/20200319-081843.jpg
https://i.postimg.cc/XYzYmMFg/20200319-081851.jpg
https://i.postimg.cc/PqCP5fhc/20200319-082007.jpg
https://i.postimg.cc/ZYGsCP0J/20200319-102659.jpg

So I don't think I have bad solder...
I set the 5V at really 5V as you said and remove the 2 4,7F caps: same issue.

and my screen is ok I thnink beacause I can see my sega nomad display with the same rca cable


bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #22 on: March 19, 2020, 10:34:30 AM »
My mistake!! :-[
the pin 39 and 40 were shorted!
Now it works!
thanks Keith for your time ;)

Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #23 on: March 19, 2020, 03:44:57 PM »
Yay! Another system Resurrected. :dance:

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #24 on: March 20, 2020, 01:59:58 PM »
Keith
I still have one GT with sound issue (the sound is really weak).
al capacitors have been changed, I also tried another controller board with another speaker (which works great on another GT) and same issue.
I tried to switch sound amp too and potentiometer but nothing change.
Do you know if I can find somewhere a GT schematics (at least sound part)?
thanks

Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #25 on: March 23, 2020, 05:01:58 AM »
Weak out of both headphones and speaker or just the speaker?

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #26 on: March 23, 2020, 12:53:52 PM »
Weak out of both headphones and speaker or just the speaker?

no just weak with speaker, it normal and good with headphone

Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #27 on: March 24, 2020, 12:39:08 AM »
Did you try another headphone jack?  There is a switching portion of the headphone jack that tells the system whether to use the external speaker or not.
« Last Edit: March 24, 2020, 01:27:28 AM by Keith Courage »

bdoi

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #28 on: March 24, 2020, 04:02:57 AM »
Did you try another headphone jack?  There is a switching portion of the headphone jack that tells the system whether to use the external speaker or not.

Yep, I tried to switch head phone jack and same issue. That's why I asked if some schematics exist at least for sound part?

Keith Courage

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Re: need PC engine GT Q500 transistor replacement part??
« Reply #29 on: March 24, 2020, 06:01:05 AM »
Not sure if they exist. I don't have any.

Besides a different speaker, did you also try another controller board? Could be a bad lead in the white ribbon cable for the controller board.
« Last Edit: March 24, 2020, 06:03:01 AM by Keith Courage »