ampeg svt2pro

[JC@]

This amp has new tubes, all of them.
But the sound fades almost out sometimes and them comes back to normal, for the first 15 minutes or so, until it gets stable I guess.

Anyone experienced a similar problem on one of these SVTs?

[Enzo]

Can happen to any amp. Did it do it with the old tubes?

New tubes is not a guarantee of good tubes - never forget that.

Isolate the problem, when teh sound fades from the output, does it also fade from the effects send, the preamp out , the anyplace else out?

[JC@]

Yes it did it with the old tubes I was told, it came in for a tube replacement and it is coming in again tomorrow to see if I can solve this issue. Apparently it does this for the first 15 minutes or so, after that it doesn't.
I will try to isolate the problem following your guideline.

[Enzo]

Just a hunch, if there is a 12AU7 in the power amp to drive the outputs, try replacing it.

[JC@]

Just a hunch, if there is a 12AU7 in the power amp to drive the outputs, try replacing it.
I will check that, but I believe I replaced those tubes also. The owner said it did this even before the tube replacement.
It must be very early in the morning in the USA... I say this because your green 'pilot' is lit-up!

[Enzo]

Pilot?

Also make sure no one swapped 12AX7 and 12Au7 positions.

[JC@]

Pilot?
Ups sorry. I meant to say the little green pilot light that appears like lit-up when an user is online.

[Enzo]

Yes 5AM here when you posted. Prime time for me, I usually close the shop and go home about 6:30AM