Double Dragon repair log #3

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Feb 282011
 

Bought this a little while back as spares or repair. The fault was it had no sound but due to my scope packing in I never got around to fixing it until now.
The board is in outstanding condition and very clean.
I pulled out the schematics for this board that I had stashed away and began working my way backwards from the amp.
I found the analog output from the YM3012 was dead, replacing this chip brought back the music but some of the sound effects were still missing, namely the attack sounds. I recreated the fault using MAME by corrupting the ADPCM ROM 21j-6. From here I could trace the fault from the ROM right through to the amp.
I traced the fault to IC80, M5205 (ADPCM Speech Synthesis LSI). I could see the data going into it but pin 10 (output) was silent. Replacing this brought back the effects and completed the repair.

Nintendo Super System

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Feb 242011
 

I have got hold of a very nice Nintendo Super System. This was the arcade equivalent of the Super Nintendo. The board is in very good condition but was sold on eBay as “untested” which usually means it doesn’t work.

The board came with 3 games, Super Mario World, Super Soccer and Super Tennis. From what I can tell all these games are the same as the SNES versions with the addition of the game timer.

It came today and I fired it up, it uses a standard JAMMA pinout with a couple of extra things and stereo sound instead of mono.
Much to my surprise the board boots up and everything plays fine.


Its an interesting piece of hardware but not sure why it was ever made as it was released around the same time as the SNES was.

CP System 1.5 (Dash) – Cadillacs and Dinosaurs

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Feb 162011
 

Got my first CPS Dash game today.
Its Cadillacs and Dinosaurs and has been modded so as not to suicide.

It looked like a conversion as the label is not the proper one and there is a genuine Slam Masters sticker underneath it (which I have removed and scanned) but inside all of the MASKROMs are genuine Capcom Cadillacs ones so looks like the case might be a donor.

The CPS Dash games are middle ground from the CPS1 and CPS2 boards. They have a case, it has a built in fan, Q-Sound is used and there is separate line out audio.
The boards are similar to that of CPS1 but the A board has been stripped of its audio section and this is now located on a new B board which has the Q-Sound chips and in this case, a suicide battery that when it dies it takes the sounds with it.

The C board on this is what has all the game ROM’s on it and the small D board is what is the C board on the CPS1 games. This D board also had a suicide battery on it. Phew!

No suicide mod

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.


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