Newer Porter-Cable VS Grinder Died - Need Some Motor Help

I have a Porter-Cable 8" variable speed grinder that worked for a total of only hours, including balancing and so forth. The unit is out of warranty. Investigation showed a blown fuse which I was finally able to acquire through Amazon. New fuse blew immediately, no surprise there. As far as I can tell with a VOM (no capacitance setting) meter the start cap appears good.

Below are pictures of the device. The AC power cord runs into the control circuit board where the fuse is. A set of three wires runs from the control circuit board to the variable speed control and another similar cord runs to the motor. This is the only wire(s) going to the motor except for the capacitor.

Taking it to a repair shop will cost more than the unit is worth. Any educated or otherwise obtained ideas?

Overall shot:

View attachment 88372

Wires enter and exit control circuit board:

View attachment 88373

Cable with three wires runs to VS control:

View attachment 88374

Cable with three wires runs into motor housing:

View attachment 88375

I'd be very happy if I could just get it to run without the variable speed. I would be very, very happy if I could get it to run at only a low speed.
 
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Guess = Something on the PC board took a nose dive???

I've had an electrical storm waste a coffee maker with a PC board--bricked it.

(My coffee tastes the same as it did in the old machine without the PC board--LOL)
 
http://www.sawmillcreek.org/showthread.php?202609-Porter-Cable-VS-grinder-problem - same problem - ended up being a blown board.

http://www.ereplacementparts.com/porter-cable-pcb575bg-bench-grinder-parts-c-129_1811_130232.html - (I think? that's your machine) claims the board is $46 - ouch!
http://servicenet.blackanddecker.com/Parts/Detail/284076 - $40 here (black and decker, but looks? like the same unit? maybe?).

Don't really know what kind of motor that has, might be able to just rig up some other sort of regulator to tune the speed down cheaper maybe.. (not sure if its voltage or frequency being changed here).
 
I know that it may be of no help, but unless the variable speed is critical for what you want, you could try bypassing the board and converting it in a fixed speed grinder, at least you would have a machine that would have a use.
 
I did some searching on this and didn't have much success. Variable speed motors are usually of the universal type and actually run on DC. But they have a wide speed range and low torque most often. This seems different as it seems to be a real ac single phase motor with limited speed control. Not even sure how these work as AC motors are usually speed controlled by governing the frequency of the AC drive voltage. Inverters and such and are almost always 3 phacse motors...

So much for what I thought I knew...
Garry
 
I know that it may be of no help, but unless the variable speed is critical for what you want, you could try bypassing the board and converting it in a fixed speed grinder, at least you would have a machine that would have a use.
Dad would love to do this but, with three wires going to the motor from the circuit board we are not sure of which does what. After we percolate on this for awhile we may just give it a shot and see if we can get the grinder to just run single speed. If we are able to do that as opposed to burn it up trying, he can definitely use the grinder.
 
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