STEREO SHUTOFF

It happens to just about everyone. One minute you’re listening to the hi-fi, the next you’re called away to answer the doorbell or a phone call. You forget all about the music, the record plays through, the automatic turntable shuts off — but the amplifier stays on until you happen to pass by and notice the glow from the pilot lamps. Yet, this simple circuit, which you can throw together in less than an hour, will automatically turn off the amplifier when the turntable shuts off. The relay coil voltage is taken from across the phonomotor; when the turntable motor is on, relay K1 closes and applies power to AC socket SO1; When the turntable shuts off, removing voltage from the motor, K1 opens, disconnecting power from outlet. Because the turntable automatic shutoff switch might not be able to carry the amplifier load, the AC power for SO1 is taken off before the automatic shutoff switch. Switch S1 bypasses the relay contacts and applies power to the socket even when the turntable is off.

Parts List For Stereo Shutoff

K1 – 117V AC relay with contacts rated at least 5 amperes at 117V AC (Radio Shack 275-207)

S1 – Switch, SPST (Shutoff bypass)

SO1 – AC Socket