PC Engine GT - no video or sound before and after cap replacement

[Stupid Dufus]

I first received the GT back around 2005 a friend. It powered on fine, but the audio was suuuuper quiet. I put it back in a closet and forgot about it. Fast forward to 2016 and I've started to do some soldering.

I replaced the caps on a PCE Duo without much issue, so I thought I'd be able to do that on the GT.

I turned on the GT to test, and there was no video or sound. The screen would power up, but a black image.

I opened it up, removed all the caps... and then didn't realize how tight of a space there was to work in. I knew I wouldn't be able to install all the new ones myself, so I sent it off to someone to have them install the caps.

I got an e-mail saying caps were installed, but there was still no video or sound. It was mailed back to me.

Any suggestions what it could be? Is this fixable or do I just have a decoration piece?

[SignOfZeta]

Photos (of quality) would be helpful. I'd wager something got borked during the decade you let the caps drizzle their filth onto the PCB.

[crazydean]

Who did the work? If it wasn't cleaned after the caps were removed, it could still be shorting out

[Stupid Dufus]

Thank you for the responses, and sorry for the delay!

I did clean it up with 99% isopropyl after I removed all the caps initially as there was quite a bit of leakage at that time.

The work was done by a place here in Japan called BEEP. Specializes in old game consoles, arcade boards, etc.

Here are pics that BEEP sent me back after caps were installed but still no sound or video.
Pic 1
Pic 2
Pic 3
Pic 4

If needed, I can open it up again and take more shots.

[thesteve]

no sound or pic.........is it on?
screen white/black/other?

[Stupid Dufus]

Oh, it definitely receives power. The LCD lights up.. but black.

I've tried powering from an official North American AC adapter (with step-down transformer) as well as fresh batteries. Same results either way.

Audio: Sometimes when it turns on, there's an audio buzzing from the speaker, but usually it's just a faint hum that I hear in a Turbo Express that was recapped.

Video: Sometimes the LCD powers up black and sometimes it powers up with a purple image. I'm testing with HuCards that work in other PC Engine consoles.

Screen 1
Screen 2
Screen 3

[thesteve]

if the contrast knob works, it could be a chip issue, if not it could be a bad screen/T500 or related circuit
the chip issue would explain the no sound as well
black screen has been mostly work ram failures, but could be circuit related as well

[Stupid Dufus]

Contrast nob definitely works. Can adjust with no issues... other than no picture =P

If it is a chip issue, is it repairable? Or is this now a paperweight?

[haightc]

I might also check the isolator L900, when  recapping mine the isolator literally crumbled into bits when I removed the foam.  I would also inspect and test the back light transformer (t900) as well.   To me it sounds like you have some sort of voltage supply issue.     The work looks pretty clean however the photos, however when the diode or resistor fails it's not nearly as spectacular as traditional caps.

[Stupid Dufus]

For the isolator L900, would it just be a visual inspection? Or is there something specific I need to check for, like continuity?

Same for the t900 transformer?

[haightc]

In regard to the isolator, obviously you'll want to visually inspect the unit. You should want to test the continuity of isolator and the resistance.    Then check the voltage output of the transformer and make sure it's stable.   I think it's supposed to output 35v.   Audio noise in the circuit is usually indicative of transformer failure. If the voltage output is stable from the transformer verify current output of the isolator.

[thesteve]

light on, contrast working T900 and L900 are good
the system didnt boot
it could have a bad chip or damaged trace/bent pin
in most cases it would fail white/colored screen
chips are replaceable, some have to be harvested