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.
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
