Hum issue on a 2204 build.

[warioblast]

It's hard to tell, it was 5 years ago. I think I had a little hum / noise, even at low volume. I don't remember if I had hum with no guitar plugged in.
Back then, I didn't put much thought into heater, grounding, layout, wires proximity...

I asked a friend to borrow his scope.
 

[Willabe]

Have you read this before? It may help you.

http://www.valvewizard.co.uk/Grounding.html

Maybe you missed something or wired up a ground incorrectly? We have seen many times a bad filter cap ground connection or other bad ground cause hum. Maybe you wind loop?

I'm still very suspicious of those OT wires and what ever other wires those are that are running the length of the chassis directly laying on the heater wires and so close to the preamp tubes.  (I know you tried moving the OT/wires/jacks/z selector.)

Maybe you have a bad shorted shielded cable? If just 1 strand of the shield is touching the hot, that cause problems. Could be you melted the hot wires isolation but you can't see it, has happened here before.

I don't recall ever seeing that before in an amp that had no problems with noise.

[dwinstonwood]

First, my soldering leaves a lot to be desired, so I'm not being mean. But, do clean up stray solder blobs in your chassis. They can cause shorts and/or unintentional groundings.

[warioblast]

:) no worries.

It has been cleaned up already. I was worried about a potential short near one of the tube sockets.