Quote:
Originally Posted by wasyoungonce
I found that many FET (or transistor) PWM dew heaters switched the heater thru Vcc rail. Thus when the output driver device was off there is Vcc (in most cases +12V DC) sitting on the outer shell of the heater connector. Some/many of these commercial dew heater use a metal RCA connector & +12V sitting on this outer shell is recipe for trouble.
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Is there a way to test the PWM dew controller (using a multimeter) to see if this is a problem? Would you see a voltage between the earth on the input to the PWM and the outer shell on the outlet when the load is turned down to minimum?