PCB Repair Logs – Page 32

Konami Viper repair log

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Feb 142018

I’ve been playing around with a couple of Konami Viper PCB’s that Olly sent me recently.

The idea was to get a working PCB for his Silent Scope Fortune Hunter.
This board set was non booting and a quick visual inspection showed some signs of ‘man-made’ damage.
First was the 3793-A voltage sense IC was a bit mangled which had lifted most of its traces. Chances are this was causing the PCB to not boot as this chip is responsible for making sure the voltage levels are what they should be.

As its a small pin count it was fairly easy to patch up the traces.

The second issue was the DS2430 IC has been removed. Luckily this was provided in a small bag so I was able to refit it (after dumping it). This IC is in a TO-92 package and is responsible for providing one aspect of the security on this hardware. I never took any pictures of this but its only 3 legs to solder and there was no damage.

After dealing with these the PCB booted right up
Taking pictures of this was really hard due to the amount of glare my cheap screen gives.

From here I can get the game to boot up but I cannot test beyond that. I will send this PCB back to Olly and hope it works out for him.

Sunset Riders repair log #7

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Feb 102018

Still another “portughese” PCB, a Sunset Riders :

The board was unstable, most of times it didn’t boot and kept resetting (watchdog active), some times after some reboots it got past the self-test and entered in game but sprites were missing.If I pressed/flexed the board, they appeared.Here’s a video for a better understanding:

I noticed someone previously tried to fix this issue by reflowing the two sprites generator ‘053244’ and ‘053245’ (forgetting to remove flux residuals )

The reflow was done properly but it was not enough, anyway there was for sure a bad contact in this area. At a closer inspection I found that a pin of the near ‘054358’ custom had its pad detached from PCB, this caused intermittent contact with its trace.Here’s a close-up under a microscope:

I promptly restored the connection, in this way the board booted all the time with sprites too.But playing the game I noticed some little glitches :

The glitches got worse if I put my fingers on the solder side of the two palette SRAMs (2K x 8-bit devices)

The one @14D was already replaced and socketed, probing the other one @13D with a scope revealed unhealthy signals on some data pins :

This lead me to remove the device and test it ouf-of-citcuit where it failed:

Replacing the RAM fixed board completely, another successful repair in the archive.

Aliens repair log #4

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Feb 092018

Got always from Portugal this Alien PCB:

As often happens on this hardware the sprites had jailbars thru:

Board uses 4Mbit MASK ROMs to store GFX (sprites and background) data that are quite prone to failure.I launched a MASK ROM check that reported a bad device @K8:

I removed it and my programmer warned me about pin 13 (data line D0).I tried the dump in MAME and I could reproduce the issue :

I replaced the MASK ROM with an equivalent 27C400 EPROM :

This fixed issue and board completely.End of job.

Bomber Man World repair log

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Feb 072018

Received from Portugal a batch of faulty PCBs for repair, there was among them this Bomber Man World (on Irem M97 hardware)

The PCB was working fine except for the sound, you could only hear some scratchy noise and also video output was affected showing some kind of disturbs:

This is scenario I faced many times during repairs and the cause was always the same : the electrolytic capacitors.In particular Irem boards suffers from the “brown ELNA” syndrome and this was not an expection.I went to measure capacitors with my ESR meter starting from the 470uF 25V one @C203 which filters the +12V routed to to sound amplfier.My meter didn’t display any reading meaning the measured ESR value was out of range (from 0 to 99 Ohm on my meter)

Probing the +12V line with a scope confirmed there was some ripple (no longer filtered by this capacitor)

The out-of-circuit testing confirmed the high ESR and bad capacitance :

Fitting a good capacitor restored loud and crisp sound.End of job.

Cadash repair log #2

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Jan 242018

Received from Spain this Cadash PCB (it turned out to be an undumped Spanish version)

Board was stuck on a garbage screen :

A clicking sound suggested that the watchdog circuit was active, infact both /HALT and /RESET lines of 68000 main CPU were going LOW and HIGH in an endless loop.At first glance I thouhgt the Taito custom ‘TC00220IOC’ (responsible of generating the master reset for whole system) was faulty since this is a very prone to failure part :

But I was wrong since I replaced it with no changes.Probing the 68000 CPU I found that data line D0 (pin 5) was stuck low, using a multimeter revealed it was shorted to ground:

Looking at solderside I traced the pin back also to pin 25 of a Fujitsu MB8422 Dual-Port SRAM (part of linking mode circuit)

I cut the trace and the short was cleared (so the I/O pin of the MB8422 was internally shorted).Finally board booted into game:

But I noticed two problems : the buttons of the Player 1 were not responding and sound had rustles, you can hear it from this video :

As for first issue, using a logic probe revealed the relevant pins of JAMMA edge connector were stuck LOW :

Inputs of an arcade board must be HIGH when not activated, they are usually pulled in this state by resistors.Indeed, tracing back the pins of the three P1 buttons from JAMMA connector lead me to some custom resistor network:

The array @RRC1 was the one involved so I removed and replaced it, this fixed the controls issue.As for sound, using an audio probe I figured out that the bad audio was coming out from the TL074 OP-AMP from Texas Instruments (which are really prone to failure, have replaced tons of them)

Replacing it restored a crisp sound.End of job

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