Bally Solved The Addams Family (Bally, 1992) Speaker smoking

[Keldrin]

Picked up a Adams Family Pinball machine from the Texas Pinball Festival auction last weekend. Played it at the festival and it looked and played great.
So, got it home, and set it up, and it wouldn't turn on. Well, found that the fuse for the main power supply was blown. So, replaced it, and turned it on, and it blew without anything powering up.
So, looked at all the other fuses. They where fine. Tightened the screws on the board in the back box, and made sure all the connections where seated well. Then took the power cord plug apart and made sure that all the wires where in place correctly and none of the wires where touching.
Finally, replaced the power supply fuse again, and powered her back up. The machine booted but the speakers where buzzing loudly, then the mid range speaker on the left side of the back box made a loud pop noise, and started smoking. So, turned the machine off and unplugged it. Then watched the speaker continue smoking for another 5 minutes.
The wires connected to the speaker are soldered on, and the wires are not touching. There appears to be no break in the wire insulation as far as I can see. So not seeing where it might be shorting.
So, the question for me, is the speaker itself the problem? Or is the speaker the victim of some kind of short somewhere else in the machine?
Is this something I should be trying to track down myself? Or is it time to call a professional in to look at it? I've used the PinSmith in the past, on a Party Zone machine. And he does house call repairs.

 

[sleepy]

Sounds like the amp is overloading. Could be a capacitor or voltage regulator that supplies power to the amp. If the power is not being rectified (meaning smoothed to a steady flat DC voltage), then the AC variations will pass to the speaker.

And I'd be wondering why it would work when you bought it and not be working when you got it home. Can you tell if it is the same unit that you tested and bought? Did you check the ground pin on the wall socket?
You might hear a buzz if the ground pin in the AC wall outlet is not connected, and that can be very destructive, blowing fuses and the boards.

 

[Keldrin]

Sounds like the amp is overloading. Could be a capacitor or voltage regulator that supplies power to the amp. If the power is not being rectified (meaning smoothed to a steady flat DC voltage), then the AC variations will pass to the speaker.

And I'd be wondering why it would work when you bought it and not be working when you got it home. Can you tell if it is the same unit that you tested and bought? Did you check the ground pin on the wall socket?
You might hear a buzz if the ground pin in the AC wall outlet is not connected, and that can be very destructive, blowing fuses and the boards.

Yes, it's the same unit. Played before the auction and after. The weird part was, my last pass through the game room, the entire bank of games where it was plugged in was turned off. About 30 games turned off. Next day when picked up, it was already shrink wrapped and ready to load. SO didn't get to see it working again after the games was off.
The grounding pin is connected. Took the plug off as one of the first things to look at, since it might have gotten pulled on at some point durring the move. It all looked good. With the speakers disconnected, the game plays fine. Now, if I reconnect the speakers, there's no sound at all. No buzzing, no smoke, basically the same as if not connected. Not sure if that means I've damaged the sound board, or if the speaker going out, is the reason I'm not hearing anything. If the sound board went out, it did so without blowing either fuse, which seams odd.

 

[spalmer]

If the sound board went out, it did so without blowing either fuse, which seams odd.

Odd but not impossible. When you got it home and replaced the fuse, did you use the correct value. It almost sounds to me like the fuse blew when you got it home and then the fuse was replaced with an overrated fuse or the initial short that started the whole mess burnt something out. This may also help.

"Popping" Sound, Hot LM1875, and Speakers Shorting. Problem: pre-DCS sound board works, but eventually shorts the speakers. First the speakers start to "pop" (not very loud), every second or so. Eventually the speakers short and are ruined. Also the sound board's LM1875 heat sink gets very hot. DC voltage was measured at the speakers, and found to be 40mV (there should be no DC voltage). Solution: At first the LM1875 was thought to be bad. But the real problem was the capacitors feeding the LM1875. Caps C46-C47 (1 mfd Tant), C20 (10 mfd), C22 (22 mfd), C23 (.22 mfd) were replaced, and the problem was solved. Also the LM1875's heat sink now ran cool. The giveaway here was the DC voltage at the speakers, pointing to the capacitors. There should be zero DC volts at the speakers. As little as 5mV DC at the speakers can cause the LM1875's heat sink to run hot.

 

[Keldrin]

Well, when the PinSmith checked it out, he said there was something wrong on the sound board causing it to send out to high of a voltage to the speakers. It took out all of the speakers. Anyways, he replaced a part on the board. Then said, that the machine had original factory speakers, that really should be upgraded. So, went to Pinball life, and order some flipper fidelity speakers. Now the machine sounds better than ever!
(plus the PinSmith fixed some problems with my Party Zone while he was there, so was good for him to be there)

Odd but not impossible. When you got it home and replaced the fuse, did you use the correct value. It almost sounds to me like the fuse blew when you got it home and then the fuse was replaced with an overrated fuse or the initial short that started the whole mess burnt something out. This may also help.

"Popping" Sound, Hot LM1875, and Speakers Shorting. Problem: pre-DCS sound board works, but eventually shorts the speakers. First the speakers start to "pop" (not very loud), every second or so. Eventually the speakers short and are ruined. Also the sound board's LM1875 heat sink gets very hot. DC voltage was measured at the speakers, and found to be 40mV (there should be no DC voltage). Solution: At first the LM1875 was thought to be bad. But the real problem was the capacitors feeding the LM1875. Caps C46-C47 (1 mfd Tant), C20 (10 mfd), C22 (22 mfd), C23 (.22 mfd) were replaced, and the problem was solved. Also the LM1875's heat sink now ran cool. The giveaway here was the DC voltage at the speakers, pointing to the capacitors. There should be zero DC volts at the speakers. As little as 5mV DC at the speakers can cause the LM1875's heat sink to run hot.

 

[Isaac Sauvage]

what did the part turn out to be, if'n i may ask?

 

[Keldrin]

what did the part turn out to be, if'n i may ask?

I actually don't know. Sorry, he just told me he replace something on the board.