Re: Servo Dynamics 1525 servo drive noise

Jon...

I might havein my files, a complete schematic of 1525 board, if so
would you like a copy??...Richard.

>
>
> shawncd2001 wrote:
>
> >I recently purchased an older Milltronics Partner mill. This
> >particular unit uses the older Servo Dynamics 1525 servo drives.
> >I have tuned the drives to where they perform the way I want them,
> >but there is an ear piercing whine or whistling sonund coming from
> >the boards. Anybody out there have the same problem? Any ideas on a
> >fix? Any information would be much appreciated.
> >
> >
> >
> Yup, these older drives have very low frequency PWM cycles, and so
> produce lots of audible tone. Looking in the book, it says it is 16

KHz.

> Most people past their 20's can't hear much up there anymore. This

would

> be the same pitch as the horizontal output of a TV set.
>
> I'm wondering if what you are getting is a subharmonic or unrelated
> lower frequency than the 16 KHz? Can you make the pitch or loudness
> of the tone change by moving the axis to a different position, or
> manually damping the shafts (motor, encoder, tach) with your hands?
> Can you make a guess at the frequency of the tone? Are you sure it
> is coming from the servo amp, and not the motor?
>
> You might also disconnect or disable all but one amp at a time to see
> if it is one particular amp, or all of them emit this tone. If you can
> disconnect the velocity command signal from the CNC control to
> the amps, you can see if this is a positioning loop oscillation, or
> just in the servo amp.
>
> The Servo Dynamics does have inductors on the output. They appear
> to be quite small, so it doesn't seem likely they are emitting much
> sound. There is a large transformer (T3) on the circuit board. I have
> only partial schematics of this amp, but I assume this is a DC-DC
> converter that provides isolated power to floating circuits in the
> amp. It may be running at an abnormally low frequency. Without
> diagrams, I can't go much further. You could try wrapping foam
> around this transformer, but if it already runs hot, that might not
> be a good idea.
>
> Jon