Subway rocket problem

[brian b]

Just picked up a very clean subway rocket, and just put new tubes in to fix a microphonic problem. Well it is still there on the dirty channel with nothing plugged in it starts to just squel and produce a high pitch sound it goes awat when you turn the treble alll the way off or if you turn the volumes down to 0 . Any suggestion.

 

[brian b]

Thanks for the input decided to sell