Jul 122018
 

Received from Austria this Devastators PCB (manufactured by Konami in the distant 1988)

The board was constantly watchdogging sign that no valid code was executed :

Probing the HD63C09E main CPU revelead some address lines were dead:

I removed it :

Trying the CPU in another board confirmed it was really bad so I replaced it.The board booted up but it was failing the POST showing two bad devices which at fist glance I could not recognize due the complete lack of graphics :

Thanks to MAME I figured out they were the ones @C11 and C14 :

On PCB they are the two 2k x 8-bit static RAMs (Motorola MCM2016 used) which are part of the palette colors circuit

Probing the one @C14 revealed stuck data signals:

RAM chip failed the out-of-circuit testing:

Now the board booted into game but with severe graphics issue : the backgrounds had wrong colors and sprites were missing.Sound was absent too:

I dumped the four OTP MASK ROMs that store tiles data and found three bad ones :

But this made no real improvements.Board is almost fully populated with Fuitsu TTLs so I went to test them in-circuit with a logic comparator starting from this part of circuit which is involved in color generation  :

I found five bad mutiplexers with floating outputs:

This restored correct backgrounds:

I decided to troubleshoot for first the lack of sound.Found in rapid succession these bad ICs:

  • YM2151 (with serial data output pin stuck high)
  • sound RAM and ROM
  • two 74LS74 @G5-F10

And a 74LS273 @B7 with some floating outputs:

Sound was back :

Now the lack of sprites.MASK ROMs check reported two bad devices @H4-K4 which are the ones  storing sprites data:

This particular PCB uses a bottom ROM board with sprites and audio samples ROMs :

But the top board can also host three 4Mbit devices for the same data so you can get rid of the ROM board :

This is what I opted instead of troubleshooting it since all the splitted ROMs were soldered in.I programmed three 27C400 EPROMs with MAME dumps:

The last issue I had to fix was releated to inputs, P1 UP was not working.Using schematics I quickly found and replaced a 74LS253 @E13 with a bad ouput :

Board finally 100% fixed and another battle won against Evil Konami and Fujitsu with this big booty:

 

 Posted by at 6:14 pm

  3 Responses to “Devastators repair log”

  1. Congrats on this repair!
    A lot of work I can see. Only overvoltage can explain so many chips to fail (except for the Fujitsu ones) don’t you think?

  2. Thanks.It has been a long repair more than an hard one.
    Yes, overvoltage can be a cause but also abuse in my opinion.Don’t forget these boards were used to run uninterruptedly for days and days (if not months) in the arcades.

    • Sure but I think as soon as the first chip would have gone bad the board would have been pulled from operation. Then you would expect to find one unique fault, not several ones not related to each others.
      Well, I guess we’ll never now what happened to that board but I’m always really curious when I encounter this kind of scenario.

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