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:
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.
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.
PCB Repair Logs, ReproductionsComments Off on Teenage Mutant Hero Turtles repair log #5 and Konami ‘007340’ reproduction
Mar182018
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.
