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.

Super Street Fighter 2: The New Challengers repair log

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Nov 092010
 

As with the 1944 board, this came from the same seller with the same fault of a solid blue screen.

and like the 1944 board also was that the battery still had 3.6v present, the difference being was that the CPS2 suicide test EPROM didnt work with this indicating that the decryption code was still present in the memory. It is possible for the decryption code to get corrupt and with no other signs of fault I took the plunge and removed the battery, this time thought I discharged the capacitor next to the battery to make certain that the RAM with the decryption code in lost all power. The suicide test EPROM now worked.
After burning 5 new 27C4096 EPROMs for sockets 3 to 7 I fired it up and all is well again.

1944: The Loop Masters repair log

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Nov 092010
 

Bought 2 boards off ebay the other day, one was Super Street Fighter 2 The New Challengers and the other was this 1944 The Loop Masters.
Both were sold as being faulty.
When I fired this up it gave a solid blue screen.

This is a classic sign that the board has suicided so to make sure I opened it up and inserted my CPS2 test eprom (available from CPS2SHOCK site) into ROM slot number 3.
It loaded up confirming that the board had suicided.
The strange thing was that the battery was still giving out 3.6v but as this was one of two board with the same indicated fault I assume the previous owner had done something silly.
Only the EPROM in slot 3 requires replacing to phoenix this game so with that done and the battery removed I fired it up again.


I would have liked to keep it original but there is nothing I can do about that now.

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