PCB Repair Logs – Page 111

CPS2 volume fix

Feb 122011

I have been looking for a fault on a CPS2 A board today. There was no volume coming out to the JAMMA connector but there was from the line out connectors (Stereo Q sound).
I couldn’t really find anything wrong as I had proved the on board amp was working.

I entered the test menu and it reported the volume was up full so I started to turn it down, when I got half way down the volume bar disappeared and the volume reported being set at 0. When I started to turn the volume up again the sound was back and it works perfectly.

Not sure what this was all about but its certainly something to keep in mind before I start poking around with a similar fault again.

CPS2 A board repair log

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Feb 052011

Very small repair.
I have finished making up plugs for various kick harnesses which makes it nice and easy to swap out games. I started playing my Street Fighter Zero 2 game and the sound was far too loud, when I tried to enter the test mode I found that none of the buttons on the A board worked.
I opened the case and found that the buttons had seen better days.
The buttons are normal SMD push buttons. The Capcom ones have a fifth leg which is just grounding the case of the push button and the ones I have as replacement one have 3 but since the buttons are activated via plastic switches I’m not too bothered.
Id already replaced the TEST button when I took this picture.

Changed all 3 and tested the board. The volume can now be set to a normal level.

Teenage Mutant Ninja Turtles – Turtles in Time repair log #1

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Feb 012011

Got this TMNT2 board today cheap because it had a fault of slight graphics corruption.
The intro sequence was a bit of a mess and was very responsive moved.

I ran the built in MASKROM tests and 3K and 3L came us a BAD.

As one of the ROMs was socketed I removed it tried to dump it, I got a positive match from ROMIdent. As a little test I powered the board up without the ROM in and ran the test again, this time 3K showed up as BAD (it was removed) but 3L showed as GOOD.
I then corrupted the same ROM file in MAME and ran the MAME version, I had managed to reproduce my fault.

After much probing and head scratching I found that the enable line of ROM 3K must have a break in it under the solder mask of the PCB and was quite intermittent. This line is “active low” and when it goes open circuit (or dead) the chip enables and corrupts the data being sent as both 3K and 3L are sending their data together.
I traced the line back to its source which was pin 8 of a 74ALS04 at location 18F. I have ran a link from here to pin 12 of the ROM and the board now plays perfectly and passes all tests.

Cabal repair log

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Dec 292010

Got a Cabal game. It looks like a bootleg but is pretty good quality. The ROM’s match that of the joystick version which is good because it means I can test it properly.
As it turned out, the joystick controls were completely erratic and all over the place. I took the top board off to give me access to the traces from the edge connector.

There is a small daughter board present which is silkscreened with “Joystic Sub”. I removed this and found the likely cause of the problem, several of the pins had broken off.

I cut the pins out that were broken and replaced them as required. Pins 13 and 14 were not connected to anything so I didn’t bother replacing them.
Fired the game up and the controls are working again. Pretty addictive game too.

Golden Axe repair log #2

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Dec 022010

My Golden Axe (set 1, World, FD1094 317-0110) had suicided.
I have a copy of the decrypted ROMs from Sega Resurrection. I pulled the two EPROMs from locations A1 and A2 on the top board (27C2001), erased and reprogrammed them and also fitted a standard 68k CPU in place of the custom block.
My Golden Axe board is alive once more and now have no worries about that suicide battery anymore.

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