TV shuts Off; this time we can't turn it on again!!?

Hi, my tv was recently repaired, costing about $300 in all. The guy took the inside of the t.v. to his workshop for 4 months. The part he replaced is still under guarantee.

However, since we got it back it began to shut-off periodically and we had to keep putting it back on. The last time it shut-off, the "ON" light went out and we can't get power back to the television at all. Is this fixable? It seems to me like something, somewhere, has shorted or burned out perhaps? Maybe there is a "reset" button somewhere?

The repairman offered to take the t.v. away again and fix it, but I am concerned that he might say it wasn't the guaranteed part that went this time and charge me all over again! The T.V. is:-
"RCA Home Theatre" (super large 5?" screen);
"Twin Tuner Pip";
Model:P46733AT;
Service No P46733ATLX1;
manufactured September 1996.

Just supposing it costs me an additional $300 then I could have bought another one by then! This could go on for ever!

If anyone can offer advice, we would greatly appreciate it. Thanks.
fri10u@yahoo.com