X-Men Children of the Atom Phoenix error

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Mar 022011
 

I got 2 CPS2 boards today for repair.
One of them was a Children of the Atom game that had suicided, simple enough.
I erased ROMs 3 and 4 and burned the bootleg code. The game booted up to the copyright screen then bombed me out with an error.

After a bit of playing about it turns out that the installed ROMs were from the Japanese version of this game and this is different from the Euro version (which is what the Phoenix ROMs are based on) so I had to erase ROMs 5 – 10 and reprogram them with the Euro version.

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.

CPS2 volume fix

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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.


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