Mar 162016
 

Another Haunted Castle repair log.

Actually it was the japanese revision called ‘Akumajou Dracula’.The board was in clean condition:

Akumajou_Dracula_PCBt

But this was the scenario after I powered it up:

issue

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:

DRAM_H3_H4_backwardsm

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:

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)

DRAM@L20_L21

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 :

layer_issue

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:

stuck_data_74LS399@D16

If I shorted this pin with the adiacent one (13), all the layers came back although some colors were wrong:

partially_restored

The signal labeled on schematics’GA1C02′ is generated by the custom tilemap generator ‘007121’ @J16:

GA1C02_007121

So this lead me to play the card of replacing this ‘beast’ in PGA package of 208 pin:

007121@J16

Armed with a heat gun, I removed it :

007121_removed

and transplanted a good know working one taken from a Combat School donor PCB:

007121_donor

And I was right since since this fixed completely the board:

fixed

End of job.

 Posted by at 8:24 pm

  2 Responses to “Haunted Castle repair log #4”

  1. Sick repair!!! It’s always ultra rewarding when you swap a custom IC, and it ends up being the culprit. Great job!!

  2. Thanks.Yes, rewarding, especially when you deal with such “beasts” of custom IC!