Teac FD-55B Floppy Oddity

From: John Chris Wren <jcwren_at_jcwren.com>
Date: Tue Feb 26 22:55:39 2002

        Thanks! Perhaps this will be a start towards debugging it. I do know that
the head load solenoid is on a 2x3 connector, and uses the two end pins.
Three of the remaining 4 pins go to the home position opto sensor, and the 4
is an index pin. But I suspect the overall drive topology is pretty
similiar, and probably uses a +12 load/+5 hold also. I'll check that out.

        --John

> -----Original Message-----
> From: owner-classiccmp_at_classiccmp.org
> [mailto:owner-classiccmp_at_classiccmp.org]On Behalf Of Tony Duell
> Sent: Tuesday, February 26, 2002 23:16 PM
> To: classiccmp_at_classiccmp.org
> Subject: Re: Teac FD-55B Floppy Oddity
>
>
> >
> >
> > My Otronas have FD-55B-01-U drives in them. I thought the
> drives were
> > fried, since they wouldn't work on the Otrona nor on the PC,
> but in dinking
> > around, I determined that on at least one drive (and probably
> the other),
> > the head load solenoid is not pulling in. I see power being
> applied, but it
> > only looks like +5V.
> >
> > I don't have schematics, and I'm not ready to risk wrecking
> the drives
> > determining the following question: Should the solenoids pull
> in on +5 or
> > +12? If I'm seeing +5, I suspect the solenoid driver
> transistor could be
>
>
> I am not sure quite which version my schematic applies to (it says
> 'FD55(L)' on it), but it appears the head load solenoid pulls in on 12V
> and holds on 5V.
>
> The head load solenoid conencts to the 2 pin connector J4. Pin one goes to
> the open collector driver (part of U8), and is grounded whenever the
> solenoid is 'in'. Pin 2 goes via a diode (CR1) to +5V and via a transistor
> (Q4) to +12V. THe idea is that U8 will ground one end of the solenoid and
> Q4 will be turned on briefly when the solenoid is to pull in (thus
> applying 12V to the solenoid, CR1 being reverse biased now) and then Q4
> turns off (U8 still grounds the other end of the solenoid), allowing it
> to hold in (5V power suppled via CR1).
>
> > cooked. The solenoid coil is intact, as I'm seeing 44 ohms
> across it, out
> > of circuit. In either case, I don't feel even the lightest
> twitch when it's
> > supposed to pull in (and the jumper is in place, for load on
> motor select).
>
> If the solenoid is mechanically OK, I'd suspect Q4 (assuming it's the
> same circuit). If that's OK, then I guess U6 (a custom logic gate array)
> is defective -- it controls the head load circuitry (and a lot of other
> things)
>
> -tony
>
>
Received on Tue Feb 26 2002 - 22:55:39 GMT