amplifier wanted

Have 1980's vintage receiver,it takes 10-15 min. for any sound to come out of it.It also cuts out often and then will come back on.Could this be transformer or capacitor related?Thanks for your help,Bob
You didn't say if it was tube or SS, but I'll assume SS because of the vintage and the obviousness of a tube problem. Capacitor or resistor (heating/cooling makes for auto_intermittancy)is a good possibility or oxidized solder joint. You might check whether physical pressure or tapping on the board (assuming SS and cicuit board) has any affect. If so, this could bring bad solder joint to the top of the list.
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Good point about both channels, E. A common TV problem with same symptoms is old dried up electrolytic cap in power supply. Perhaps you have a meter and could monitor the power supply output voltage.