On 4/30/24 12:37, Dominique Carlier via cctalk wrote:
Thanks for your response Jon :!
The technical documentation is available on Bitsavers here:
http://www.bitsavers.org/pdf/diablo/disk/model_40/81603_Diablo4xMaint_Apr75.pdf
But also here:
https://www.wang2200.org/docs/external/DiabloSeries40DiskDriveFieldLevelMaintenanceGuide.03-0057.pdf
I thought like you about the sensors, but here the
reverse/forward movements even after unloading the heads
lead me to think that the issue is at the level of the
circuitry involved in the control of the head positionner
linear motor.
I would like to be able to follow the diagrams easily, but
it is incredibly complex.
The only good news is that it is perhaps easily
identifiable for those who specifically know the Diablo
model 40 series disc drives, in the video we can observe
very briefly that these reverse/forward movements start as
soon as I press RUN, even before the machine begins to
deploy the heads. Precisely here:
https://youtu.be/HzzxLnSdEOg?t=4
We could deduce that this is a problem at the very base of
what balances the voltages for controlling the linear
motor.But even in this case, my limited skills do not
allow me to direct my research, which is why I need some
advice ;)
On 30/04/2024 19:05, Jon Elson via cctalk wrote:
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.
OK, without looking at the docs, generally these types of
drives have a linear amplifier that takes a velocity command
from some control logic and a velocity feedback signal from
a sensor. When the run switch is turned on, the servo amp
might be enabled, and then the amp gets a zero velocity
command. When the disc is up to speed, the velocity command
is set so that the heads load onto the pack, and then track
counting logic moves the heads to the desired track. With
the heads advancing as SOON as the run switch is flipped on,
then it seems like the command to the amp is happening at
the wrong time. It seems pretty clear the velocity servo is
working properly, as the motion looks very smooth. But, the
heads move toward the pack, and then some kind of safety
circuit must be tripping as the pack is not up to speed yet.
This will take some careful debugging.
Jon
