Got from USA this original Contra (by Konami) PCB for repair :
Board simply booted to a black screen, time to investigate then.A closer inspection revealed the 3.58MHz oscillator was missing:
This provides clock for the YM2151 IC as you can see on schematics:
I fitted it but obviously board was still dead so I focused on the main CPU ( an HD63C09) dumping the two program ROMs:
Analyzing dumps revealed that somebody installed another sound ROM (like the one @12A) in the socket of the program ROM @18A, you can see in above picture that indeed there are two devices with same ‘633E01’ label.I programmed an empty 27256 EPROM but board was still not booting.Looking better at PCB I noticed the ‘007593’ palette custom IC @1F was damaged :
The package was really cracked isolating pin 24-28 from the rest of its internal circuit :
The custom ‘007593’ exchanges 8 bit of color data with main CPU and other devices through pin 21-28 as per schematics :
This did make sense so I promptly removed the custom and installed some 1.778mm headers:
As some of you may remember some time ago I made a reproduction of the ‘007593’ :
So I assembled and installed a unit :
Board booted into game with no further issues.Repair accomplished.
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