LIghtning Fighters repair log

Received for repair this Lightning Fighters PCB (a vertical-scrolling shoot 'em up developed and released by Konami on arcade in 1990)

Board was labeled with sprites and sound issues, indeed I got wrong colors on some sprites 

I already experienced this kind of problem on this and similar Konami hardware, the part involved was most of times the '053251 custom ASIC which is a priority encoder and sprites/backgrounds mixer 

 I went to check it with a logic probe and promptly found a floating pin (30)

This is an input to the custom IC so I visually inspected the board and found some exposed traces on solder side (soldermask was removed)

I checked them all and indeed the one routed to pin 30 of the '053251' custom IC was broken.I patched it with some 30AWG wrapping wire but sprites were better but not yet pefect.So I kept probing the '053251' custom IC and found a stuck low input pin (38)

 

With the help of schematics I traced it back to pin 112 (labeled 'OB08') of the '053244' sprites generator (along with its companion '053245').

I lifted ths pin and it was still stuck low meaning the custom IC was internally faulty.I took a spare from a Premiere Soccer donor board (actually the later revision '053244A', fully compatible and  interchangeable with the '053244') 

This fixed the sprites completely so I focused on the sound issue.The music was present but many sound FXs were missing or incorrectly played

Sound samples are stored in a 4Mbit MASK ROM (at location C5) and played by the '053260' PCM/ADPCM custom IC

 

I performed some MASK ROM checks that most of times the device @C5 was reported as bad

Also the sound test was silent, I could not hear anything when I sent commands to play the samples

Sure enough I removed the 4Mbit MASK ROM 

I read the device in my programmer and surpringsly the dump matched the MAME ROM file but I decided anyway to replace it with a programmed 27C400 EPROM 

This was the right move since all sound FXs were totally restored.Board 100% working again and another successful repair.