No bass on clean channel

I have a Fender "red knob" The Twin, today I noticed the bass on the clean channel has virtually died. What would cause this and is it a fix I could do myself - seeing as how I am 1800km away from the Fender amp tech. I was hoping it would be like a tone control on a guitar.
Clive

Sounds to me like either one of the three pot, resistor, cap, has gone out and needs to replace.

yup, sounds like a loose cap or resistor, ten minutes with a soldering iron and a magnifier will do it.

So if I take out the bass tone control pot and resistor replace it that should be it. By cap do you mean the capacitor that holds enough power to kill? or the little square bit soldered to the control pot?
Clive