MK1 Sound Issue

Tighe

Well-known member
Joined
May 25, 2009
Messages
20,797
Reaction score
825
Location
Richmondville, New York
In know that MK boards can have sound issues, mine just started doing this:

When I turned it on it seemed like there was no sound at all, but after I turned up the volume all the way I could just barely hear it. I tried two other speakers and it sill sounds very quiet.

This harness has two volume controls on off the sound board, and another next to the coin counter.

Any suggestions?
 
I'd say eliminate the coin door one, the sound board one itself HAS to be there, the coin door one is most likely tapped into the JAMMA sound wiring. IMO, I'd disconnect those and splice it back together just to eliminate that coin door one completely. your sound board one should be long enough to reach the coin door pot's mounting bracket, so just rig that up in there instead. :) this way you're not trying to fight 2 separate volume pots (like I do on my 33" showcase, like an idiot)

as for your other problem, I don't know, maybe your amplifier chip went kaput. perhaps bad caps too. you got access to another one to try in there or no?
 
I'd say eliminate the coin door one, the sound board one itself HAS to be there, the coin door one is most likely tapped into the JAMMA sound wiring. IMO, I'd disconnect those and splice it back together just to eliminate that coin door one completely. your sound board one should be long enough to reach the coin door pot's mounting bracket, so just rig that up in there instead. :) this way you're not trying to fight 2 separate volume pots (like I do on my 33" showcase, like an idiot)

as for your other problem, I don't know, maybe your amplifier chip went kaput. perhaps bad caps too. you got access to another one to try in there or no?

I figure it is bad caps in it, I need to pull it and find out v and f so I can order replacements. It seems like every electrolytic capacitor goes bad these days. I am tempted to start a business that manufactures capacitors that are guaranteed to last 20+ years.

The coin door pot is wired weird, like it is stereo (only 1 speaker), how do I bypass?
 
The cabinet mounted sound pot shouldn't need to be bypassed, that's how mine is in my Spider-Man cab, just make sure 1 isn't down all the way lol. I don't bypass mine and just leave my bob roberts pot just dangle'n / hanging around.

I got a bunch of MK boards today including 3 mk1's with 2 sound boards (1 mk1 is a bootleg and has no sound board (thanks to the other members for helping me id that)). One of the sound boards was visually missing the crystal at y1 so i didn't do anything with that until i put a new one in (that one now works perfectly).

The 2nd sound board on the other hand has an issue i can't visually see. The board is mint/clean and no legs on the solder side seem to be touching (tho i can see a tiny hair line between a few of the legs which looks like a mfg. defect). Yet i get nothing more than some crackles and pops out of it, and very randomly.

video here:


ok don'e going Re-animator on this thread.

Hi Tighe!!!!
 
The cabinet mounted sound pot shouldn't need to be bypassed, that's how mine is in my Spider-Man cab, just make sure 1 isn't down all the way lol. I don't bypass mine and just leave my bob roberts pot just dangle'n / hanging around.

I got a bunch of MK boards today including 3 mk1's with 2 sound boards (1 mk1 is a bootleg and has no sound board (thanks to the other members for helping me id that)). One of the sound boards was visually missing the crystal at y1 so i didn't do anything with that until i put a new one in (that one now works perfectly).

The 2nd sound board on the other hand has an issue i can't visually see. The board is mint/clean and no legs on the solder side seem to be touching (tho i can see a tiny hair line between a few of the legs which looks like a mfg. defect). Yet i get nothing more than some crackles and pops out of it, and very randomly.

video here:


ok don'e going Re-animator on this thread.

Hi Tighe!!!!

Yah yah! I need to cap the board, I have all the caps sitting on my workbench. BTW I capped the audio amp on my DK last night, and it still sounds like a banjo, just louder.

http://forums.arcade-museum.com/showthread.php?p=1797330#post1797330

There aren't many parts left to change on the amp board, 1 diode 2 transistors and a bunch of resistors.
 
This wasn't another attempt to get you to work on this :D just figured i'd see if there was any similarity between your issue and mine. I might just stick this in the parts pile as MK1/NBA Jam sound boards are fairly cheap and easy to come by.

Hope you figure your DK out, these damn sound boards are pesky lil bastards.
 
"One of the sound boards was visually missing the crystal at y1 so i didn't do anything with that until i put a new one in (that one now works perfectly)."

If you don't mind me asking. Where did you get that Y1 crystal? Mine is messed up and can't find it ANYWHERE! I have looked on ebay and other websites but always come up short. =(

Thanks
 
Bob Roberts has a mess of crystals. I don't know any numbers off them though.

+1 to this i bought 4 of them from bob, then another member hit me up with a bunch of shorty ones. I'm getting low myself (if your still having trouble finding them or can't order from bob PM me).

