Ethan Dicks ethan.dicks at
Fri Dec 25 20:06:02 CST 2009

On 12/25/09, Roger Holmes <roger.holmes at> wrote:
>> From: Ethan Dicks <ethan.dicks at>
>> Oddly enough, one of my side projects is tracking down a problem with
>> the original controls for a Bridgeport Series 2.  One of the control
>> cabinets got packed with sawdust from an adjacent woodshop, so it
>> appears to be power-supply related (all the motor driver and pre-amp
>> boards check out, but only X moves; Y and Z make noise but are
>> stationary).
> If I remember right the series 2 used stepper motors.


> One set of coils faulty? But on Y and Z seems strange.


> Maybe there's something in common for
> the coils of both axes.

That is where I'm looking, but I'm new to the documentation, so I
haven't found it yet.  I expect it to be there - it's an
experience/familiarity problem, not a documentation problem.

> Rather less likely but the (woodruff?) drive keys
> could have sheared, but again on both axes at once seems unlikely. Do the
> motors turn or just go a tiny bit backward and forwards?

They do not move, but the motors do give a large amount of resistance
to manual turning (i.e., couldn't budge them by hand).

> Of course its possible one of the axes could have failed earlier and the
> machine used for simpler jobs.

I don't think that's the case but I can't report that from personal experience.

What I was told was that it worked perfectly until the
sawdust/overheating incident.  It's clear that neither Y nor Z move a
micron now, and that's under direct manual control from the panel.

One of the things we did do was to swap the X cable onto the Y stage.
It moved perfectly.  The Y cable wouldn't reach the X motor or we
would have tried that.

I am certain the Y motor is fine and the Y stage mechanics are fine,
too.  It's something further upstream than the stepper boards and the
pre-amps since those have also been investigated and the problem does
not move to the X axis under any board arrangement, and the Y and Z
stage never work, no matter how the boards are arranged.


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