Technos WWF Superstars arcade PCB Repair
Two different boards, both very clean with no physical damage. One booted to corruption, the other to a solid white screen. Logic probe showed the outputs on the palette RAM were dead on the second board, so when replaced it also booted to corruption like the first one.
The logic probe seemed to the show the 68000 CPU was not getting a clock signal so I probed the chips near the crystal oscillator and removed them from the board with a heat gun for external testing (but they tested fine). Strangely the game worked when I replaced the chip – that’s good but why? I then also found the second board would sometimes boot if I flexed the PCB near the crystal. My only theory is bad solder joints on the crystal that were fixed when the heat gun was used. The second board also boots consistently after re-doing the solder around the crystal even though it looked fine.
So board 1 now works 100% with sound. Board 2 boots but had some doubled up sprites at first (fixed by reseating the connectors between the two layers) and no sound. The sound amp seems to be working, but at least one problem seems to be the YM3014 DAC chip. The logic probe shows pulsing on the digital inputs, but the voltmeter shows no movement on the analog outputs (unlike the working board). Right now I don’t have a spare to check.