UMK3 loud static noises

treborlicec

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Hi all. I have a UMK3 PCB that was having graphical glitches and a bad U113 was replaced and all was happy for a few weeks. Now I'm getting an almost constant loud static garbage noise through the speakers. All roms test OK. I've tried pressing on the sound roms and u57(i think), the small sound chip and no change. I've also checked the solder side for any touching pins and not seeing anything.

Any ideas?

Thanks,
Robert
 
loud static noises... sounds a lot like missing -5V to me ;)

check your power supply, make sure it's outputting -5V, on a screw terminal setup it will obviously be the -5V lug, and on the ATX box style with molex plug, it'll be the white #8 wire below the row of black ground wires. (I'm not sure what MK3/UMK3 shipped with or if your unit was replaced previously). if you have it there, then check it at the JAMMA edge, this wire color varies, especially if it's a dedicated machine... so you'll probably have to look up a JAMMA pinout to find which wire it is.

if -5V is present, I guess the next approach to take is to make sure there's no broken/gouged traces anywhere on the underside of the board.

hopefully it's something simple.
 
loud static noises... sounds a lot like missing -5V to me ;)

check your power supply, make sure it's outputting -5V, on a screw terminal setup it will obviously be the -5V lug, and on the ATX box style with molex plug, it'll be the white #8 wire below the row of black ground wires. (I'm not sure what MK3/UMK3 shipped with or if your unit was replaced previously). if you have it there, then check it at the JAMMA edge, this wire color varies, especially if it's a dedicated machine... so you'll probably have to look up a JAMMA pinout to find which wire it is.

if -5V is present, I guess the next approach to take is to make sure there's no broken/gouged traces anywhere on the underside of the board.

hopefully it's something simple.

I have not measured it, but I'm fairly certain -5 is good. My MK3 and MKII boards work fine in here. This is my dedicated MK3 cab. I have a 2 in 1 switcher in it. While on the switcher the UMK3 makes loud static. Switch to MKII by pressing both start buttons, no static. I bypassed the switcher directly to the UMK3 and the same issue, loud static. I'll check the underside again. I just got the dang graphics glitch fixed on it.

Thanks,
Robert
 
if the other games work fine with it then your power supply is fine. is the same slot/spot on the switcher (is this the Clay Cowgill variety?) suspect, or does the UMK3 board do it on both sides?
 
Not Clay's switcher. Works the same on both slots and direct to Jamma.
 
very good. I don't know, verify that the finger for the -5 isn't butchered on the top of the board. that's the best I can come up with, I'm sorry. :/
 
Double verified that there are no pins touching or weirdness on the back. I noticed something I didn't before. I'm not getting any regular game sounds, just static. I can play the game, but only hear static. All roms, even the sound roms show green. Really wish there was more info on these 90's boards available.

Robert
 
Quick update. I found that the only through hole cap on the board had puked. I pulled it, cleaned the area and replaced. No difference. I pulled and reseated the sound IC U57, I believe, and reflowed the solder on the socket. After that, I played a match with no scratchies. Had full sounds, but a medium hum coming from the speakers. Powered down and up again and the static was back. I wish schematics were out there for these boards.
 
these are good signs!!! i don't have any real input on this as you've pretty much hit on everything i would have done. keep up the good work and keep us updated, your getting closer!!!
 
these boards are highly prone to damage from flexing, since there's surface mount components. I don't know how much that will affect the audio, it's mostly the cause for video-related issues, but you never know what the last guy did to the board. :(
 
Swapped all roms and security chip to a spare Wolf unit board and all is fine. Anyone know what value capacitor C10 is on that board? It is too small for me to read. I'm suspecting that. Wanted to see if I could replace with a standard cap and test.
 
Swapped all roms and security chip to a spare Wolf unit board and all is fine. Anyone know what value capacitor C10 is on that board? It is too small for me to read. I'm suspecting that. Wanted to see if I could replace with a standard cap and test.

c10 from what i can read is FL C10u under that..... i can't see to well either and my cam didn't take that great of a pic but it looks like __442 or __642 can't make out the first 2 numbers
 
broke out the magnifying glass and it looks like FL C10u U442
 

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Cool. Anyone know what that translates into for a standard through hole cap? Thanks, Broodwich.

Robert
 
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