Einstein FX Loop Hum

[Pearly Gates]

Having a bit of trouble with fx loop in my Einstein. Mostly on mode 3 and channel 2 there seems to be a lot of hum when I have cables plugged into either FX loop. It is worse in the parallel loop than serial loop. I have tried single pedals, same fx chain into different amps etc. the problem just occurs when the gain is higher on mode 3 ch1 and channel 2. Any idea what is going on or if there is something wrong?

 

[Pearly Gates]

Bumping this topic. My Einstein blew a tube and had to be repaired (all fixed now).

Tech still has the amp and he's had a look at it and the noise doesn't seem to be any problem with the amp i.e. a tube or anything.

Anyone know exactly what can cause the noise or how to fix? Even if there is just a cable plugged into the loop the noise seems to start straight away.