Unsteady Volume Output from 200s

[jdf112]

On two occassions during the last month my 200s head has had trouble maitaining a steady volume ouput.  it would play fine for a few minutes and then the volume would just fade out. After flipping the standby on and off again the sound would come back on only to go away again a few minutes later?  I was wondering if anyone would have any ideas as to what is causing this.  All the tubes have been replaced within the last threee months, so that is not the problem.  It has only had this problem on two separate days and worked perfectly fine the rest of the time.

[Soundmasterg]

It could be a bad cap that is intermittantly allowing DC past itself into a following stage, which causes that following stage's bias to be incorrect. The cap can be troubleshot, or it can be replaced. The hard part is finding just which cap could be causing the problem.

It could also be a very high frequency oscillation that is causing the amp to appear to shutdown when in reality it isn't. It is just expencing so much power trying to amplify inaudible frequencies that there is nothing left for the frequencies you and I can hear. This could be due to many things like bad grounds, wire location inside the amp, etc. It needs to be troubleshot to determine if this is the cause or not, and if so how to fix it.

It could also be a malfunctioning volume pot. Replace it with a new one and see if it still has the same problem. Also make sure the ground on the volume pot has a good connection without any corrosion.

Greg