Caius

Dec 102017
 

Received from Uruguay this ‘TH Strikes Back’ PCB (a.k.a. Thunder Hoop 2 by the spanish Gaelco)

Board played with all the graphics scrambled and messed up:

Doing a visual inspection I found a severed trace on solder side:

Patching it restored graphics but playing the game I noticed that the sound samples were all wrong and played randomly:

Samples are generated by the usual OKI MSM6295 PCM chip, given the high rate of its failure I went straight to replace it:

This gave me correct sound.But while testing the board, it suddenly committed suicide:

Like many other Gaelco boards this PCB uses for protection a Dallas DS5002 MCU which executes code stored in battery backed-up SRAM.When the contents of the SRAM get lost due a low battery or other problem the board will no longer boot showing on boot the “COPROCESSOR NOT READY” or “COPROCESSOR BAD” error:

Thanks to the work of MAME devs (Peter Wilhelmsen and Morten Shearman Kirkegaard) who dumps the contents of the SRAM now we can revive most of the Gaelco boards.The usual procedure to do it is well known and can be found on the net but it won’t work for some games that use a special register like Thunder Hoop 2.I was warned of this by Peter Wilhelmsen himself, he explained me how to properly desuicide this board (I will cover this topic in a proper post).I did it and board booted again but freezed everytime I started a game:

This issue had nothing to do with the Dallas DS5002 MCU, board was properly desuicided so I started to look elsewhere.Using a logic comparator in 68000 main CPU area I found a 74LS373 @D16 (involved WORK RAMs addressing) with a stuck LOW output (PIN 6).Measuring resistance to ground of this pin gave me only 10.9 Ohm sign that internal junction was almost shorted :

Once removed the TTL it failed the out-of-circuit testing in that exact pin:

Fitted a good TTL fixed the board definitively.Thanks again to Peter Wilhelmsen for his precious help.

 Posted by at 9:47 am
Dec 092017
 

Got this 1941 : Counter Attack (Japan release) B-BOARD for repair:

Game had some graphics issue on backgrounds:

I swapped the C-BOARD with the one from a Street FIghter II : World Warrior which mounts the same ‘CPS-B-05’ ASIC :

GFX issue disappeared so the fault was in the C-BOARD :

I was asking by owner to transplant the ASIC from the donor C-BOARD to original one, here’s a step-by-step collage:

The operation was successful :

Board 100% fixed and aesthetically like genuine, appearances count too…

 Posted by at 4:47 pm
Dec 082017
 

We have a new CPS1 PAL dump from the japanese release of 1941 : Counter Attack.PAL was a secured PAL16L8 located @1A on the ‘89625B-1’ B-BOARD.Dump has been successfully tested back on a GAL16V8 targeting device.Thanks to ‘robotype’ for loaning the board.

 Posted by at 11:16 pm
Dec 072017
 

Thanks to the courtesy of ‘philmurr’ we can host all his test ROMs for arcade PCBs.They are specific for :

  • Galaxian
  • Moon Cresta
  • Mr. Do!
  • Phoenix-Pleiads
  • Scramble

ROMs have ben tested on real hardware.You can read more about on UKVAC forums :

  • Mr. Do! :

http://www.ukvac.com/forum/mr-do-test-rom_topic361108.html

 

  • Galaxian, Moon Cresta and Scramble :

http://www.ukvac.com/forum/test-roms-galaxian-moon-cresta-scramble_topic355745.html

 

  • Phoenix and Pleiads :

http://www.ukvac.com/forum/phoenix-and-pleiads-test-rom_topic360891.html

Thanks again to him.

 

 Posted by at 8:41 pm
Dec 072017
 

Received from USA this Pac-Mania ROM board (Namco System 1 hardware) for repair :

According to the owner board played fine but mute, this was confirmed once powered it up.Using my audio probe I could hear sound on the input (pin 2) of the two LA4460 amplifiers but nothing on outputs:

At closer inspection one of them was literally blown up:

So I proceeded to remove both:

and installed two new spares and some thermal compound on heatsink:

Sound restored and board 100% fixed.End of job.

 

Update:

After converting this board to Splatterhouse I found that voices and other sound FXs were missing:

I quickly pinpointed the fault in a bad TL084 OP-AMP, replacing it cured the issue:

 Posted by at 4:22 pm