Back-Story:I bought a PC Engine Duo from Japan. The seller stated that HU-Cards are playing, but CD-Rom Games would not load.
It came without any cables or controllers. So I had to make my own AV-Cable and power supply (used a 9v 1A).
Symptoms on arrival:Right from the start it showed garbled graphics on the BIOS screen, but I had to wait for my Turbo ED and a Controller to check more. I noticed that when I quickly turned the console off and on again, the BIOS screen was perfect. So I assumed it had to do with the caps.
After replacing all the caps the problems remained the same unfortunately. (I soldered in C525 the wrong orientation at first, but corrected it later without any difference.) When my Turbo ED arrived the menu was always showing correctly, but games sometimes had glitchy graphics, sometimes not. It almost felt as if the console needed time to "warm up".
The CD spindle actually only needed a little push to make it work again. Seems like it just got a little stuck at some point. I didn't bother too much adjusting the laser (it would only read to around the 50 min mark), since CD games also had glitchy graphics.
What I did so far:None of the caps seem to have leaked badly, though some had corroded pads. But I was not able to find any bad traces on the board. So I decided to reflow all chips in case one of the legs somewhere wouldn't have contact. I might went a bit to far here re-soldering literally every "chip", even the smaller IC's and mosfets. I used a soldering iron, lots of flux and only quickly touched the legs. After that the symptoms changed / got worse a bit. I accidently bridged two pins on the largest chip on the bottom (the NEC D91317GD somewhere between 70 and 75 I think). I don't know if this caused any damage.
I also removed another bridge between Pin 41 and 42 on the HuC6270 later on. After this the graphics are not messed up any more.
Status now: 1. Somewhere in the process the laser got stuck on the outer edge a would not move anymore. I had to bring it back to the center by hand, but it won't read discs anymore (no spinning). The BA6290A on top of the board becomes extremely hot.
2. I get some distortions on screen that are best visible on black background (attached a video), that start to appear a minute or so after turning on the console and getting worse. The colors are also a bit off. Like the text on the BIOS screen turns from blue into some sort of cyan. This also applies to HU-Card games.
No idea if the 1. problem causes the 2nd. I can not find anything obvious on the board anymore. Any ideas where to start fixing the problems?
(It's getting worse at 0:36)