Buzzing from speaker

[GodMcB]

Hi,

I just got my first pinball table which is Teenage Mutant Ninja Turtles. It was a gift from my uncle as he was clearing out his flat.
Everything is great except after about 10 to 15 minutes of play, there is a loud buzzing coming from the left speaker. The buzzing is unaffected by the volume control and remains if the machine is turned off and on again.
The only way to temporarily fix this is to switch off, leave for a few minutes and turn on again.

I tried looking online and seen suggestions about ensuring the boards are grounded. Everything seems ok but thought I'd post here to see if there are any other suggestions.

Thanks,
Gordon

 

[stoptap]

Welcome Gordon.

If it was down to the grounding it would do it all the time, not just when it gets warm.
Sounds like it could be an amplifier chip that is going out of spec when it warms up.

 

[stoptap]

A little bit of further info here.

http://techniek.flipperwinkel.nl/desega/index3.htm#sound

 

[GodMcB]

Thanks for the quick reply.
I thought that about the ground issue too, unless somethings moving if it moves with expansion as it heats up, but I think that's unlikely.
I'll look into the link you send and see what I can find about amplifier chips.

I'm all new to this so might take me some time but I'll report back if I find an answer.

 

[stoptap]

I have diagnosed a dodgy amplifier before with freeze spray. When it got hot and started acting peculiar I sprayed it with the freeze spray to cool it down. It immediately started working correctly until it got hot again. I then knew exactly which part to replace.

 

[GodMcB]

I don't have a freeze spray but I tried blowing cold air over the sound board with a cold hairdryer and the buzzing stopped straight away.
I'll get some freeze spray so I can narrow it down to the part.
Thanks for the suggestion and your help so far.