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Donkey Kong 3 repair log

Nov 042017

Got a Donkey Kong 3 to repair from my good friend Alex @ Nintendo Arcade
On boot up I got a static green of garbage

I checked the voltages at the far end of the PCB and saw they were quite low compared to what my PSU was set at. Adjusting the voltage to a bit higher brought the PCB voltage back up to a good point but made no difference to the fault.
Next job was to check the program ROM’s

Found 7C, 7D & 7E had suffered from bit rot. I erased these and reprogrammed them with the correct data from the MAME set.
It didn’t make any difference at all so I started looking at the Z80 CPU signals and this is where I got a little confused.

At first glance and without really engaging brain too much I automatically assumed that there were two Z80 CPU’s side by side but checking the voltages and the signals left me scratching my head as they were not what I had thought. On closer inspection I realised that the one on the left is actually a Z80 DMA chip. I’ve not seen or even heard of these before so it something new to me.
I took to the internet and downloaded the datasheet for the DMA chip and also the schematics for this PCB too.
The CPU and the DMA chip are tied to the same busses and the DMA chip didn’t appear to be releasing the data bus to allow the CPU to do its thing.
I checked all the incoming signals to the DMA chip but found nothing odd so at this point I figured I needed to buy a new DMA chip so ordered one from eBay.
To help confirm my diagnosis I pulled the DMA chip and powered up the game. Sure enough it booted fine and ran but was missing the sprites which is to be expected really.

A couple of days later I received the new chip and now we get this

All sound and controls working too so that’s this one sorted.
There appears to be some skewing at points in the pictures above. This is due to my supergun setup and not a PCB fault.

Super Burger Time repair log

PCB Repair Logs 1 Response »

Nov 012017

Got this Super Burger Time PCB (by Data East) for a repair:

Board played fine except for the fact the BLUE color was totally missing hence the yellowish screen:

Palette RAMs are two 2K x 8-bit devices, both were Sony CXK5814 (6116 compatible) which are well known to be unreliable:

Probing them revealed that the one @9K had all data lines stuck low while address were happily toggling (on left of the below picture)

The IC was most likely bad so I removed it:

The out-of-circuit confirmed it:

Replacing it fixed the board completely.

Super Burger Time PAL dumps converted and tested.Pang 3 and Knight of Valour Super Heroes PAL dumps added

PAL Updates Comments Off

Nov 012017

Another PALs update today.

I have converted to GAL16V8 fuse map the Super Burger Time PAL dumps we had from Luiskiko time ago, they all works fine when tested.

‘cpsystem3’ sent in dump (successfully tested by himself) of the PLD present on a Knight of Valour Super Heroes PGM cartridge, thanks to him.

Lastly, I dumped the PLD @1F from what appears to be a well made reproduction of Pang 3 B-BOARD

Equations of PAL are different from original board since bootleg use eight 4Mbit GFX ROMs instead of the two 16Mbit ones of genuine boardl.All other PALs are identical to original.Dump is untested for now since board is not working.

Big PAL dumps update

PAL Updates Comments Off

Oct 292017

Today we have a massive update.Dumps came from the following PCBs:

Athena bootleg

Porchy dumped the PALs from a copy board and successfully tested dumps back on board.Corrado Tomaselli confirmed dumps are working also on the original PCB.Devices were all unsecured (two PAL16L8 and one PAL20L8) and they have been reversed into GAL devices (for the 24 pin one both GAL20V8 and GAL22V10 replacement available).Thanks again to both them.

Cyberball (prototype with serial #0002)

Dumps were provided by ‘coolmod’ on Dumping Union list from an early revision/protoype of board.Devices were all unsecured PAL16L8.We mark them as “assumed working” since we have no means of testing GAL replacements.Thanks to him.

Locked ‘n Loaded

256KB binary PAL dumps provided by Smitdogg on Dumping Union from a faulty board.I reversed them into GAL fuse map which we mark as ‘untested’ until testing on a working PCB will be done.Thanks to him.

Gokidetor (a mechanical wack a mole type game by Taito)

Dumps provided by Smitdogg on Dumping Union, devices were all unsecured.We mark them as “assumed working” for now.Thanks to him.

Bobble Bobble (bootleg of Bubble Bobble)

I dumped and reversed into GALs the three PALs from this one layer bootleg.All dumps matches the two layer version (dumped by Porchy some time ago) except for one which has slightly different equations.

Tecmo World Cup ’94

Board has six PALs but I was able to dump and reverse into GAL only the one @U64.

Pipe Dream

I dumped the PLDs from a dead board.Out of four devices present one was registered so not dumpable.Dumps are untested for now until we can test them on a working board.

CPS1 ‘DASH’ A-BOARD repair log

PCB Repair Logs 2 Responses »

Oct 252017

Received this faulty Capcom CPS1 A-BOARD, actually the ‘DASH’ revision with a 12MHz oscillator in place of 10MHz one:

Board played with good graphics but sound samples were completely wrong and randomly played, here’s a video made with a Captain Commando B-BOARD/C-BOARD:

PCM samples are played by an OKI ‘MSM6295’ IC which addresses two 1Mbit devices (located on B-BOARD) and reads back their data.Judging from flux residuals the IC was previously reworked on this board as well as other components of audio circuit:

For first I tested all traces to/from it, all was OK.So, most likely, the IC was bad, no wonder since it’s a prone to failure part.I removed it:

Cleaned the PCB from flux and installed the spare:

Time to test:

Board fixed.End of job.

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