I just acquired a VA4 Mega Drive in hopes to use it as my main MD system since it doesn't have TMSS. It was pretty dirty... but it works.
As I do with all of my Mega Drive/Genesis consoles, I replaced all of the capacitors, because why not? The system is approaching 30 years of age.
Before I changed all of the capacitors, I decided to wash the PCB in the sink, because it was very dirty. I do this to JAMMA boards all the time with no problem. After washing, I let it dry out for 6 hours before proceeding with the capacitor replacement.
After replacing capacitors, I have encountered a strange problem. The left audio channel doesn't work. I have a US Genesis that works, so I decided to swap components between the two systems to rule out what is not the problem. The headphone jack, the Sony CXA1034, and the volume slider are all working properly.
I tried to bypass the headphone amp by soldering L and R RCA jacks to the CXA1034 pins 1 and 8 and the problem still persists. No left channel. I also tried the mono output on the DIN connector, left is not working on the 240p test suite left/right test.
So this leads me to believe the problem is somewhere before the headphone amp and mono opamp mixer. Maybe a cap I replaced is bad but it seems unlikely. I only use high-quality caps.
Any ideas?