Min did the same thing. The switch went bad. The tech replaced the switch and now it works great. Mine was u der warranty so it was covered.My DSL40CR works with the 40W setting, but nothing from the 20W.
Since the 40 is ok, I would say the tubes are ok reading another post, still tried guitar straight in to fx return. Same 20w silent, 40w works. There is a slight "radio sparkle" but I would take that as interference from the surroundings. The 40W stage sounds just fine.
Any thoughts what I should try is much appreciated.
I know a little bit of soldering, so not afraid to fix. First "gig" ever in a week so timing of this was not ideal.