Turntable speed

Is there a simple circuit and small that can be used to slow down a belt driven turntable that uses an ac motor controlled by line voltage? Perhaps a triac based circuit?

Thanks,
Paul

If you change the line frequency, the speed will change correspondingly. That requires a relatively sophisticated circuit that uses a variable-frequency power oscillator. Using a triac alone to chop portions out of the AC wave will cause the unit to run at the same speed, but with reduced torque.

I have sometimes reduced speed on a turntable like yours by remachining the motor pulley to make it smaller. This has been useful when the set originally had a 50Hz pulley that needed to be reduced to 5/6 the original diameter to run on 60Hz.

Fred Longworth

Hi Fred,

I have written you about this turntable before. I tried replacing the rubber mounting grommets for the motor as you suggested and it still runs fast. I temporarily wrapped the portion of the platter that the belt contacts with electrical tape to make it larger in radius. It is a unit that was purchased new in the US. It only developed this problem after being in storage for a few years. Would it be worth while to invest in a new motor or do you think that would not resolve the problem?

I'm really not comfortable trying to reduce the size of the motor capstan.

Thanks, Paul