NEC TG-16/TE/TurboDuo > TG/PCE Repair/Mod Discussion
PC Engine GT - No Video or Backlight
WaldoX:
Hello everyone, I am obviously new here, but this seems like the perfect community to try and get some assistance. I have done a lot of googling already, but have not come across a thread with my exact issue.
I recently purchased a PC Engine GT from Japan. When I first received it and tested on batteries, there were no signs of life at all. Now, I wish I had left it running for a minute to see if any sound started (I have one game to test with), but I didn't. I flipped the power swtich, saw no signs of life, and turned it back off. I wish I had played with the volume and brightness wheels, but I can't say that I did. I know, I did a terrible job of inspecting it's operation, but I expected to have to recap it anyway, so I think that's why I glossed over it. My bad! One of the battery terminals had quite a bit of corrosion, so I also ordered an AC Adapter and tried with that once I got it, but same results (and same crappy testing on my part).
Ok, so I did a full recap last weekend, and when I first tested the system after finishing, it appeared to still be dead, which was quite soul crushing, but luckily I left it running, and after 20 or 30 seconds music started playing! Nice and loud too! It also seems like the game responded to me pressing start. Sadly though, the screen doesn't do anything at all. Not a flicker. No video, no backlight.
Seems like maybe it's not getting power? I have a multi-meter, but I'm quite new to all of this and would love a little help in knowing where to test for voltage to the screen, and any other advice you folks may have!
P.S. While most of the old caps had corrosion around their legs, none of them had spilled their contents and damaged anything around them. I got the old caps off, and cleaned up the pads and all looks good to me.
Thanks again!
WaldoX:
Hello again, I had a chance to do some more testing, and it appears I'm not getting voltage at the red connector for the screen. I found a thread at badcaps.net that suggested some voltages to check:
--- Quote ---Also, try for the following voltages at these Test points:
TP500 30v
TP501 -24v
TP502 5v (ish, you will see it from 4.8 to 5v depending on factory)
The 2x Variable Resistors adjust the supply rails:
VR500 LCD Voltage Adjust (-24v)
VR501 System 5v Adjust
--- End quote ---
Here's what I got:
[*]TP500 30.1
[*]TP501 -24.3
[*]TP502 4.91
[*]VR500 -23.1
[*]VR501 3.1
[/list]
None of those seem off by too much except for VR501, but I don't know enough about any of this to know if that's a problem. HOWEVER, like I said, I also tried to probe the power connector for the screen directly, and cannot get any sort of voltage reading out of it!
I also don't get anything from TP901 which is next to the connector, but I also don't know what I should get there.
Click here for a closeup of the area around the connector.
Notice what might be cap fluid lurking around? Do you think there could be damage under those grey blobs that is preventing those pins from getting power?
Any advice is appreciated! Thanks!
Keith Courage:
Check the traces+connections for both 4.7UF capacitors and the two 100UF caps near them. Make sure the same voltages are going through the via holes since these are what normally short out from old cap leakage.
WaldoX:
--- Quote from: Keith Courage on October 08, 2021, 01:33:42 AM ---Check the traces+connections for both 4.7UF capacitors and the two 100UF caps near them. Make sure the same voltages are going through the via holes since these are what normally short out from old cap leakage.
--- End quote ---
Hello and thanks for the reply! I have carefully inspected the areas you mentioned and don't see any broken traces or connections. I have tested voltages at the capacitors you mentioned, and I tested many many vias in the area. Here are some pictures showing my results. I think there's an obvious problem at CC503 with it reading 0 volts? The vias right next to it are reading well, so I think I had better pull that cap and see what it going on under there. Any other advice?
WaldoX:
And here are the other 2 pics:
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