My original 1972 Delco AM/FM stereo 8track cuts out on the left channel only after the radio warms up (about 10 minutes). After it cools down it will repeat. Right channel is OK. When I spray Freez-it on one of the Delco DS-515 output transistors, the left channel comes back on for about 1 minute, then cuts off. So I'm thinking one of my output transistors is bad (the big ones located in the heat sink). Anybody have experience changing the output transistors and drivers for this type radio? And where to locate these transistors? Or a good experience with a repair shop? Thanks for any help.