I Checked the psu again last night, I turned it up a bit to 5.1v. I am only getting 4.71v at the pcb. Is a drop of 0.39v acceptable? I also set my meter to the AC 200v Range, and measured the 5v rail, it measures 10.3v. How can the ripple voltage be higher than the DC Voltage? Does it sound like the psu could be causing the interference? and does it need replacing, or the caps doing in it?
I have another problem now too, my Joysticks and buttons weren't working I checked the wiring and the GND wires on either end of the jamma connector weren't connected together, so I linked them all up to GND and now I have the coin mech working, joystick and buttons working but the interference is worse than ever, and now the graphics are glitching too with whole sections of the background disappearing, could that be because I have lowered the voltage and the board is struggling or is it likely to be an eprom problem or dirty contact or something else? I put two more videos up on youtube showing the interference and the glitching.
1. Glitching
2. Interference
Update..... I still have the interference but the glitching has stopped since I turned the power back up, I replaced all the electrolytic caps in the sound section and the 12v &5v filter caps near the edge connector (Thought it might fix the crappy sound but it didn't, it may just be a crappy speaker) Anyway after doing the caps I adjusted the 5v rail so it was about 5.08v at the board and since then the glitching has stopped.