BurgerTime - buzzing from speaker

dkblue

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Hi,

I recently picked up a BurgerTime that had a power supply problem. I was able to switch with one I had left over from a Super PacMan. That's not really relevant to my problem, but I wanted to give all the background I have on it.

Now, as soon as I turn the machine on, there's a loud buzz coming from the speaker. I can hear the game sounds and music underneath. I ran through the sound tests and everything seems ok.

I unplugged the monitor and the light to rule out interference from those. I also checked and all ground wires seem to be secure.

I checked the voltages to the sound board, thinking maybe there were too many volts going to it, but the +-5v and 12v are all within a volt (5. something and 12. something).

Here's a video with the buzzing. You can hear the game sounds underneath.
http://www.youtube.com/watch?v=GvUXwnt1UOI

Anyone seen anything like this before or have anything else to try?
 
Last edited:
bad caps on the power supply

Thanks, I'll check them out.

I have a couple more questions that maybe you can help with. The original power supply was only showing about -2v but everything else seemed to check out. I tried messing with the pot (100 I think) but that seemed to do little if nothing. Is the -2v when it should be showing -5v an indication of anything? Bad caps maybe? Diodes? Something else?

Also, I had one more power supply that I tried. But when I was checking it for -5v (which it was showing) I accidentally shorted it to another pin. I think that pin had 12v on it? Anyway, it's not showing anything on the -5v pin now. Any idea what I screwed up? This was a quick screwup and I just tossed the board to the side in disgust without checking as much as a fuse, so that could be my problem. But in case it might be something bigger, I thought I'd go ahead and ask.

Thanks for the help.
 
Dokert's probably right in some bad caps. They act as filters, and if they're in-op, they'll let interference enter your sound system, hence the buzz. Also, I've had ground issues with antennas letting in interferance. This makes me also agree in a faulty powersupply to allow this interference. Bet it's a 60Hz buzz too haha :)
 
Dokert's probably right in some bad caps. They act as filters, and if they're in-op, they'll let interference enter your sound system, hence the buzz. Also, I've had ground issues with antennas letting in interferance. This makes me also agree in a faulty powersupply to allow this interference. Bet it's a 60Hz buzz too haha :)

Thanks for all the help guys. The problem IS in the power supply. I just need to figure out what cap(s) is causing it or buy a rebuild kit.

I mentioned the power supply I shorted above. Well, I checked the fuses and they seemed to measure OK. But one was off a little, which was weird. So I popped the fuse out of the "noise" board and replaced the one in the board I shorted, checked it out and got my -5 volts. So I popped that board in and bazinga! The game works great without even the hint of a buzz.

I'll ultimately repair one of both of the other boards for a quick backup solution should something happen to this one. But for now I'm ecstatic to learn the problem was not in the sound pcb.

Thanks again!
 
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