8 Mar
2002
8 Mar
'02
12:10 p.m.
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.
Correct.
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
correct.
And yet the motor doesn't run properly.
Nope...
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.