What would be the reasons a tube amps volume drops down for a short duration during play? When I use my Digitech RP200 hooked up directly in line with my amp, it sounds okay as far as feedback and overall distorton/gain, but it will cut out after 10 mins or so of use, stay down, and eventually return to the original level.

Can you use floor processors via fx loop? I connected mine via fx loop and it had the level of the volume drop consistantly. Anyone run those Boss or Digitech floor units through the fx loop? Anyone connect directly line in? I'm kinda new to the tube world and I know things are different as far as fx processors and stompboxes and how to run em. Thanks!

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check your powertubes.

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+1

sounds like overheating to me... thats what my friend's fender twin reverb does... after about 30 minutes... volume goes all over the place.

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How exactly do I check/test the powertubes? Just make sure they are firmly seated? Is this a sign of them going out maybe? Thanks for the replies guys!

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Yeah,just open her up,take a close look and see if there is any obvious damage.Check they all still work.How old is the unit,and when were the tubes last replaced?Could be time for a new quad.

Amp is a vintage Peavey VTM 120. I bought it off e-bay. I was told by the original owner that this amp has had less than 15 actual hours logged on it and that it has all original tubes still in it.

How can you tell a tube needs to be replaced by observing it? Are there any signs of stress one can notice?

Thanks for the replies!

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