Mortal Kombat Sound Board Crackling

[xodaraP]

Hi guys,

I have a Mortal Kombat 1 boardset and the sound is crackling.

The sounds are correct and can still be heard as normal under the crackling, I have recapped it by replacing all the electrolytic capacitors with Rubycons but it didn't fix it.

Where is the next step? I was thinking the DAC might be the issue but rather than start shotgunning components I'm wondering if anyone has come across the issue.

I have 3 other sound boards here I can swap parts from if necessary (all are missing some components and ROMs, I'm rebuilding them one by one)

 

[aha2940]

I have no experience with this particular board, but I have had similar sound issues in other platforms, and it usually is one of these:

- Cold/bad solders in one (or more) component
- Bad connection in a cable/broken cable
- Corrupted roms (verify against MAME set)
- DAC gone bad

Regards.

 

[Mitsurugi-w]

At this stage in their life I would just go ahead and change the ribbon cables to start. They are getting brittle by now and remember how thin those conductors are in there.

 

[xodaraP]

At this stage in their life I would just go ahead and change the ribbon cables to start. They are getting brittle by now and remember how thin those conductors are in there.

Good point. I'll see if I can track them down. From memory it's the same as a 3.5" FDD

 

[Trol]

Had the exact same issue, I replaced the Oki surface mount chip to fix it.

 

[xodaraP]

Yeah that's the DAC, fairly sure it's through hole on the MK1 board and then SMD on the DCS boardset for MK2 - I'll try replacing the ribbon cable first and if that doesn't help the DAC is my next port of call

 

[MortalkombatGod]

Hi XodaraP

How did you go with this repair? I have the same crackling issue atm with my NBA Jam. I've gone through every thing like caps, cables, rom checks even swapped it out with another sound board which works fine with the game board. At this point im leaning towards the OKI (DAC)

 

[xodaraP]

My issue was the volume pot was incorrect. Once I installed a 50k pot the sound was perfect

Your volume pot might be bad but if you're using the same one on the other audio board then it could well be the amp or DAC

 

[MortalkombatGod]

Hey mate yeah i used the same pot on the other working board and the pot was fine as for the amp i tried a new one but same issue. i might replace the DAC and go from there.