9 May 2019

Raiden - Seibu 1990 #2 (repair log)

Game was dead, no main or sub CPU activity, however sound section was alive since adding a coin would make the associated jingle play.

This was the first revision of the hardware used by Seibu for Raiden, a real nightmare for repairers:
- 18 CPLD (most undumped, few dumps I've found turned out to be incorrect due to most devices being registered)
- 12 SMD custom chips
- 6 SIL custom chips
- few others DIP/SDIP custom chips (e.g. YM3931, etc.)
- many custom SDIP mask ROMs
Seibu probably went this route to discourage piracy, at the price of an overly complicated design, a much more simpler hardware could have done the job perfectly.

I probed main and sub CPU and found there was activity on buses for a fraction of second only then nothing. I was a bit stuck since few signals made no sense: some LS245 had their /OE signal stuck high, putting all outputs in high impedance, although their DIR signal was toggling, Altera chip for sub CPU had 2 floating inputs (pins 5 and 9) coming from the PEEL18CV8 stamped RD016, etc.
I put the board aside for a couple of days, time to elaborate a plan. Having a fully working Raiden I though I'd make few experiences with it. Pulling sub CPU ROMs revealed main CPU was still able to start and maintain its activity. Thus first problem to solve was to get main CPU to run. I continued probing on the main CPU, associated ROMs and RAMs, and nearby PLDs when I found one input (pin 11) of RD002 (U0172, PEELCV8) was floating. This was interesting since that chip generates the /CE signals for ROMs and RAMs and I had found before ROMs 3 & 4 were permanently selected (always low) and the other pair of ROMS (1 & 2) so as RAMs were never selected (always high). I followed the trace and found a point of corrosion on a via near the JAMMA edge. I clean the rust and exposed copper and for sure connection was low on half a millimetre between the via and the trace:


Once patched game then booted and was almost fully working! Except sprites were "cut":





Swapping the daughterboard (OBJ1) with a known working one informed me it was the culprit. Upon close inspection I found several lifted pins on several SMD customs chips:


I reflowed all of them and sprites fully reappeared:




Game fixed.

P.S.: I had used the UEC-52 (SIL22) custom chip from that board to repair an other Raiden board but in the meantime I'd also ordered a replacement part from Caius from jammarcade:





I decided to install the replacement on that board and can confirm it works per fectly. Thanks Caius, good job!





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