After 1-1/2 years, my 1001 bit the dust at a gig with no warning. The shop guys say the power supply board went and they've ordered a new one. Still under warranty, thank goodness.
Might have taken a knockout punch from a transient on the AC line. Or maybe one room's line voltage was way off spec. Some clubs are notorious for bad power. So are some generators.
Sometimes a piece of gear can take a fatal hit but not exhibit the symptoms of it for weeks or months, then suddenly the problem will surface with no apparent cause.
Well, had the power board replaced under warranty, used the amp for about a month, and last night, *poof*, same thing again! Brought the amp in last night, no word yet.
I would check in with GK at this point and go over what is happening. There may be some other issue trigerring this and while your tech may have fixed the symptom, may not have cured the disease.
I've had that happen...and ironically, my problem was the same as yours. I blew it up...took it in and they fixed it...another month and it blew up again...they fixed it...I sold it.
If I were to buy another GK it'd be the 800RB or 400RB...those things are tanks. The 1001RB-II is like a frail old grandma. Love the sound but as a gigging musician, I can't have that kind of failure rate.