LA4 Noise

[Siegfried Meier]

Hey guys,

One of my LA4 blackface units is exhibiting some odd noise.  None of the controls seem to be at fault, so I'm thinking that maybe it's a transistor or something?

https://soundcloud.com/siegfried-meier-1/la4-blackface-noise

Any thoughts?  Much appreciated!
Thanks,
Sig

 

[radardoug]

My car makes a bumping noise when it goes round a corner. What do you think it could be?

 

[Siegfried Meier]

Wheel bearing bud.

 

[gyraf]

A pedestrian?

 

[gyraf]

On topic, there is little in audio path in there. My guess would be a tired electrolytic..

Jakob E.

 

[Siegfried Meier]

Hahaha.

Thanks Jakob!  I think a recap is in order for both these channels anyway, so maybe I'll just start there.

Sig

 

[Whoops]

When I had that sort of noise in the past was due to a transistor failing or from moisture.

I would replace the transistors and all the electrolytic caps.
And clean the board and contacts.

After that if the noise persists I would replace the IC's