[ARC5] dynamotor resistance

[Mike Hanz]

On 12/11/2013 3:15 AM, Tom Elmore wrote:
> Does anyone know the proper resistance of the high voltage winding in the
> MD-7 modulator dynamotor? I am seeing about 130 ohms which seems low to me.
> I have the motor all apart and haven't spun it up fully yet.

I'm assuming you are referring to the HV shunt field winding?  That is 
somewhat lower than the "approximately 170 ohm" figure given in the 
manual, but not wildly so.  Slap 28 volts across the winding for a 
couple of hours and see how hot it gets.  The current should be on the 
order of 165mA or so.  If it gets more than reasonably hot to the touch 
you may have a shorted winding in the pack somewhere. I've never found a 
field coil that had an *internal* short in it, but it's always 
possible.  Usually the shorted windings are in the armature - probably 
due to the mechanical forces on it during operation.

73,
Mike  KC4TOS