Tv is on stand by but won't 'fire up'

Have a Panasonic tx-28dk2. Whilst watching it flicked off into stand by mode. Used the remote and it came back on 2 days later it did the same but would not come back on, the screen flicked as if to come on but immediatly turned back into 'stand by'. I systematically pulled out leads and came to unplug one of the 'push-in' speaker connectors (the 'sub woofer') and after I could turn it back on. It seemed fine. I reconnected the speaker lead thinking it may have been a coincidence as I had turned the power completely off during the taking-out-of-leads. All was back to normal. It happened again, going to stand by, so I went straight to the subwoofer lead, started up after taking the lead out. So I left the lead out. Wouldn't turn on again the next morning but the speaker lead was unplugged. Have unplugged everything and turned it on and off no joy, picture flashes as if to turn on for a fraction of a second then goes straight to standby and blank. I'm guessing its a power surge/short somewhere and the circuits are 'protecting' themselves. Any pointers for a quick fix? Or is it for the knackers yard? I DO want a new flatscreen but, I do like the picture and sound of this telly, and I could do with saving the pennies.