If the PS3 is on and was working fine before the TV went out to get fixed, and this TV is set to the appropriate output then I'd say it's this TV that either isn't working outright, or its AV input isn't working. The PS3 itself should automatically recognize that it's connected by an AV output and output the video over it. If you have a second output on that TV I'd try to hook it up to that and see if it works, or at least hook something else up to the TV to confirm it is the TV that's the problem. I have had TV inputs crap out on me before though so it does happen.