Tell me how it went "boom". If it went "boom" in a particular way (wide open triac fried the field coil), your technician is correct. Parts are unobtanium. Otherwise, most parts are available or suitable substitutes can be found. I think the best thing to do is to find out from your tech why he says it is unfixable (i.e., which part), and then call Roland.
It should sound like it isn't there!
There is a difference between hearing and listening...
Making life enjoyable through expensive electronics.
Carver: C-4000 & C-1 preamps, PSC-60 preamp/tuner, TX-11a tuner, M-400 (2), C-500, M-500, M-500t, M-500t Mk.II, A-500x, AL-III loudspeakers (2 pr.)
Sunfire:Theater Grand III processor, Ultimate Receiver, Cinema Grand Signature 400 ~ seven, True Subwoofer Mk. II, D-10 Subwoofer