Hard Drive problem fixed

[casa@unm.edu (Jim Pittman)]

If anyone cares, my Tulin Quantum hard drive problem seems to be
fixed. Last week I said:

> Having never seen the insides of a hard drive case, I opened it
> up. There were two wires, a red and a black, going from the power
> supply to the LED in the top part of the case, and a blue wire
> going from the power supply to somewhere underneath the front end
> (the end away from the two SCSI connectors) of the Quantum hard
> drive. So I couldn't move the top cover very far from the drive
> because of these three wires.
> 
> Well, in cleaning out the dust the blue wire came loose! I took out
> four screws holding the drive to the chassis so I could look to see
> where the wire had been connected. The only places I could see that
> could possibly accommodate the tiny female connector on the end of
> the blue wire were pins on two tiny connectors at the end of the
> Quantum motherboard. One connector had two pins, the other had five.
> There were no meaningful identifying markings on the connectors that
> I could see; it said something like "J5" and "J12" or whatever.
> 
> The red, black and blue wires come off the power supply board at
> the same place and the board says "LED" near where the wires are.

I hooked up the drive to an Apple HS SCSI card, leaving the blue wire
disconnected. The drive seemed to work fine. The LED was on whenever
the drive power was turned on, but didn't "flicker" when writing as
it used to do. I checked the small connector pins and found a low
voltage on the left-most pin of the left-most connector (the one with
two pins) when the drive was writing. I attached to blue wire to this
pin, and now the LED "flickered" when the drive was writing. I put
everything back together and pronounced the drive "fixed."

My theory is that drives that have two LEDs (one to be turned on when
there is power to the drive, one to turn on only when the drive is
writing) use the red and blue wires for these LEDs and the black is a
common or ground. The Tulin drive only has one LED and therefore uses
the intensity of the LED light (the "flickering") to indicate writing.

It is too bad neither Tulin nor Quantum provided documentation to show
where this blue wire was supposed to be attached, especially since it
was so easy to dislodge the wire.

Thanks to Randy for his helpful suggestion.

- Jim Pittman - AppleQuerque Computer Club - casa@unm.edu