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Taito ‘PC040DA’ reproduction

Reproductions Comments Off

Apr 162018

The ‘PC040DA’ is RGB DAC (Digital to Analog Converter) used on some Taito PCBs from mid 80s like Rastan, Operation Wolf, Tokio, LSA Squad.As other similar color DAC it comes in SIL package:

But, as you can see from picture above, unlike the “big brother” ‘TC0070RGB’, you will always find three ‘PC040DA’ (one for each color) on a same PCB.Technically speaking the custom is a 5-bit DAC (6-bit actually but the least significant bit is tied to GROUND or VCC ) for a total of 15-bit of palette data received on their inputs.You can see its pinout in this snippet of Bubble Bobble schematics:

This custom has been already analized and successfully reproduced some years ago, you can read more about on this french forums :

https://www.gamoover.net/Forums/index.php?topic=27336.0

But I decided to do my own reproduction taking inspiration from some bootleg boards where the component has been re-engineered with a simpified circuit.The prototype on breadboard worked fine:

So I developed a proper PCB:

This is the final testing on a Rastan PCB where the reproduction has replaced the original part related to RED color channel:

See you all to my next reproduction project!

Teenage Mutant Hero Turtles repair log #6

PCB Repair Logs Comments Off

Apr 152018

Received a box of faulty PCBs to repair from USA.I started my work on them with this Teenage Mutant Hero Turtles by Konami:

PCB was in very good state and played fine with correct sound too but it had a color issue, the screen was yellowish simptom that the BLUE color was missing:

BLUE, as well as RED and GREEN, is generated by a custom SIL marked ‘052535’ (basically an R2R resistor ladder which acts as DAC , see my reproduction post here for more details)

Probing the custom revealed activity on all inputs (pin 2-3-4-5-6-7 ) but output pin 8 was stuck low:

So the component was internally faulty.I replaced it with same part taken from a spare board :

This restored the missing color.End of job.

Black Tiger repair log #2

PCB Repair Logs Comments Off

Apr 142018

Got a Black Tiger for a repair which had a colour problem on some graphics

It lacked some shades of colour

I decided to look around the palette rams @6C and 6D until I found a fixed address line

Tracing back I found an 74ls157 @5D with an output stuck low.

After checking the inputs I found one of them stuck low and according to its truth table, the output is always low.

Tracing back I found a 74ls273 witth Q3 output low and D3 input oscillating.

Piggybacking a good one restored the correct colours.

After changing it , the game was completely fixed

Xexex repair log #2

PCB Repair Logs Comments Off

Apr 132018

Received from France this mint Xexex PCB:

The board was bought from Japan as working but when arrived there was a noticeable sound issue, a loud buzzing noise present also at lowest volume level :

Obviously the culprit was the ‘054544’ audio module.Electrolytic capacitors on it were already replaced but this was not enough :

Most likely the probem was on the underneath of the module so I removed it and installed sockets:

There was some corrosion on underneath but nothing really serious:

I decided to test the module on an X-Men PCB and it worked fine, audio was clean:

The technical reason why it worked is that X-Men doesn’t use the pre-amplification circuit of the module (a LM358 OP-AMP is present externally on PCB) while Xexex does.So the problem was the 4558 OP-AMP on underneath of the module.I removed it and replaced with an LM358:

The buzzing noise was cut out:

Lastly I painted the module to finish the job:

Psychic 5 repair log #2

PCB Repair Logs, Repair Logs Comments Off

Apr 102018

My beloved original pcb developed once again problems after the last repair log you can read here:

Psychic 5 repair log #1

This time, the overall colour palette was pinked and all text was missing

After some troubleshooting I found again a problem with a Fujitsu ttl 74ls08, same type and week/year of manufacturing of the one I changed on the old repair log!

After changing it, the game worked fine for some minutes and then it developed a new problem

Game lost sync and became bluish

Again I decided to concentrate on the only Fujitsu 74ls08 ttls which were present on the board until I found the faulty one.

Same week/year of manufacturing and same fault: dead outputs

In addition, I found another couple of Fujitsu 74ls08 which had dead outputs and I decided to change all of them with good ones.

Now the game is 100% fixed but there are 3 more Fujitsu ttl waiting to be replaced. I ran out of parts otherwise I would have changed them immediately.

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