PCB Repair Logs – Page 34

Dogyuun repair log #1

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Dec 192017

Got from Portugal this almost mint but not working Dogyuun PCB, a shoot ’em up released by Toaplan in 1992:

On power up, after the system got initialized, board sat on a black screen.Main 68000 CPU was halted at this point,no sign of activity on all busses and control lines:

Usually this happens when a device (most of times RAMs) in the CPU address space doesn’t answer to initial check.So I went to probe RAMs and found that the two Mitsubishi M5M5178 @U46-U47 (8k x 8bit static RAM compatible with 6264) had /OE and /WE lines stuck (they are addessed by one of the GP9001 ASIC so the are VIDEO RAMs)

When I went to piggyback the one @U47 the board successfully booted and entered in game:

The chip obvioulsy failed the out-of-circuit test:

The game was fully playable but while testing I noticed some of the player 2 inputs didn’t work, in particular LEFT RIGHT, BUTTON 1 and 2 were responding at same time when one of them was activated.This can be clearly seen in the input check of TEST mode:

Checking with a logic probe the relevant pins of the JAMMA edge connector revealed that they were floating when usually they must stay in HIGH state when not activated (and then LOW when input is activated).Pull-up resitors or resistors array are used most of times to keep the inputs in HIGH state.When I went to check with a multimeter the 4.7K array @RM7 I found no reading from pin 5 onwards :

So it was most likely internally cracked.Indeed, once removed, it fell off in two parts:

Fitting a good one cured the issue.Board 100% fixed.

TH Strikes Back repair log

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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.

1941 : Counter Attack repair log #2

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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…

Pac-Mania ROM board repair log

PCB Repair Logs 4 Responses »

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:

Defender repair log #2

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Nov 302017

After reparing my Defender ( see this log: https://www.jammarcade.net/defender-repair-log/ ) I noticed that the screen had some horizontal lines of different brightness.

At first I didn’t give much attention but then I decided to look at this issue deeper.

Moving the screen left and right with the monitor commands I noticed these defects:

Having the experience of a similar problem on my Burnin Rubber ( https://www.jammarcade.net/burnin-rubber-repair-log/ ), to me it was clear there was a video blanking problem

With the schematics in hand I found this circuit:

Signals from 7420@5C were good so I started probing the 7400@4B

All signals were good except that pin 10 was floating.

Looking at the above mentioned schematics, pin 10 is tied to the nearby pin 11!

I checked the board and found out that actually the pcb has no trace connected the 2 pins togheter!

No broken traces, it is actually simply not there!

I connected the two pins and…..

Game fixed!

Now I am wondering if my CPU board revision has a production error.

Searching on internet I haven’t found a similar problem therefore I would like to have a feedback from other owners of Defender if their pcbs has the trace or not.

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