RANDALL V2 400 W Hybrid Head

[CR Stokes]

Hello,

I am losing loss of volume and quality with my head. The volume comes and goes and there is a very annoying humming noise.

I've isolated the humming to the Main Volume control. The other three channels and their volume control have no effect on the level of humming.

Thanks.

I've uploaded the schematic.

[CR Stokes]

http://music-electronics-forum.com/t23160/

Here is the thread that lead me to this site.

[The Dude]

A loss of volume and a humming noise.
My first suspect would be loss of filtering on a power supply. Check ripple on supplies. Check that there are no filter caps that have come unsoldered or cracked loose from the circuit board.