Hatta, on Thu Nov 19, 2009 1:58 PM, said:
The big one in my mind is the crappy audio on anything but the first model Genesis. Glad that can be fixed with a mod these days though.
How are the capacitors in these things by the way? Are they generally in need of replacement?
My early Genesis hasn't really worked right since it was about 1-2yrs old.
Recently I fixed a video problem, which turned out to be caused by bad caps.
The bad caps are Chhsi, which are a notoriously bad brand. Every single one I removed tested way out of spec, while the other brands in the same Genesis were still good.
If you see a Genesis with Chhsi caps in it, you can assume they're bad.
They're also a pain to remove properly. I'm not sure if the board even has a through-hole via or if it's just 2 separate solder pads on top/bottom. I suspect the latter because Sega soldered the tops separately.
I had a hard time not damaging them. It's much easier to do the same job on modern PC motherboards.
I also noticed a very bad solder joint under one of the video RAM chips.
The remaining issues are lockups/sound glitches (Z80 problem?) and controller glitches. I noticed a particular component that triggers instability when I nudge it, so maybe I've found the problem.