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My 15 yr old 1.5 hp motor 3450 rpm delta died last week. I temporarily replaced it with a 30 yr old 1/2 hp sears 1750 rpm bandsaw motor.Before I throw the motor away , it looks like there are 2 capacitors sitting on top of the motor .Do any of you out there know how to test the capacitance in an elec motor ?? Thanks.

Is the motor humming or do you hear anything from it? if a start capacitor is dead it should still have a hum to it. if a capacitor is bad you can usually push start the motor by spinning it with your hand. But be care as you can sand of your finger tips if it kicks in. Heres a wiki below that shows the testing procedure but be very careful as capacitors store high voltage and can discharge and harm you..Mike

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Another day, another dollar.

thanks michael . tried all of the above, no humming, no spin starting.More than likely the motor is dead. My jet 12 in bandsaw had a motor problem.I spinned the lower wheel, got it kick started, then replaced the capacitor at graingers.

If your cap bows you usually smell the dielectric fluid burn but it is not uncommon that you may not. Find a motor shop , they can test it. Often Caps are a cheap repair. Last one I put on a 5 hp motor was under $20

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Good advice above. No hum means the motor isn't getting voltage or there is an open circuit inside, so no current is flowing. I'd look at the thermal protection switch (most motors have one), the wiring/connections on the terminal plate, or the main on/off switch feeding the motor. Sounds like the latter is not the issue, as another motor works in its place. If there's an open circuit inside the motor, it's quite possible the capacitors are still carrying a dangerous charge. Here's what I would do:
1. If the motor is currently connected to line voltage, disconnect it and wait a minute. With a decent multimeter and 1 hand in a pocket, check the voltage across the terminals of each capacitor. If not zero, they must be discharged; let us know if so. If the V does measure zero, with 1 hand in a pocket, short a screwdriver tip across the terminals to make sure there is no charge.
2. After the caps are discharged, check the resistance across the main input terminals to the motor. It should be < 10 ohms.
3. Check the resistance across the thermal protection switch. It should be ~zero.
4. Check the connections on the terminal plate. They should slide on/off with some force.

Here's a typical diagram for your motor ("capacitor start, capacitor run"):
http://www.simplecircuitdiagram.com/wp- ... -Motor.gif

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David Malicky

Thanks Will test it first .I suspected the capacitors, as have rerouted the on/off switch to a taiwanese foot controlled on/off switch, until all the circuits are tested it is hard to diagnose the problem . thanks for the schematic