This PC10 motherboard had been stored some where damp so all the sockets were nasty and corroded. The first thing I had to do was replace them all.
Once that was done and the roms confirmed good it was time to test it.
The top screen displayed this garbage and the bottom screen displayed nothing as the game (Super Mario Bros) was not running.
From a previous PC10 repair I knew the ram on these has a high failure rate so I desoldered and tested all the ram. Two were bad and replaced but the board still didn't boot. I then found a bad 74LS245 buffer next to the NES cpu, that's got to be it right? nope no change.
I eventually found a 74LS11 in the middle of the board was bad and piggybacking a good one on top the board would finally boot.
Everything looked good but I couldn't start the game, coin up worked and game select but not the start button. There are some very nice schematic scans for PC10, using these I traced the issue down to a bad 74LS165 near the edge of the board.
3 bad logic and 2 bad ram (that I threw out before taking the picture).
Still a bit dusty but all new sockets and new parts fitted. :)
Repair complete.
