Atari Basketball audio buzz/hum

pintom

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Just picked up an Atari Basketball project (big thanks to Creepykenny), game is working other than needing a cap kit and trackball rebuild but I have a loud buzz/hum coming from the speakers I replaced the caps on the audio amp board to no affect planning on replacing the big blue cap but I was told it was replaced five or so years ago any other ideas on what to look for?
 
Try gently flexing every connector you can get your hands on (or just those that carry power to the PCB and audio signals to the speaker...). My Asteroids was once humming, and it turned out to be poor connection at the PCB edge connector. Also fiddle with the wires at the speaker, and the connector lugs on the speaker, and the wires that go from the lugs to the coil. I had another game with buzz that turned out to be a bad connection (braided wire falling apart) between the lug and the speaker coil.

Failing that, there's always the audio amp itself.
 
This is where an oscilloscope comes in handy. You can quickly rule out the logic section and track down where it's coming from.
 
Changing out big blue didn't fix it next I'll clean up all the grounds and go through the connectors if that doesn't fix it I guess I'll be shipping the board off. LyonsArcade did your game sounds work along with the buzz?
 
Cleaned up the grounds and checked/cleaned the solder joints on the amp board connector still no luck. Can I hook up the audio outs from the main board to a set of amplified computer speakers to either eliminate or identify the main board as the problem?
 
check for loose fuse on the fuse holder.....i just fixed several Ataris and even Midways that had a loose holder for the fuse causing the hum!
 
I used a set of pc speakers and the buzz is coming from the board I checked the fuse holders on the ps they look fine and I tried it with the monitor disconnected just to rule that out before I ship this board off is there anything else on the ps other than big blue that could cause this?
 
I used a set of pc speakers and the buzz is coming from the board I checked the fuse holders on the ps they look fine and I tried it with the monitor disconnected just to rule that out before I ship this board off is there anything else on the ps other than big blue that could cause this?

really sounds like an AC buzz which would be a ps problem i believe! just checking the fuse holders phyically won't work. i ususally, while running, get something plastic and touch them each seperately to see if the buzz changes! if so, that's your culprit! if not, just might be a pcb issue.
 
Ok I replaced the 3 caps on the main board and still the freaking buzz at some point the connector on the ps was hacked to bypass the interlock switches could this cause a problem? How about the line filter any chance it could be the issue? Any other ideas please let me know I am really starting to despise this dam buzz!
 
dude, wiggle your wires to the fuses at the bottom of the cab...i bet it changes! it's gotta be an AC hum, and bad connection!!!

i don't think a big blue would cause this problem but not 100%. usually, if im not mistaken, a BB going bad just fluctuates the voltages making the pcb crash and what not!
 
I have poked, prodded and wiggled the entire power supply and replaced the only fuse holder that looked at all suspect I'm going to replace the TD2002A and the volume pot on the amp board just waiting on them to come in.
 
I'm at my wits end on this thing replaced the TD2002A and the volume pot on the amp board with no change it's disheartening to keep getting this buzz over and over no matter what I try.
 
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