help! shugart 801

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Tue Jul 22 17:58:00 2003

> You may be right but the head isn't even loading so I'm not even getting
> that far. I have a Shugart 800/801 manual but it's vague about the
> differences between the two. But IIRC the 801 is designed to handle hard
> sectored disk and the 800 doesn't. I'm wondering if the index pulse
> detection circuit is different and may be causing a not ready condition or
> something similar. (Yes I know I can check it with a logic probe but I

I think you might well be on the right track. IIRC, the 'ready' signal
only goes active after the index signal has behaved correctly (indicating
there is a good disk, rotating correctly, in the drive). It's possible
that if the drive is set for hard sector operation and you've loaded a
soft-sector disk, then the drive will never go ready.

According to the scheamtics, there's a pair of jumpers labeled '800' and
'801' on older versions of the main PCB. Later versions (with a 40 pin
ASIC) have a single 3 pin jumper with the 2 positions labelled '800' and
'801'. This is confusing, you _don't_ set the jumper to '801' if you have
an '801' drive.

Rather, '800' means soft-sectored (and disables the hard-sector
circuitry, which is only present in 801 model drives), '801' means
hard-sectored. I'd check the position of this jumper.

-tony
Received on Tue Jul 22 2003 - 17:58:00 BST