Mortal Kombat 1 Audio Amp Help

Tighe

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May 25, 2009
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Location
Richmondville, New York
Symptom:
Audio is weak and almost unamplified.

What I did:
I replaced all the electrolytic caps (with nichicon and panasonic brand) on my MK1 sound board. found that c87, c79, and c83 had leaked.

The problem is still there. I see no other visible problems. I didn't replace any of the axial caps. Do they go bad like electolytic?

Do you think I should replace the MOSFET (U31) on the board?

EDIT:
I ended up ordering it:
http://www.electronica-usa.com/Merc...re_Code=EU&Product_Code=HA13118&Category_Code
 
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Wish i could have been more help, hope the amplifier chip rectifies the problem.
 
listen for amplifier hiss. if it's not present, your amp is just dead. I would think the speakers would still work without it, it'd just be extremely quiet like you say.

good news is that hiss isn't hard to detect on Williams/Midway hardware, they're generally pretty obnoxious in that department. lol

EDIT: I was telling Broods that I have some of those sound boards that don't have the plastic pins that go between the amp heatsink and the board, and that the pins on those are probably very easy to break from flexing if that pin isn't present. oh also, an axial cap is also electrolytic. axial is just the form factor of the cap, like the 2 legs sticking out the bottom being radial. I doubt that's what the problem is though... leaning more towards the amp.
 
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listen for amplifier hiss. if it's not present, your amp is just dead. I would think the speakers would still work without it, it'd just be extremely quiet like you say.

good news is that hiss isn't hard to detect on Williams/Midway hardware, they're generally pretty obnoxious in that department. lol

EDIT: I was telling Broods that I have some of those sound boards that don't have the plastic pins that go between the amp heatsink and the board, and that the pins on those are probably very easy to break from flexing if that pin isn't present. oh also, an axial cap is also electrolytic. axial is just the form factor of the cap, like the 2 legs sticking out the bottom being radial. I doubt that's what the problem is though... leaning more towards the amp.

Thanks! Acutally the sound is pretty hissy and quiet. My heat sink has the plastic peg. All the pins look good too.

You can see it in the right of this photo, also you can one of the leaky caps:

IMG_20111021_010955.jpg


IMG_20111021_004256.jpg
 
maybe it's just me or the picture, but a lot of those solder joints look kinda bad.

if the new amp doesn't take care of it, I'd start reflowing like.... a lot of stuff.

also make sure that leaky cap didn't spread everywhere. that's what kills those X-Men and other Konami boards you know. lol
 
maybe it's just me or the picture, but a lot of those solder joints look kinda bad.

if the new amp doesn't take care of it, I'd start reflowing like.... a lot of stuff.

also make sure that leaky cap didn't spread everywhere. that's what kills those X-Men and other Konami boards you know. lol

I think it is the photo, they looked fine in person.
 
Follow-up

So this morning I tried out a extra sound board that Broodwich gave me (what a swell guy) and I was having the same problem. I quickly determined that the problem was actually the pin inside the volume pot molex connector.

What happened is that the wire broke at the connector crimp, but the wire insulation was still crimped. The wire still made contact so that it showed with a continuity test. I jumped the to contacts on the pot expecting to get full volume but didn't I never tried it directly on the header pins. When it didn't work this morning I did that got full volume, then I pulled the pins from the molex and found the short. Woops. Well at least I have a nicely rebuilt MK sound board now.
 
So this morning I tried out a extra sound board that Broodwich gave me (what a swell guy) and I was having the same problem. I quickly determined that the problem was actually the pin inside the volume pot molex connector.

What happened is that the wire broke at the connector crimp, but the wire insulation was still crimped. The wire still made contact so that it showed with a continuity test. I jumped the to contacts on the pot expecting to get full volume but didn't I never tried it directly on the header pins. When it didn't work this morning I did that got full volume, then I pulled the pins from the molex and found the short. Woops. Well at least I have a nicely rebuilt MK sound board now.

and soon you will have a nicely crimped volume pot connector :D i just need to buy a cap kit or two so we can put caps in the wrong spot.

edit: or you could remove the volume pot from your machine and stop over one day to check out the progress on KI while i repair your connector.
 
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and soon you will have a nicely crimped volume pot connector :D i just need to buy a cap kit or two so we can put caps in the wrong spot.

edit: or you could remove the volume pot from your machine and stop over one day to check out the progress on KI while i repair your connector.

I already repaired the connector, I just striped the wire and soldered to the connector and reinserted. :D
 
Symptom:
Audio is weak and almost unamplified.

What I did:
I replaced all the electrolytic caps (with nichicon and panasonic brand) on my MK1 sound board. found that c87, c79, and c83 had leaked.

The problem is still there. I see no other visible problems. I didn't replace any of the axial caps. Do they go bad like electolytic?

Do you think I should replace the MOSFET (U31) [HA13118] on the board?

EDIT:
I ended up ordering it:
http://www.electronica-usa.com/Merc...re_Code=EU&Product_Code=HA13118&Category_Code

EDIT 2:
The link was broken, here is an updated one:
http://www.electronica-usa.com/product_HA13118.html
 
all i said was there's no pad left for solder to stick to.

your the one crying about how bad it looks. I cleaned it up a little that's all (not that it matters lol)

I threw in the towel on that thing, not worth the time to recap those axial caps (atleast not taking them from another board). these boards can be found cheap if you look in the right places.
 
all i said was there's no pad left for solder to stick to.

your the one crying about how bad it looks. I cleaned it up a little that's all (not that it matters lol)

I threw in the towel on that thing, not worth the time to recap those axial caps (atleast not taking them from another board). these boards can be found cheap if you look in the right places.

41090788.happyguy.jpg
 
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