[vcf-midatlantic] Mac SE coming to Workshop

Dave McGuire mcguire at neurotica.com
Fri Aug 11 17:04:21 EDT 2017

On 08/11/2017 04:56 PM, Jonathan Gevaryahu via vcf-midatlantic wrote:
> I've got two dead miniscribe HDDs from two Mac SEs, I think the optical
> gate sensor for the external track 0 sensor on the head stepper (these
> don't use a voice coil head!) goes bad, and I'm not sure how to fix it.
> Symptom is the drive ramming the head into the "track -1" head stop and
> making a loud racket.

  This should be a fairly easy diagnosis.  Check the opto-interruptor
out of circuit.  The LED is most likely IR, so its Vf should be 1.2V to
1.5V or so.  Check that, possibly using a camera with good IR
sensitivity (use a known-working remote control to check various phone
cameras, standalone digital cameras, etc) and see if you get emission
from the emitter side.

  The detector side is almost always an NPN phototransistor; check that
as such, wrap a small circuit around it (watch current!) and hit it with
a flashlight.


Dave McGuire, AK4HZ
New Kensington, PA

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