In article 01c37eb7$51ce5ee0$b797c3d8@race, Bob Paulin wrote:
DoN:

Any chance you know exactly what the electrical output is at the "jones
Plug" that goes into the magnetic chuck?

Volts, Amps, AC/DC?

With the rectifier bridge, it appears to be DC, but my limited
electrical/electronics knowledge keeps me from figuring out the
voltage/amperage.

I don't know the amperage, other than that it is limited by the
series resistor. But the voltage is 170 VDC with 120 VAC input.
Multiply the AC line voltage (nominal tops of 120VAC) by the ratio from
RMS voltage to peak voltage (1.414) to get the maximum voltage on the
filter capacitor, and thus on the mag chuck's coils. It won't *need* a
transformer.

The 35 Ohms resistor limits the maximum current to 4.857 A. But
if it were drawing that much, you would need an 8257 Watt resistor to
keep it from burning up, and you don't. I think that the current is
well below 1 A, but would have to measure the resistance of the mag
chuck. Even 1 A is a bit too much for the rating of the resistor found
in the machine, which looks like a 25 Watt resistor.

I was considering maybe trying to operate the chuck on a separate
transformer/converter.

What purpose for the transformer (other than reducing the shock
hazard a bit)? Normally, a transformer is used to change the voltage,
and here you're using the full voltage available from the AC power line.

The design shown will cost less than anything requiring a
transformer -- though you could drop the cost a little by replacing the
bridge rectifier with a single rectifier diode -- at the cost of a
little less strength of field at the magnet.

Ideally, you should perform the safety modification suggested in
the manual (if it has not already been done). The Jones connector on
the chuck should be male, with a female connector on the cable which
connects to that. This avoids having high voltage sitting on bare pins
with the plug disconnected from the chuck, but still connected to the
base unit. (It was included in a safety bulletin installed in the
manual.) They also warn about not using flood coolant with the
electro-magnetic chuck. Instead, you want a permanent magnet chuck, if
you have to use coolant -- and you want to seal off the connector port
in the housing.

Good Luck,
DoN.
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