Some capacitors and the volume pot were missing, so I replaced these.
The game booted but with corrupt background graphics. It wouldnt coinup and in when set to freeplay it would play but character would not move left. The sound was completely missing.
Graphics;
I looked at the schematics and found the control logic for the graphics ROMs. Probing various chips around this area found a LS86 @9F with stuck outputs. Piggybacking this made a small difference so pulled it and it failed. Replacing it made the graphics slightly better. Then found a ls174 at 9G with dead outputs. Replacing this restored background graphics but some colours looked off and there was an interference pattern appearing that got worse with time. Probing back from the colour proms I found another LS174 at 7I with dead outputs. Replacing this restored the graphics.
Inputs;
Coin and p1 left were both multiplexed through a ls253 at 3E. Replaced this and inputs started working.
Sound;
Amp was dead (finger test) replaced it and got speaker hum but no sounds. The Z80 at 4E is the sound CPU and was getting clock signal and reset pulse at boot but did nothing. Suspected it was dead so replaced it and some sound returned but some random sounds were playing and the music was missing. Suspected the 6116 RAM at 7E so pulled it and it failed. Replacing it restored the sound properly.
The game booted but with corrupt background graphics. It wouldnt coinup and in when set to freeplay it would play but character would not move left. The sound was completely missing.
Graphics;
I looked at the schematics and found the control logic for the graphics ROMs. Probing various chips around this area found a LS86 @9F with stuck outputs. Piggybacking this made a small difference so pulled it and it failed. Replacing it made the graphics slightly better. Then found a ls174 at 9G with dead outputs. Replacing this restored background graphics but some colours looked off and there was an interference pattern appearing that got worse with time. Probing back from the colour proms I found another LS174 at 7I with dead outputs. Replacing this restored the graphics.
Inputs;
Coin and p1 left were both multiplexed through a ls253 at 3E. Replaced this and inputs started working.
Sound;
Amp was dead (finger test) replaced it and got speaker hum but no sounds. The Z80 at 4E is the sound CPU and was getting clock signal and reset pulse at boot but did nothing. Suspected it was dead so replaced it and some sound returned but some random sounds were playing and the music was missing. Suspected the 6116 RAM at 7E so pulled it and it failed. Replacing it restored the sound properly.
