Shielding transformer/inverter

Thread Starter

johntp

Joined Jul 13, 2016
5
I’m building a frequency-voltage converter transformer for my vintage Lenco turntable. I’ve done a proof of concept using an 120ac to 12v dc transformer hooked to a 12vdc to 230v 50hz inverter. It worked, but the inverter creates a modified sine wave and a pure sine will be better for the motor. I’ve assembled a new converter/transformer using an LED driver and a pure sine wave inverter which takes care of frequency-voltage conversion ver well. It also creates an horrible noise in the speakers. My test setups made no noise. Here’s the difference: for the new converter I took the electronics out of the aluminum case and mounted them with the driver in a plastic Hammond case. Is this a shielding problem?
 

crutschow

Joined Mar 14, 2008
25,440
Here’s the difference: for the new converter I took the electronics out of the aluminum case and mounted them with the driver in a plastic Hammond case. Is this a shielding problem?
If that's the only difference then yes, it appears to be a shielding problem.
Was the aluminum case too large?
 

dendad

Joined Feb 20, 2016
3,602
For a turntable motor, what was often used is an oscillator driving an audio amp instead of an inverter. Then you can easilly have a clean sine wave.
 

Thread Starter

johntp

Joined Jul 13, 2016
5
For a turntable motor, what was often used is an oscillator driving an audio amp instead of an inverter. Then you can easilly have a clean sine wave.
Definitely sounds more sophisticated than my cludge Is this available off the shelf, possibly a simple build?
 
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