RD112 in United Kingdom, needs repair

does anyone know a musicman amp specialist living in Britian. I have had MY RD112 One Hundred . It's been fixed several times but the fault keeps coming back i.e. volume dips and sound breaks up. If I turn the amp on and of several times it returns to normal. Only to do the same again after a few minutes. Please help i've tried other amps but nothing compares.
Richard

What repairs were done to it before? Did the repairs seem to work only to again fail later? How much later?
A few of us here might be able to take some educated guesses if we had all the specific repair information & history.
Steve