Re: Stepper sings, but wont walk....

Hi,

Try running the motor at a very low speed, just a couple of steps a
second. If the motor takes 3 steps forward and a big step back, you
have a blown phase transistor. You can identify it it with an
ohmmeter. Measure the rasistance collector to emitter. A bad one will
show up as a near-dead short. Replace it and it may fly.

Mariss

--- In CAD_CAM_EDM_DRO@y..., "audiomaker2000" <audiomaker@s...> wrote:
> Hey all,
> I have been trying to repair a Bridgeport Boss that has a stepper
> which when told to move via the stock control "sings" and will sort
> of vibrate but wont actually turn. I've replaced every card in the
> machine with those which I pulled from my retrofit machine (and
> which are known to work), and the result is the same. I checked
the
> motor itself by switching it to a different axis circuit and the
> stepper works fine.
> So, I'm wondering what else besides the cards (drives, and stock
> CNC) that could cause such a condition? I'll probably just
retrofit
> this one too, but it is making me quite curious. All that seems to
> be left is cap's and wires.
>
> Thanks
>
> Sean