Re: Happy as a clam

["Michael J. Mahon" <mjmahon@aol.com>]

Wayne Stewart wrote:
> Today I took an antique tube radio down to this radio museum to see
> about repairs. During the discussion my interest in Apple IIs came up
> and the fellow asked me to go with him into the back. There sat a II+
> in the original box with a disk II in the original box. A fairly late
> model RFI II+  that came with the usual books and cards but also
> number of fliers from the period and a ROM card with Integer basic &
> the pre-autostart monitor ROM.
>
> Had a problem with the floppy drive. Something on the Disk II card is
> blowing ULN2003 chips in the drives analog card. I think maybe I'll
> cut my losses and ditch the floppy controller. Maybe keep the PROMs
> though. I know I've got a box of Disk II cards somewhere.

The controller only switches sections of the ULN2003 off or on.
If that causes it to blow out, then there must be:

1) a problem with the seek stepper motor that causes it to draw
   too much current;
2) a short in the cable that keeps one or more phases of the
   stepper on continuously; or
3) an IC failure on the controller that keeps one or more phases
   of the stepper on continuously.

In case 2) and 3), the stepper motor should be getting pretty
warm, too.  If in 1) a stepper phase is shorted, then energizing it
will blow that section of the ULN2003 and the stepper motor may not be
getting warm.

> Maybe I was too happy. It was after 10 PM before I realized I'd
> forgotten about supper.

That's a good day!  ;-)

-michael

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