Hey Ben, just last week my trusty system encountered the same problem. I've had it for nearly 10 years now and was kinda hoping you managed to finally get yours fixed (therefore giving me some hope!). Anyways, I read that it may be a problem with the poweramp or perhaps a faulty speaker. I realise it was about 2 years ago you posted the problem up, however I was hoping you could tell me if you ever manage to confirm either of these, and did you ever get your system fixed. Any help or info would be very much appreciated.

I have a Technics DV170 4 x modular hi fi system and the tuner/amplifier has this "F61" power off problem after about 15 minutes of use. Extra cooling doesn't seem to help! I'm looking for help also. Rgds Ben