Mortal Kombat 3 Sound Issues

riddler

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Hello,
I have a dedicated MK3 cabinet that I am having issues with the sounds. I get nothing. Everything else seems to work perfect. This is what I have done so far. I checked all the voltages at the jamma connector. I have +5.09, -5.10, and +12.13. I have checked continuity from the speakers to the jamma connector. When it boots up it runs through the rom tests with no errors and automatically boots to the game when done. I hit the test button and go through the sound board test and nothing is highlighted. I get no sound. I have adjusted the volume on screen to about 3/4 of the way up. I just replaced the sound amp todayTDA7240A and still no sound.
I am at my wits end with this game. Any suggestions where should I go from here. I am only a novice at arcade repair and I might be missing something really stupid.
 
Do you get the initial "Bong" when you boot the machine? If not, your sound processor is not functioning due to either being bad, or some other external input to it not being received by it. Does the burn in test show it as good? Does it come up green? Do you get any kind of error when you boot the board?

If not, I'd be 50/50 on if it's a board issue or a cab issue. Plug in another Jamma board to your cab and if the sound works, then you have an issue with the MK3 board. If that proves true, my money'd be on the sound processor crapping out or something else on the board is affecting it's operation.
 
besides what Zeno said, have you tried the board in another cabinet just to confirm it's a board issue? (or another jamma board in this cabinet)
 
Thank you both for the info. I am not getting the bong in the beginning or any sounds at all. As far as I know the burn in test is all good because it says checking and I see the roms turning green and then it quickly flashes to the main game screen. I am not sure what numbers the sound roms are because most of the papers that cover the windows have fallen off. I put electrical tape over the windows so I do not let any light in. I do not receive any kind of errors when booting up.
I will have to try another jamma board in this cabinet and also try this MK3 board in a different cabinet.
Thank you both again for your help. I will probably be able to try this tomorrow or Monday. I will let you know how it turns out.
 
You're welcome and keep us informed. It's odd because if your sound processor was bad or not working because of a missing input, then it should come up red and the game would say something like "Sound Section Timed Out."
 
This is where you need an oscilloscope to check the outputs of the sound chip and to check the op-amps in the analog sound amp section.

Also, look for chips with cracks in them or heat damage. The next thing is to check the pesky little surface mount RFI filter coils as they tend to go open. They are the dark grey ferrite ones that are the same shape as the tiny surface mount caps. The difference is that they run almost zero ohms when you check with an ohmmeter.
 
I have been working on this issue last night and tonight. My other Jamma cabinet has a sound issue as well and I am trying to resolve that issue so I can test my board in another cabinet. My other cabinet has Rastan with no sound. I had another Rastan board with no roms on it so I put all the roms from the board with no sound and still no sound on the other board. I have tried adjusting the pot. I do not have any other working Jamma boards at the time to test to make sure my Rastan cab has sound. I have put my Ultimate MK3 board into the Rastan cab and no sound and no error messages after the rom test. I will post back when I can get all this mess worked out or get a little bit more info.
 
thanks for the update. let us know how you make out.

be sure and check the wiring to the volume pot and to the speakers and from the board to either/both (pins 10 and L are the + and - to the speakers on a jamma harness)
 
I have found another Jamma board Time Soldiers and have tried that in My Ultimate MK3 cab and it has no sound and the screen is scrambled like a sync issue but can make out the character playing. When I try Time Soldiers in my Rastan cabinet it has sound and the screen is normal. So it sounds like maybe I am having a problem with the cabinet and the board with the sound issue. I have also checked the board for chips with cracks or heat damage and could not find any. I checked the RFI Filter Coils I believe 3 of them and they all measure .02 ohms in circuit. Since I do not have a oscilliscope and do not know how to use one I might be at the stage where I need to send it in for repair. I bought the game recently and was told that everything worked except the monitor was a little wavy at times. I could not power the game before buying because the power had been shut off at the business. When I got it home the monitor was wavy all the time and there was no sound. I have gotten the monitor issue resolved and just have this sound issue looming. Any other suggestions I might try or does anybody know somebody that can fix this board cheaply. I am hoping to resell this game and hopefully I will not be too upside down in it.
 
Anybody have any idea where I can go from here? Or does anybody know who can repair the sound on this board?
 
Channelmaniac there's always a possibility that it can't be fixed but he took good care of a couple of my broken boards
 
I just wanted to give an update on this sound issue. I just got it fixed after about 20 hours of messing with this game. I used my meter and ohmed out the speakers and both were bad. A 3rd test speaker that I had plugged into it earlier was bad as well. The fourth speaker I tried tested good but was held together with tape. I used this speaker to test and sure enough I have sound a little buzzy due to the tape on the speaker but hey I got sound. Time to buy some speakers and some extras so when I use a spare to test, it actually works.
Thanks again to all that helped with this issue.
 
I just wanted to give an update on this sound issue. I just got it fixed after about 20 hours of messing with this game. I used my meter and ohmed out the speakers and both were bad. A 3rd test speaker that I had plugged into it earlier was bad as well. The fourth speaker I tried tested good but was held together with tape. I used this speaker to test and sure enough I have sound a little buzzy due to the tape on the speaker but hey I got sound. Time to buy some speakers and some extras so when I use a spare to test, it actually works.
Thanks again to all that helped with this issue.

hah awesome great to hear, funny sometimes it can be the simple things (usually is).
 
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