MK t-unit no sound /garbled and random sounds

lvlwitdadevil

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Issue is with MK t-unit. The sound is messed up. I get the initial chime on boot at the rom check screen. After that there is no sound at all. Occasionally there is a garbled / strange beeps/screeches when playing but it is sporadic. On my diagnostic screen the sound IRQ detect is okay, but I get no tones on the test.

Voltage from PS/ 50K pot/ ribbons-cables/ and all game roms are good. I even tried switching out sound roms from a working Y-unit sound board to see if it would fix the problem, but no good. Caps on sound board look fine, all traces look good and I do not see any discoloration or burned components.

Anyone have a similar issue? Unfortunately the Yunit sound board itself can not be used as a replacement because of different components.

Any help would be appreciated, thanks!
 
let me clarify the sound board situation...

Midway released MK with 2 different makes of sound board, you can see this in the MK T-unit manual. either model will work. you can even use the same wiring harness from a Y-unit sound board, the extra pin is just another ground wire, all you have to do is make sure you line up the first pin of the harness connector with pin 1 on the T-unit board. as for the differences between Y-unit and T-unit, I don't know if there is any; I just bought an NBA Jam board that's a T-unit and the sound board on it looks identical to my MK Y-unit one (my MK T-unit board I got did not come with a sound board).

as for your problem, it sounds a bit like the one I had with my MK2 when the sound and game would work fine one second, then throw up Custom Chip UE13 errors and alternate between the Sound IRQ being ok and Sound IRQ not detected, and in both instances it would play random sounds or most notably the Babality crying sound over and over.

I never resolved this problem until I pulled the UJ12 and UG12 roms and saw that there was a shitload of corrosion on the chip legs, and upon sanding them the game worked perfectly fine ever since.
 
All I know is I have a problem with 2 different MK boards. I think it's funny how so many folks are having problems with MK boards at the same time. Just like the CPS-1 boards.
 
Mecha, thanks for the info.

Used the Y-unit sound board (A-14732), and my sound works fine with it.

The T-unit and Y-unit sound boards look identical, but each sound board has different audio/power amps. That and I did notice a discrepancy with my 43725 sound board,

It is missing the Y1 (3.58 mhz crystal)???


Does your NBA Jam sound board have this missing also? Its a silver racetrack like cylinder. If the sound crystal is supposed to be there I think I may have found the problem, that may be why my sound is bad on the t-unit sound board.
 
It is missing the Y1 (3.58 mhz crystal)???


Does your NBA Jam sound board have this missing also? Its a silver racetrack like cylinder. If the sound crystal is supposed to be there I think I may have found the problem, that may be why my sound is bad on the t-unit sound board.

I just checked my NBA Jam TE board set and yes there is a crystal at y1. and it is a T unit.

For more info and pics check out this post

http://forums.arcade-museum.com/showpost.php?p=1438353&postcount=13

and read over this thread started by Mecha187 himself :D

http://forums.arcade-museum.com/showthread.php?t=162002

i've gone back to it a few times.
 
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I just looked at my spare NBA Jam TE board and it's also missing the Y1 crystal. anyone know where i can get one? bob roberts maybe?

Edit: looks like he does, gonna order at least 1
 
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does your sound work with the board missing the crystal? If not then it could be the culprit.
 
mine does not 100%.

the only thing it does is bong/beep 7ish times. and that is it, it does it when i go into the test menu and when the game is playing.

My U3 chip is also mashed up. I just got some y1 crystals from Bob Roberts guess now i just need to get a replacement u3.
 
my t-unit sound board would do the same thing. I would get no sound, but I would get random stuff.

It must be the crystal.
 
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