Another Haunted Castle repair log.
Actually it was the japanese revision called ‘Akumajou Dracula’.The board was in clean condition:
But this was the scenario after I powered it up:
Vertical lines across the screen and missing sprites were the most noticeable issue.As usual I started my troubleshooting with a visual inspection focusing in the tiles and sprites generation circuit and I promptly noticed this:
Someone (for sure not a great expert…) previously attempted a repair and replaced the two ZIP M5M4464L DRAMs @H3-H4 but mounted them backwards.After correctly installed a pair of new chips I got this improvement:
There were still jailbairs across some sprites.From my experience in past repairs I knew this kind of issue are caused by the other couple of ZIP DRAMs @L20-L21 (where the ‘007121’ custom @J16 accesses to)
I replaced them and sprites were fully restored.I was declaring the board as fixed but I noticed that some layers (more than the colors) were missing on some backgrounds like title screen :
With the help of schematics I went to check all the parts of circuit that could be involved until I notice that the input pin 14 of a 74LS399 @D16 was stuck low while all other were correctly toggling:
If I shorted this pin with the adiacent one (13), all the layers came back although some colors were wrong:
The signal labeled on schematics’GA1C02′ is generated by the custom tilemap generator ‘007121’ @J16:
So this lead me to play the card of replacing this ‘beast’ in PGA package of 208 pin:
Armed with a heat gun, I removed it :
and transplanted a good know working one taken from a Combat School donor PCB:
And I was right since since this fixed completely the board:
End of job.