Btw the soundboard in that vid is now fixed, fixed it last night. Pretty sure it was the big cap by the amp heatsink that wasn't making a good connection to the board.
 
I would have tried a new pot myself. Your symptom sounds like what happens when there is not a pot installed. If the pot went bad, this is what would happen, in my opinion.
 
I would have tried a new pot myself. Your symptom sounds like what happens when there is not a pot installed. If the pot went bad, this is what would happen, in my opinion.

this pot was from my NBA Jam TE and i had just used it to test/troubleshoot a smash tv board. i jiggled the wires to the pot a good amount and got no change. I'm not 100% shooting down the pot but seems more like it was the cap.
 
I had a similar issue when using an MK1 pot on an NBA JAm resto, as soon as i disconnected it the sound worked perfectly. Something is screwy with the cross over of the pots.
 
MK1 requires a 50K ohm pot. NBA Jam should be the same as the NBA Jam and MK1 (T-Unit) sound boards are interchangeable.
 
MK1 requires a 50K ohm pot. NBA Jam should be the same as the NBA Jam and MK1 (T-Unit) sound boards are interchangeable.

yup yup, correct, NBA Jam/TE, MK1 (both t and y unit), Smash TV, and that football game mecha loves (sorry mecha i can't remember the name of it right now lol) all use the same 50k volume pot, i think smash tv and the football game just require the 3rd wire (shield) to be hooked up also.

I need to get my hands on a T unit board set, that's the only thing i'm missing from my collection right now (since i guess i'm now not only collecting all of 1-u3 but also the different revisions... lol funny how this hobby is).
 
Last edited:
I need to get my hands on a T unit board set, that's the only thing i'm missing from my collection right now (since i guess i'm now not only collecting all of 1-u3 but also the different revisions... lol funny how this hobby is).


I have 2 or 3 extras, but I bought them while here in Afghanistan and haven't tested them yet. They are sitting in boxes waiting for me to go through them when I get back. I bought around 12 PCBs on Ebay during down time over here because I plan on getting all the MK cabs again and putting a 6-in-1 switcher in all of them with all original hardware with all the major revisions of all the games. Make sense?

Anyway, I may end up with an extra one and you're welcome to it for a small fee if you want. Around Oct 18, shoot me a message and I'll let you know if I end up with an extra that I can send you.
 
yup yup, correct, NBA Jam/TE, MK1 (both t and y unit), Smash TV, and that football game mecha loves (sorry mecha i can't remember the name of it right now lol) all use the same 50k volume pot, i think smash tv and the football game just require the 3rd wire (shield) to be hooked up also.

I need to get my hands on a T unit board set, that's the only thing i'm missing from my collection right now (since i guess i'm now not only collecting all of 1-u3 but also the different revisions... lol funny how this hobby is).

the almighty High Impact Football. :) game is so awesome... fuck Blitz, and that stupid John Elway Quarterback.
 
the almighty High Impact Football. :) game is so awesome... fuck Blitz, and that stupid John Elway Quarterback.


yea that game :D

btw Mecha i just fixed another MK1 mainboard, a bunch of solder legs were touching traces on the board and 1 or 2 were actually touching other legs. When i first tested it a large bank of roms were bad and it would lock up at the test menu (not to mention the text on the test menu was all block style and weird looking). It's been a good weekend.

btw grats tighe on fixing your dk cabaret audio! sorry for jacking your thread a lil :D

Edit: oh and wally world has Mortal Kombat T shirts for $7, I fixed that board wearing it tonight lul.
 
Last edited:
yea that game :D

btw Mecha i just fixed another MK1 mainboard, a bunch of solder legs were touching traces on the board and 1 or 2 were actually touching other legs. When i first tested it a large bank of roms were bad and it would lock up at the test menu (not to mention the text on the test menu was all block style and weird looking). It's been a good weekend.

btw grats tighe on fixing your dk cabaret audio! sorry for jacking your thread a lil :D

Edit: oh and wally world has Mortal Kombat T shirts for $7, I fixed that board wearing it tonight lul.

Y-unit or T-unit? block text apparently is caused by the rom region on Y-unit... T-unit I've seen it at the PLCC chip on the left of the board. these idiots that handle these boards need to stop laying them flat without the feet. or WMS should've actually trimmed the pins properly, they're way too god damn long and need I mention extremely sharp.
 
Y unit, I really wish i took a pic/video of what it was doing first before i fixed it. Took me about 1-2 hours to go over every leg on the solder side. Honestly i've had boards with some bent legs but something just didn't seem right and that's why i attacked it in the first place.

I actually pulled my multi meter out to check and see if a couple legs were touching and 1 of the 2 sets definitely had continuity. this board had the plastic washer feet/legs still on the board i swear someone must have stepped on this to do it tho as a lot of the legs weren't damaged.
 
Back
Top Bottom