PC Engine GT Screen Fix ?

[chaoticjelly]

Hey guys,

I have done the GT sound fix, and im just wondering if anyone has cracked the screen fix yet?

The GT I am trying to fix, the backlight works fine, if I switch the screen with a working unit, the screen works, if I try a working screen from another unit on the one with the screen that doesn't work, it doesn't work.

So in short, theres something on the mainboard of the GT which is making the picture not appear..

I did quite a bit of searching on the forum and the 'net, and didn't come up with much.

I found a post by "gamedoctorhk" here: http://www.pcenginefx.com/forums/index.php?topic=1701.msg16768#msg16768

Where he says that its simple to fix the screen, you need to replace a part, but he doesn't say which part. I looked at his other posts and it says he is gamedoctorhk on ebay, I messaged him and he tells me that he doesn't know which part. So I direct him to this post and he says its not him, which is weird since he advertises the same items here, has the same email address posted here, and the same username, so I think he's unwilling to tell me which part to replace which is disappointing..

I'm guessing it's a capacitor but I was just wondering if anyone knows which one in particular?

Oh, and the GT I need to fix, appears to have a sound fix already done on it, but instead of the capacitors being replaced for the sound, it seems that the speaker wires have been disconnected from the board with the controls on, one wire has been soldered to the metal shield that covers some of the circuitry on the mainboard, and the other wire has been soldered directly to the leg of a chip which just pokes out from under the metal shield, so I suppose this is a fix with no surface mount capacitor removal / replacement necessary? which is nice.. I can post a couple of pics up if anyone is interested?

Anyway thanks in advance, hopefully can figure out which cap to replace and get this GT screen issue sorted 

[D-Lite]

I found all the same things as you and just never got around to figuring out exactly what the issue was.  Seems to be a capacitor too, but I just haven't had the time/patience to search that one out.

Anyone?

[Keranu]

Oh, and the GT I need to fix, appears to have a sound fix already done on it, but instead of the capacitors being replaced for the sound, it seems that the speaker wires have been disconnected from the board with the controls on, one wire has been soldered to the metal shield that covers some of the circuitry on the mainboard, and the other wire has been soldered directly to the leg of a chip which just pokes out from under the metal shield, so I suppose this is a fix with no surface mount capacitor removal / replacement necessary? which is nice.. I can post a couple of pics up if anyone is interested?

Hey if that's an easier/safer way to fix the sound, I'd be interested in some pics and info so I can try it myself since my sound needs fixed!

[chaoticjelly]

Hey Keranu,

Here's a pic with regards to the easy soundfix.

What you need to do is desolder the black and white wires from the speaker.
Unplug the connector they go to.

Solder two new wires on, of a longer length, make them fairly long, you can always reduce their length later.

The wire you now have soldered to where the black wire was, solders somewhere to ground (in the case of this PCE GT, it was soldered to the metal shield, its the black arrow and circle in the picture.

The wire you now have soldered to where the white wire was, solders to the leg of the chip which is just poking out from under the metal shield, its the white arrow and circle in the picture.

And thats it. Obviously its probably only a fix for the speaker, not the headphones too. And replacing the original caps is probably still the best way to fix, but this seems to be an easy fix for the less nimble  sorry about the poor pic, if you need any clarification just ask me.

I think im also quite close to fixing the SCREEN issue!

[Keranu]

Thanks a lot for responding and posting a pic! Unfortunately since you said it won't fix the headphone sound, I'll probably just replace the cap sometime.

[nat]

My headphone jack works but the speaker doesn't. And this is after already replacing the cap.

I wonder if I did the mod this guy is showing if I'd get sound from the speaker now, too?

[chaoticjelly]

I've solved the issue now. PC Engine GT with an apparent "faulty" screen, is now working like a charm (and with loud sound and all!).

Firstly I tested the screen in another fully working GT, the screen worked great - tells me the issue is something other than the screen, i.e. component(s) on the GT's main PCB.

I checked the voltages going to the screen with my multimeter, and compared those to the voltages going to the screen with the GT that was fully working - interesting, I noticed one MAJOR variation in voltage - perhaps the lower voltage was not enough to drive screen output?

I tried to follow the trace, but it proved quite difficult and I lost it.

So then I started looking at the capacitors, thinking a lower voltage was probably a dodgy capacitor. I noticed that on all of the capacitors, where the silver legs are, they were not silver/metal coloured but in fact yellow/brown/dull. I removed one capacitor to look underneath. A brown mess of dried electrolyte!

Every surface mount capacitor on the PCE GT PCB had leaked!

So I went and ordered replacements, getting surface mount where possible, and a couple of strange values/max voltages were replaced with microminiature radial electrolytics.

After reassembling everything the unit now has perfect, loud sound, and a great display (bar one dead pixel!)

So I think the general rule now is, that if you have either of the sound/screen problems, replace all surface mount capacitors (except for the three, large, yellow nichion 16v 100uF capacitors, as I removed one of those and it was nice and wet inside!) all of the smaller surface mounts were BAD!

Even my GT that is working perfectly, has this yellow/brown/dull look to the leads, which suggests the capacitors in that unit have all leaked too!

So glad I managed to solve the problem 

[D-Lite]

AWESOME.
Now you need to post pics of which cap it was for the screen.  I couldn't figure it out in the past and it's great news that you did now!  I have a couple of dead units I can do this on.

Thanks!

[chaoticjelly]

Hey D-Lite

I don't know which specific cap, I just replaced them all, there's really not that many, and pretty much all of them were in various stages of leaking, replace them all and it should work 100%