30 Apr
2024
30 Apr
'24
10:05 a.m.
On 4/30/24 10:46, Dominique Carlier via cctalk wrote:
Hello everyone
I need your help to identify an issue on my Diablo Model
40 Series. I don't know where to look, it's so vast !
Here's the problem:
When RUN is activated, the drive begins its spin up and
simultaneously deploys the heads (normal) but instead of
stabilizing them, the Head Positioner receives a burst of
reverse/forward micro signals. The heads "vibrate", this
creates an audible frequency "BRRRRRRRRRRRRRRRRRR", and it
is infinite, the heads are never loaded and the drive
never reaches READY.
At first I thought that perhaps the track zero sensor was
defective or something of the same order but when I
disengage RUN mode, the drive unloads the heads and they
should be in a fixed position, here they continue to
reverse/forward but more slowly than in RUN mode.
Because the heads continues to mess around even in unload
mode, this a priori excludes alignment problems.
Well, I don't know this particular drive, but I can think of
a few things to check. Presumably, this drive has some sort
of velocity sensor, either part of the voice coil assembly
or the head motion motor. It is possible that the velocity
sensor has gone bad, or that a wire to the sensor has broken.
Another possibility is that the track position encoder has
gone bad. They often are quadrature optical encoders, and
possibly a light bulb has failed or a photodiode has gone
bad or has a broken wire or bad sensor conditioning circuit.
If you have drawings for this drive, it should be easy to
follow this circuit. If not, then you will have to find
drawings and tech info. Hopefully, bitsavers has what you need.
Jon