Hello, I have done some reading but wanted advice on getting rid of the background audio hum on my Firepower whenever it is powered on. I have owned the game for 25 years and it has always hummed somewhat, however it is noticeable and annoying now that I have hooked up to an external hi-fi audio system. Some advice has recommended replacing capacitors on the sound board, while others suggest removing extraneous ground wires on the sound board?

Also, can anyone confirm if the slingshot bumpers on Firepower are supposed to generate sound effects when activated? I recently switched out to Rottendog MPU/Driver combo board, and I feel like I used to have sounds with the sling shot bumpers but now there are none. All other sounds seem fine across the game.

#firepower

Good question, I just checked they are kicking but not scoring any points or making any sounds.

Ok thanks I will check that. Thanks again.

zacaj Thank you - you were 100% correct both sides the switches under the playfield were dirty and/or out of adjustment and not
contacting when the slingshot kicks. Easy to fix, thanks for pointing me in the right direction.

OK thank you, I will check all these things you have suggested.

I did do all of the things suggested by Schwaggs but did not isolate the source of the hum.

Except, I did not figure out which shield is indicated? Where should that shield be placed?
I did not see any shield indicated on parts list so would appreciate guidance.

Also, I should have mentioned another odd thing with the audio which this machine does upon power up, it makes a louder buzzy blurb sound for about one second then tapers off to a milder ongoing hum.

Can anyone confirm if their Firepower machine makes this continuous (60 Hz?) hum and/or makes the short buzzy blurb sound when powered up?

The hum is not a big deal normally but since I have hooked up the powered sub woofer it is quite annoying. As comparison, my Whirlwind machine makes no hum at all.

OK I figured out what the shield mentioned above refers to the braided wire shielding surrounding the volume control wire. So yes, the shield
is connected.

Thanks for your advice. I have rotated the volume and balance controls many times, inspected and re-seated all the grounds and tested continuity to grounds everywhere, have disconnected the volume control and also the solenoid connector for the sound board and the "hum" persists. It only goes away if I disconnect either the speaker or power connector on the sound board (obviously).

The machine buzzes/blurbs for a second upon power up, but what I am trying to solve is the continuous HUM ongoing after power up ... since I have now connected a good external speaker and powered sub woofer set up, the hum is very annoying through the sub woofer.

I ordered five capacitors today to replace C14 C15 C25 C26 C27 on the sound board, hopefully that may fix the humming issue.