Mar 182019

Received from Portugal a cocktail version PCB of Indiana Jones, a real “holy grail” given its rarity.The peculiarity is that it runs on a different hardware than usual Atari System 1.Board is a two stack one made of a ‘main’ PCB :

And a ‘cartridge’ PCB :

All I got when I powered it up was a flashing ‘NO CARTRIDGE’ message on screen, watchdog was active and board resetting in an endless loop:

I started my troubleshooting with some preliminary things like reseating chips and ribbon cables.This worked in some way because it shutted down the watchdog and put the board in a static red screen :

Despite this state I was able to enter into TEST mode and perform all checks that were successfully carried except for the sound test which failed reporting this error :

The sound CPU is a 6502 located on cartridge PCB:

I replaced it with a good one and board booted into game.All seemed to be working fine, game was full playable but in a comparison with MAME I found that speeches were missing on my board

Here is how it should play:

I went into TEST mode and launched again a sound test.Music chip (YM2151) and Effects chip (POKEY) were tested good whereas the Speech chip test was silent:

The Speech chip is a Texas Instruments TMS5520:

Most of pins were inactive so,having a spare I replaced it but with no luck.Looking at schematics the TMS5520 exchanges data with the SY6522A (VIA, Versatile Interface Adapter)

I could not see anything else involved in the fault so I ordered the part which came into mail after some time:

I installed it and speeches were restored, board 100% fixed.Repair accomplished.

 Posted by at 4:07 pm

Extermination repair log and ‘X2-003’ – ‘RO-012’ reproduction

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Mar 112019

Some time ago I bought a lot of original faulty boards, there was among them a Taito PCB which at first gance I could not identify:

I could not power it up because there was a dead short between GROUND and +5V :

So I dumped some ROMs and it turned out to be Extermination, a vertical shoot’em up game (that runs on “The New Zealand Story” hardware) released by Taito in 1987.Someone previously tried to troubleshoot the board and cut one terminal of a zener diode thinking it was shorted but this was for +12V line protection whereas there is another zener diode to protect +5V which was actually bad causing the short to GROUND:

Once replaced the zener diode and cleared the short I powered the board up and it booted into game but sound was missing and colors were wrong with a dominant blue :

A blueish image means the RED color is missing or has some troubles.This was confirmed by the logic probe, the signal was indeed stuck low :

I could trace the JAMMA edge connector pin of RED back to a SIL component marked ‘RO-012’, a typical R/2R resistor ladder used as RGB DAC (one for each color).A closer inspection revealed the part was mounted backwards:


Reinstalling it with right orientation restored the RED color but image was now purplish :

This meant the GREEN color had some troubles.I located the relevant ‘RO-012’ DAC near the sound amplifier and found that some pins were shorted by a solder bridge:

Removing the bridge finally restored the correct colors :

Now the lack of audio.From signs on solder side I noticed someone previously reworked the sound section replacing the amplifier (an Hitachi HA1388) and potentiometer (and perhaps also capacitors)

Checking the +12V  confirmed this voltage was present on board but not on amplifier when I put the black probe of my multimeter on the two GROUND pins of the HA1388 (pin 4 and 9).At the end it turned out that who replaced the amplifier and potentiometer managed to lose their GROUND connection likely ripping off the rivets from the holes (power pins are always harder to desolder due to presence of internal planes).I restored the connections in this way :

Sound was back again.Board 100% fixed and job done.Before archiving this repair I took the chance to see if some parts (simple ones, not digital ASICs) were worth to be reproduced.I chose the aforementioned ‘RO-012’:

And the ‘X2-003’ :

The first, as said above, is an R/2R resistor ladder acting as RGB DAC, the latter is a capacitors/resistors array used for inputs but, unlike all the others, comes in a DIP16 ceramic package hence quite fragile.Reproducing them was straightforward :

 Posted by at 8:53 pm

Pac-Mania repair log #3

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Mar 092019

Got for repair from USA this Pac-Mania PCB on Namco Sytem 1 hardware.System is made of a larger ROM board:

And a smaller CPU board:

It booted to an ‘EEPROM ERROR’ message screen followed by some digits:

The EEPROM is a 2816 (2k x 8-bit) device located on CPU board:

I didn’t try to replace or swap this EEPROM since I knew it was not the cause of error.From my experience this is due to another IC that goes bad very often.I’m speaking bout the custom ’64A1′ located on ROM board @M4.Mine, indeed, was marked with a pencil as ‘BAD CHIP’ :

Technically the custom ’64A1′ is an HD63701 MCU in disguise with the exception of two custom opcodes.I already explained in a past post of mine how to replace it with a standard HD63701 MCU :

Namco System 1 custom ’64A1′ replacement

It’s what I did and this was enough to fix the board completely.Job done.

 Posted by at 7:36 pm

Sunset Riders repair log #9

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Mar 032019

Got from USA some faulty PCBs for repair, there was among them a Sunset Riders by Konami :

Owner told me he bought the board as working but actually it lacked of sprites when powered it up.I got, instead, different results.Sometimes the board passed the POST but then stayed on a static striped screen:

Other times it failed the self-test reported a bad device @12F:

The device in question is one of the two 6264 WORK RAM :

Probing this RAM with a scope revealed unhealthy signals on some data lines, here’s a comparison with good ones on the left of the picture below  :

I desoldered the chip, it failed the out-of-circuit testing of my EPROM programmer:

I replaced it and board finally booted into game but, as expected, sprites were displayed only half or totally missing:

I launched a MASK ROMs check which reported no errors :

But checking the two sprites MASK ROMs revealed the address lines were all stuck LOW, no activity :

Like in many other Konami PCBs all the sprites generation circuit is handled by two custom ASICs, on this board there is the ‘053245’ which generates the address for the MASK ROMs and the ‘053244’ which processes the data:

The first I tought was to replace the ‘053245’ which is what I did :

But invain because nothing changed.Then I remembered a past repair of a same board where the lack of sprites were due to a missing connection of the custom ‘054358’:

Sunset Riders repair log #7

Checking with a multimeter it seems this custom provides interface between busses of 68000 main CPU and the custom ASICs sprites generators.Having a spare I decided to replace it:

Sprites came back:

Board fixed and end of job.

 Posted by at 4:28 pm

Crude Buster repair log

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Feb 172019

Got from Portugal this Crude Buster PCB (also known as Two Crude outside Japan), an unusual and underrated beat ’em up developed and published by Data East in 1991:

Board simply booted to a white static screen:

Blank screen on boot.

The first thing I did was to check the main CPU (a custom 68000 marked ’59’) circuit and I found that both WORK RAMs (two 8K x 8-bit devices) has stuck data lines whereas address was correctly toggling :

The two RAMs are Toshiba TMM2063, we all know they are very prone to failure:


When I piggybacked them and got some errors (related to code execution) on screen:

Hence I decided to remove the chips:

WORK RAMs removed

Although RAMs were both tested fine in my programmer I replaced them and I got the board booting. Game was fully playable but some sound samples were wrong:

Samples are stored in two 1Mbit EPROMs and played by two OKI MSM6295 PCM chips:

Sound circuit overview

The two EPROMs were dumped as good so I fired up my audio probe and started to “listen” to output (pin 36) of the internal DAC of both MSM6295.The samples came out already corrupted from one :

I was about to replace the OKI MSM6295 when I noticed some solder residues on a couple of pins.I magnified the area with a microscope and found a solder bridge that shorted two address lines (pin 20 and 21)

Soder bridge on MSM6295

I removed the bridge and sound was fully restored as well as board 100% fixed.

 Posted by at 8:51 pm