Robocop 2 repair log

 Got for repair this original Robocop 2 PCB by Data East :

Board booted up and plays but sprites were completely absent :

Sprites are generated by the surface mounted custom ASIC marked '52' :

Schematics for this board are not available but I was able to find the pinout of this custom IC on the ones of Desert Assault.There are some input timing signals to the '52' custom IC, when I went to probe them I found pin 98 (labeled 'VCNT' on schematics) stuck high :

 

 I traced the pin back and found on the path a gouged trace on solder side :

I patched the trace with some wire wrapping wire and sprites came back :

Job done, anpther repair successful accomplished.

1942 repair log

Got for repair an original Capcom 1942.

It's a two PCB stack made of a CPU board

and a VIDEO board

When I applied power the board booted but I could not coin up

Looking at schematics the coin input from the edge connector is routed to pin 14 of a 74LS367 @A6 on CPU board

 

 

Checking it with a logic probe revealed a floated signal (usually inputs are in high state pulled-up by resistors)

Using a multimeter I measured few Ohms of resistance between pin 14 of the 74LS367 and GROUND (whereas usually it should in order of MegaOhms)

I pulled the IC :

 It passed the out-of-circuit testing on the Retro Chip Tester :

 But it failed the one of my ChipMax2 programmer :

I fitted a socket and a good IC :

 This fixed the issue, the game registered again coin input.No other problem was found therefore board 100% working again!