PCB Repair Logs – Page 30

Psychic 5 repair log #2

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.

Dogyuun repair log #2

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Mar 212018

Got from Portugal another Dogyuun PCB (after the one of some months ago), this was declared as ‘dead’ by the owner :

And it was so.All I got was a steady black screen, no activity on board, no clock on 68000 main CPU.I checked voltages on edge connector and there was no +5V so the board was actually not powered :

A quick inspection revealed corrosion on edge connector:

Once cleaned it the board booted and played fine but sound samples were muffled and some static noise was present :

Some sign of electrolytic capacitor leaking was present on sound section :

I fired up my ESR meter and started measuring capacitors.A couple of them, the 220uF 16V @C7 and the 10uF 16V @C9, gave no reading so out of range of my meter (0-99 Ohm)

I replaced them, this restored clear sound.No other issue were found so board 100% fixed.

Teenage Mutant Hero Turtles repair log #5 and Konami ‘007340’ reproduction

PCB Repair Logs, Reproductions Comments Off

Mar 182018

Got in a trade this untested Teenage Mutant Hero Turtles PCB:

At first test the board turned out to be faulty.Sprites were scrambled and some sound samples scratchy:

I launched a MASK ROM test which reported as bad all four 4Mbit devices storing sprites data:

Obviously the result didn’t mean the MASK ROMs were all bad, this was quite unlikely but for sure there was a problem in the sprites generation circuit.

Most of the circuit is condensed in two ASICs, the ‘051960’ which generates the address for the MASK ROMs and the ‘051937’ which reads their data:

Judging from type of fault, the ‘051960’ was generating wrong address, you can see its implementation in this snippet of schematics :

Also scope analyzing confirmed my suspicions :

This lead me to remove and replace the ASIC:

This restored sprites so the IC was really bad (it’s not the first time, see my past repair log of Block Hole)

Now the sound issue.A quick visual inspection revealed that one of the two components marked ‘007340’ was cracked in two:

As schematics suggest the ‘007340’ is a resistor ladder (R2R) used to convert into analog the digital bits outputted from the ‘007232’ PCM controller so I made a very rough replacement that worked fine:

Later I properly reproduced it :

Another PCB fixed and another (little) custom reproduced.

Gals Panic repair log and Kaneko ‘PX4460’ – ‘LPF6K’ reproduction

PCB Repair Logs, Reproductions 1 Response »

Mar 122018

Picked up recently this cheap untested Gals Panic PCB (MCU protected version)

When powered up I was greeted by this :

All inputs (including SERVICE one) are handled by a custom in SIL package marked ‘MC-8282’ (found also as ‘MC-1091’ in other boards from Kaneko)

I’ve already discussed the topic in my past post about the reproduction of this custom:

Kaneko ‘MC-1091/MC-8282’ reproduction

Most likely the component was internally faulty so I replaced it with a repro of mine:

Finally the board booted into game but the sound was barely audible also at maximum volume level:

After a visual inspection I found that the component silkscreened ‘PX4460’ was missing from sound section:

Board uses also another little sound custom, the “LPF6K”, here is a picture from another board for better understanding:

Actually you can replace them by installing the parts they are internally made of directly on PCB (there is silkscreening for them) but I wanted to keep the all-in-one solution the so I decided to have a look inside them in order to reproduce both (although the ‘LPF6K’ was not missing on my board).I removed the coating and did an Hi-Res scan;

On the left on the above picture it’s the naked ‘PX4460’ which, like its name suggests, embeds all the parts (minus the 1000uF 16V electrolytic capacitor, this is on the PCB) needed by the typical application circuit of the ‘LA4460’ amplifier as datasheet shows :