Played a short set a couple of week ago and my sound vanished just as we started our 5th and final song. I hastily traced my cables to make sure nothing had come unplugged, then turned off the amp and swapped the the speakon speaker cable for a regular TS jack to jack cable, turned back on and had sound for a couple of seconds before it died again. Ended up stopping the song and was able to plug into the desk so we could finish our set. after we finished I remembered reading about the thermal protection circuit and put it down to that, or maybe dodgy power in the venue. Tried it at home the next day for 2 or 3 hours - albeit at quite low volume - and it was fine. Fast forward to rehearsals this morning, the first time I had used the amp since. Worked fine for about an hour and cut out. Turned it off for about 10 or 20 seconds and tried again and got about another 20mins out of it before it cut out again. This was using a rented 4x12 cab as opposed to my usual markbass 1x12 traveller cab. So I can rule out the cab causing the problem, or leads as I had tried both the first time it cut out. When it cut out today I checked to see if the fan was working, which it was and it didn't feel warm to touch at all. So I'm thinking perhaps it's not the thermal protection kicking in - maybe a short of some kind. I should add that at that first gig, when we we unloading the car, my amp fell out onto the floor when we opened the boot - it's aways in it's markbass padded case and the fact it powered up made me assume it was ok. But as one of my band mates said to me, it may have worked something loose causing one of the protection circuits to kick in. I have opened it up tonight to see if I could find anything obviously loose, which I couldn't, I also looked for signs of dust and fluff, of which there was a small amount on the huge heatsink near the vents - not enough to cause overheating IMO. FWIW, although my bass and pedal board are quite high output, I always set the gain appropriately so that it doesn't clip, eq is close to neutral, and I don't use the FX loops (I read on a thread that these could cause a short). Any ideas of what to try before I take it for repair, or anyone else experience similar issues?