Nov 052015
 

I had this rare Irem Ken-Go PCB (an undumped version included in latest MAME release) from my friend Joachim for a repair:

Ken-Go_PCB

The board played fine except for an issue where all sprites were formed but missing all colors appearing like black shape:

sprites_issue

Sprites generation circuit is located on top board where some customs lie:

Ken_Go_video_board

Documentation for this specific game was not available but luckily I could know function of the various customs by looking at the R-Type schematics and so identity the one involved in the sprites palette generation:

sprites_circuitry

The custom itself was marked ‘KNA91H014’ in 60 pins QFP package:

RSCN0698

Probing it revelead that inputs were fine but outputs had irregular signals:

KNA91H014_output

So I opted for replacing this custom (taking a good one from a dead Vigilante board)  :

KNA91H014_replacing

This was the right move since sprites were correcly restored:

sprites_fixed

End of job.

 Posted by at 3:57 pm