AC30 Build Making Static Noise

[Mike_J]

I have an AC30 build that sounds good for about 20 seconds after warming up.  Then an annoying static noise rides on top of the signal which sounds similar to the noise you get on an am radio station when driving under power lines.


Have looked over the amp using the yellow highlighter technique and don't see anything wrong.  Any help would be greatly appreciated because I am stumped.


Thanks
Mike

[Leevi]

First try to localize the root cause.

- preamp/power amp
- tubes, remove/change them one by one


One possible reason is the wiring inside the chassis,
open the wire bundles and try to separate the wires from each other and follow how it affects


/Leevi