High frecuency noises with bias trimmer.

[chocopower]

Hi there,
I have a 90´s Orange Overdrive with high frecuency noises. In fact i can recognice two diferent noises.
One continious and the other is more like... "phone interferences".
The strange is that both disapear with bias pot at minimun...

Reverse diode is ok.
¿should i suspect from the bias filtering?

That amp have suffered some really serious problems.
The owner tell me that power transformer have been rebobined, and OT changed. After that it had been blowing fuses till another tech found some mistakes in the wiring...

As i said. ¿should i suspect from bias filtering?