hifi engine

Sound shuts off Receiver in 5 min of play?

I own a Technics AV Receiver, model no. SA-GX670 and after 5 minutes of play time the sounds shuts down. The impedence is correct, the ohms are correct; Iv'e tried reseting the receiver; the cooling fan kicks on; and there is no error message when I go to access the "Help" section. The receiver doesn't shut-down, just the sound. Let it cool down for about fifteen minutes and I'll get another 5 minutes of play time. Any suggestions?

Thank you,
Brad R.