Uniden PC78XL problem

I've had this radio for about four years now with no problems. The other day it quit transmitting and receiving. Stopped at a CB shop in Idaho and the tech said the finals were blown. He fixed it up and it worked for about twelve hours and quit again. It's a stock radio with an Astatic mic, no kicker. Twin Wilson 2000 antennas. What could be causing this? Thanks

 

Thanks for the reply Dave. The antenna light doesn't come on when transmitting. The coax makes sense as it's been shaking around in there for 11 years now. I haven't checked the SWR. I've got a down day tomorrow so I can tear into it.

Tom