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AC Feedback from DC 110v Power Supply

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grabasphalt

New Member
Greetings,
I'm having trouble with the power supply that powers my mini-lathe. It is a 110 volt Input, 110 volt output DC Power supply that employs two Mosfet 500v IFRP460 transistors. The problem started when I overheated the power supply by overworking the motor. Right before it quit, the brushes on the motor started throwing sparks indicating an AC voltage leak to the motor. When I pulled the unit apart, I found the Mosfets to be wiped out and the main power resistor was cooked as well. After replacing the transistors and installing an alternate resistor, the unit shows 110 volt DC and 55 volts AC going to the motor. The number on the original resistor was 10WR33j. The resistor I used is a regular sand resistor rated at 10 watts and .33 ohms. What does the j mean on the original resistor ? Does the resistor filter the AC current from the power supply ? The unit is variable and doesn't employ a wire wound transformer. I am a NASCAR mechanic, and my knowledge of electronics is limited. Please help !!! Sincerely, Dale Openshaw
 

Gene

New Member
It might be helpful if you coud post your circuit. Since you mentioned the MOSFETs, I would assume the power supply is variable - making the lathe motor speed adjustable. I would have expected a capacitor in the circuit and I would have expected it to burn out when the resistor went. A little more info would mean a lot.
 
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