Mar 202019
 

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’ :

Konami ‘007593’ & ‘007327’ reproduction

So I assembled and installed a unit :

Board booted into game with no further issues.Repair accomplished.

 Posted by at 10:20 pm