Speaker Hiss on Pinbot

learpilot2

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Jul 12, 2009
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HILTON HEAD ISLAND, South Carolina
I am getting a loud speaker hiss/squeal from the speakers of my pinbot. The squeal varies in pitch with the cycling of playfield lights. The loudness of the hiss/squeal is directly porportional to the volume control. Greater up turn up the volume, the greater the hiss. I checked all the pcbs for screws and grounding. They were tight and grounded. Any ideas? Hiss is present in play mode and attract mode.
 
Not sure, but I took this from Marvin Pinball Repair,

"Speaker Hum.

Replace cap C8 on the power supply. This little cap filters the supply to the IC1 voltage regulator (47uF). Ripple on the 5V supply from this cap being bad can cause hum. You can use another 47mfd cap for C8, or go as high as 100mfd."

Maybe its Capacitor C8 on your power supply?
 
Always check the easy things first. I had this hum noise on my High Speed when I first got it, it was loud during attract mode as well. Someone on this site told me to make sure all screws to the board were there and tight. Turns out I was missing 5 screws in various places, pulled a screw out that was there and went to ACE hardware got what I needed, put screws in and the hum went away. Get this I called the place where I bought it from, and they said "oh it old and older machines do that" Bull**** went up on this website and found the culprit. Thank you KLOV, otherwise I would have just been thinking oh it's old!!! I bet your missing screws, CHECK'EM!
 
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