JohnF wrote:

I have a 40hp DC motor in a machine set up for spinning. The motor
control (probably built by one of the Apostles) has done something bad
and I need to fix it. The system is Reliance and I'm guessing the
control is the original in this OLD Given lathe. I haven't used
programmable RPM control in the thing for years, I adjust the pot on
the spindle control box itself, so I need to figure out some way to
make it work.

Ideas.


I'm not familiar with what a motor control on a lathe is expected to do,
but I do know motors and controls. I also know you haven't told us
much. So:

What is it doing/not doing?
What is it supposed to do?
What have you done so far?
What did you find out?
What makes you think it's the controller and not the motor?

What is programmable RPM control supposed to do? Is that what's broken?
The pot on the spindle control box? Is that what's broken?

If the motor pulls loads of current but doesn't turn then you may not be
getting enough (or any) field current (per the other poster's response).
If there's voltage at the field terminals and no field current then
the field windings are broken. If there's no voltage at the field
terminals then the controller or connecting wires are broken.

If the motor doesn't pull current and doesn't turn then either it isn't
getting any voltage or something internally is broken - brushes,
armature wires, commutator, etc.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com