Dead IMI-drive (was Re: Onyx C8000: good news and bad news as well)

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Wed Sep 15 18:47:55 2004

>
> > >The IMI 7020 hard drive is dead and cannot be fixed:
> > >The damn coil of the motor causes a short circuit :(
> >=20
> > I'm sure you checked, but possibly could it be motor braking electronic=
> s or=20
> > the good old reversed diode across the windings that have shorted, and =
> not=20
> > the motor coil itself?
>
> This reversed diode sits on a small PCB outside the motor. =20
> I disconnected it, having the two wires of the 24V DC Motor in my hands.

How many wires does this motoe have in total? If quite a few (6 or more),
then I would suspect a motor with electronic commutation on one of the
drive PCBs, and it's quite common for the windings of those motors to
have very low DC resistances (< 1 ohm).

If there are only 2 wires, presumably power connections, I would still
suspect an electronically commutated motor (you need to keep the speed
pretty constant after all). It's possible there's some circuitry inside
the motor, and perhaps a trnasistor has gone short-circuit or something.
Can you get inside the motor at all without opening the HDA? (I know it's
possible to remove the winding assembly from the motor on a Micropolis
1200 in the field, but it does need special tools...)

-tony
Received on Wed Sep 15 2004 - 18:47:55 BST