RL02 Disk Cartridge Problems

From: Patrick Finnegan <pat_at_purdueriots.com>
Date: Mon Dec 2 22:45:00 2002

On Mon, 2 Dec 2002, John Lawson wrote:

> I'm not sure what the hardware timeout for bad Tachometer signals is...
> but it sure sounds like either the tach segment is munged somewhow (The
> ring on the bottome of the platter hub with the slits cut in it) or that
> the data on the platter is damaged, or that it was not written on a DEC
> system. The packs were used on a number of different systems.

I'd go for possibly a dislodged "tach magnet" (really they mark sectors
IIRC). I'd _really_ doubt it's got anything to do with what's written on
the pack (see below).

> With deference to further incoming opinions, I would think perhaps the
> data format is completely incompatible, and the drive can't 'find' the
> correct bit pattern, and thus it pukes. Tony Duell is familiar with the
> internal operation of the RL02, and perhpas he can shed better light.

While I'm not Tony, I spent some time last year slaving over the RL02 (and
RLV12, RL8A) printsets, and I can tell you that the drive _doesn't_ care
what data is recorded on the disk. Fundamentally, the RL01/02 is a
fairly 'dumb' drive. Other than the sector marking magnets on the hub of
the disk, the drive is fairly undiscriminating. The only real circuits
between the read/write head and the ports on the back of the drive are
read and write amps (and write gate, etc).

A good check would be to listen for the heads to load into the pack. If
they're not loading, then there's no way that the data can be the source
of the problem.

Purdue Universtiy ITAP/RCS
Information Technology at Purdue
Research Computing and Storage
Received on Mon Dec 02 2002 - 22:45:00 GMT

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