Mortal Kombat 2 - Sound Board repair

orion3311

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Are there any common problems with the MK2 sound boards? I always see posts for dead ones or people wanting working ones. One that I have is dead and I get clicks and pops for sound.

I verified the U2 rom *Was* good...until I put it back in backwards. Now its not so good and some 27c4001s are cooking in the eraser sigh.
 
I haven't finished repairing mine yet, to many other projects going on. I did replace my u2 tho that i like you mistakenly installed backwards >.< (first and last time for this. lesson learned).

Mine makes a faint screeching/scratchy static noise, no popping. (maybe some clicking or tapping tho, here's a vid).

 
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I felt like an idiot until I realized the rom socket does have a notch on the wrong side..thats what threw me off.

Rom burner is not cooperating so I may have to quit for the night.
 
I felt like an idiot until I realized the rom socket does have a notch on the wrong side..thats what threw me off.

Rom burner is not cooperating so I may have to quit for the night.

i mistakenly put mine in the wrong way in a rush to test it or something... just wasn't thinking, i now triple check or more before power up of any board that the chips are in correctly. hopefully in the next month or so i'll get to looking at this again.

That video kinda sucks but you get the idea.
 
Mine's doing the same thing.

Saw a post from back in Nov where someone narrowed it down to possibly the DAC chip and/or the TL084. I'm going to see if I can find them somewhere cheap maybe and see what happens.
 
yea that was action76 i think, not sure if he ever figured out the problem or not. haven't seen him on in a bit.
 
Quick update - It does seem the DAC could be bad, it has input coming in but nothing going out. I guess if I end up getting one we'll see what happens.
 
let me know if the new one changes it and where u got it from, i suppose i could start shotgunning parts. (no logic probe here).
 
Quick update - It does seem the DAC could be bad, it has input coming in but nothing going out. I guess if I end up getting one we'll see what happens.

any luck finding a replacement and any change?
 
If I may interject, the screeching is a somewhat common issue as I have come across many sound boards that work except for that noise.

Now as for the reason I am posting..

I didn't see anyone mention the ribbon cable. I assume it's on correctly and not backwards at either end. This is usually the most common mistake/error. I know it's kind of moot as this point because of your other problems, but could that have been the issue at the beginning?
 
If I may interject, the screeching is a somewhat common issue as I have come across many sound boards that work except for that noise.

Now as for the reason I am posting..

I didn't see anyone mention the ribbon cable. I assume it's on correctly and not backwards at either end. This is usually the most common mistake/error. I know it's kind of moot as this point because of your other problems, but could that have been the issue at the beginning?

would it really matter? There is no KEY to the components so why would the wires be upside down/backwards matter? either way it would be the same wire making the connection
 
I haven't finished repairing mine yet, to many other projects going on. I did replace my u2 tho that i like you mistakenly installed backwards >.< (first and last time for this. lesson learned).

Mine makes a faint screeching/scratchy static noise, no popping. (maybe some clicking or tapping tho, here's a vid).


mine does this exact same thing... I was thinking bad caps... but seems like its just that way it is!!
 
mine does this exact same thing... I was thinking bad caps... but seems like its just that way it is!!

That's what it is... You are hearing the power draws of the system on the +5v line and it's probably bleeding over onto the +12. That isn't a sound board issue, it's a power filtering issue or a funky grounding issue.

It reminds me of the hum you get on a stereo or PA system from a ground loop or ground problem. Sometimes it's a cable problem, other times it's a bad cap somewhere.
 
Mine's doing the same thing.

Saw a post from back in Nov where someone narrowed it down to possibly the DAC chip and/or the TL084. I'm going to see if I can find them somewhere cheap maybe and see what happens.

I think Channelmaniac has some he is looking for, I need one sent to Canada for a Zero Wing pcb with no sound.

Also check that DAC for a clock signal, without the clock it will not work.
 
If I may interject, the screeching is a somewhat common issue as I have come across many sound boards that work except for that noise.

Now as for the reason I am posting..

I didn't see anyone mention the ribbon cable. I assume it's on correctly and not backwards at either end. This is usually the most common mistake/error. I know it's kind of moot as this point because of your other problems, but could that have been the issue at the beginning?

this isn't my first rodeo (translation: nope it was installed correctly), i suppose some people just don't know what that "1" is at the beginning of the ribbon header. the specific soundboard that does this to me makes no other noticeable/recognizable sounds.

mine does this exact same thing... I was thinking bad caps... but seems like its just that way it is!!


i suppose i could replace the caps and xtal on the board before going to the dac, maybe reflow the ribbon header pins as well.... hmm maybe i'll throw some time and caps in it this week and report my findings.


also i've tried this non working board on my 4 other mk2 boards with 0 change, and i've hooked up my working sound board to the same setup with no issues as well which rules out the wiring.
 
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