RX02 / DSD440 / SA801 problem

From: Tom Leffingwell <tom_at_sba.miami.edu>
Date: Fri Mar 8 20:10:49 2002

On Fri, 8 Mar 2002, Tony Duell wrote:

> What you are saying is that you have a good stepper motor connected to a
> good head positioner mechanism. You know it's good because the other
> logic board will operate it.

> You have a logic board that is outputting the right signals to the motor

Well, its outputing signals...I wouldn't go so far as to say they are

> And yet the motor doesn't run properly.

> Go back to the good drive. While the head is moving, look at the stepper
> drive singals at the pins of the ASIC (23, 24, 25 IIRC) and at the
> collectors of the ULN2074. In particular look at the mark-space ratio and
> freqeuncy.
> Now go to the faulty drive and look at the same signals. What (if any)
> differences do you see?

I'll check it out. What if the relationship isn't correct, like two of
the pulses are on top of each other? Is all the logic for generating the
pulses contained in the ASIC, or is it in turn driven by something
else? The ASIC from the bad system has no problem running the good drive,
so that's not a problem.
Received on Fri Mar 08 2002 - 20:10:49 GMT

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