Los Angeles, CA
Would the transformer cause this? Making my soundboard make crackling noises.
(Topic ID: 246385)
No, the sound board doesn't get its 12 volts from the transformer. The sound board takes 43 volts from the solenoid bus and turns it into 12 volts through components that are on the sound board.
2 weeks later
Quoted from DTAC:hmm, weird it sounds ok for about 10min then starts crackeling. this a new sound board. any ideas?
A common issue for noise is that the sound board is sensitive to ground problems. The 43v ground return is isolated back to the driver board J3 P23. The rest of the board ground return goes to driver board J3 P20 and also to the screw down mounting point to ground against the backbox plane. If any of those connectors get resistance it can make the sound board noisy.
A lot of times an easy work around is to back off the sound board from the mounting bracket so it does not ground against the backbox plane. Try that and see if the problem goes away. If it does there is probably a connector issue somewhere. Make sure the backbox ground braid is connected. Driver J3 connector is in good shape and the driver board ground screw down is in. Sound board connector is in good shape. Rectifier board 20p head connector is in good shape.
The 12V on this board is just a close approximation based on a 13V zener diode. 13.8 would be fine.
What does the +5V look like? Good connection back to his source?
For a new board - if 5V is good, I think I would ask the manufacturer on this one, a new board shouldn't be doing this.
Original board had the typical isolated ground for the filter capacitor ground. Nobody knows what possessed Bally to do this, hopefully the replacement board didn't do this. Make sure pin 15 ground pin is a good connection. Almost tempted to say that TP2 and TP3 should be tied together BUT I haven't taken the time to look at the actual connections to make sure there won't be an issue with this ...so don't do this now.
Bally had a thing for isolating the grounds which seems to cause more problems than it fixes. Some of the grounds are isolated on the driver board back the transformer rectifier board and then they isolate other grounds back to the driver board. I have seen noisy sound boards sound fine after you connect TP2 and TP5 together with a gator clip or pull the board up off of the backbox mounting plane and insulate the mounting points. It usually ends up being bad connector at driver j3, the sound board, or the rectifier board. Most of the time people just back the sound board off of the mounting brackets, then it sounds better and leave it that way.
Quoted from G-P-E:Original board had the typical isolated ground for the filter capacitor ground. Nobody knows what possessed Bally to do this, hopefully the replacement board didn't do this. Make sure pin 15 ground pin is a good connection. Almost tempted to say that TP2 and TP3 should be tied together BUT I haven't taken the time to look at the actual connections to make sure there won't be an issue with this ...so don't do this now.
The replacement still has the isolated grounds. I knew it was more likely to not be noisy from bad connectors with the grounds connected from testing, but I thought Bally may have had a good reason to isolate them that I did not understand. It worked for 40 years with grounds isolated so left it that way. That board is pretty much finalized, but maybe I will update it so the 43v ground is not isolated.
I did common up all the grounds on the driver board replacement.
1 month later
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