Cyrus amp - intermittent problem?

[toast boy]

Hi all, I have a Cyrus III amplifier that occasionally doesn't output any sound. It's never dropped the sound whilst playing (that I've noticed) but I rarely turn it off and sometimes after it's not been playing for a while no sound will output from any input. The input switches appear to work with the LEDs changing but nothing from the speakers. Turning it off and on again at the main switch at the back of the amp fixes it (again, so far).

Anyone got any ideas what might be causing this? It's more of a minor irritation than a serious problem but if it's something that can be fixed I'd like to!

Cheers