PC engine GT - no picture or sound, recapped - suspect voltage problem

[Turbofly]

Hey all,

I am new to the forum, and also a new PC Engine GT owner.  Of course it arrived with the usual capacitor leakage issue.  The backlight would come on, and there was no sound, but if you tilted the GT just the right way you could just make out the faintest of graphics.  I ordered a cap kit and have installed it, (all of the caps, even the one under the shielding).  There has been no change.  So after and little bit of internet searching I found this forum, and read through this thread: https://www.pcenginefans.com/forum/index.php?topic=5015.210.  Posts from thesteve and Keith Courage seemed to be most applicable to my GT.  I got out my multimeter and checked the (-) pin of the 22uf cap near the VR500 pot, and I get -24V like I should.  However, when I take a reading at the top pot, VR501, I'm only getting around 3V, when I should get 5V.  I read that thesteve had this issue and found that R506, a 1K resistor, had cracked.  I tested R506, (in circuit), and got a reading of just under 1K, so I don't think this is my problem.  I've also tried adjusting VR501, and it'll decrease in voltage, but will not increase much past 3V.  I don't know anything about the 5V circuit in a GT, and I am not sure where to start troubleshooting or if the legs of VR501 are even the right spot to take a 5V reading from.  Any ideas you guys on this forum can suggest would be greatly appreciated.  Thanks in advance.

[Keith Courage]

There could be a chance that there is some left over old cap gooo shorting things out somewhere on your board. Start by double checking connections and via holes in the areas where there was a high amount of cap leakage .

[Turbofly]

Hi Keith,

Thanks for the reply.  I've cleaned all of the leaked areas with IPA.  I've also checked continuity from each of the 2 legs of all of the new capacitors to a via or other point on its trace.  everything checked out good.

[Keith Courage]

If someone doesn't get to this before me, I should have an express open on my work desk within the next couple days. I'll take a look then and let you know where 5V should be coming from.

[MNKyDeth]

I know you said you cleaned with IPA, it might be worth taking the really small legs from the caps if you didn't use surface mount caps. And poking them through the holes on the pcb to ensure the thru-hole traces are clear of any residue. If you can measure the proper volts on one side but not the other your problem is there.

I typically find voltage issues around the ap-amps (in the regular consoles)... But those traces that go through the PCB fill up with crap and cap fluids. Cleaning them out and measuring voltage on either side sometimes has to happen. And if you find one that is reading different from one side to the other. Rub some of the coating away and solder the cap leg to both sides of the hole to reinforce and complete the trace.

[Turbofly]

Thanks for the suggestion MNKyDeth, I'll give it a try.  I've got lots of those legs, I always keep them for bridging points together.