Big problem in Fx Loop

[raza]

Hi !

I have finish a new amp but I ve a problem with the Fx loop.

The fx loop can be switch. When the fx loop is on, I have a noise and when I UP more than 12 oclock the power in level, The amps starts to CRY and make lot of noise (OSCILATION NOISE).!


What can I do? The tube si a Tung sol 12ax7.
How I can reduce the signal?

subir fotos a internet
Thanks!

[raza]

The power in level Pot is a 250ka pot, same value for VOL pot.

[danman]

Since you mentioned that it was a new amp, did you try to play it before installing the loop? The reason I ask is that it is common to have to swap the OT primary wires on new builds that exhibit this same problem. Usually swapping the wires going to pin 3 of the power tube sockets will fix the problem.

[raza]

Hi,

It'snt problem from the wires of the Ot becouse when I Switch off the Fx loop, I bypass ther return Stage, and it sounds very good.

Also I test to put the guitar for the return, And the amp sound good, only with the power in Level.


I dont know whats happen....

[danman]

Ok, just wanted to check that first. I don't have much experience with the loop so hopefully one of the fellas will have some suggestions.