Date   : Sat, 24 Sep 2005 19:40:48 +0100
From   : "Helen & John Simpson" <helenandjohn.simpson@...>
Subject: Re: Strange 51/4" drive fault

> >Basically the head is able to move towards the centre of the 
> >disc, but 
> >it doesn't like going back the other way. The motor buzzes 
> >and the head 
> >struggles to move. I tried lubricating the slides, but this didn't 
> >help.
> 
> The step rate is too fast and the drive can't cope with it.
> 
> If you're using a BBC and it has switches or wire links 
> fitted to the bottom right of the keyboard PCB, make sure 
> links 3 and 4 are OPEN.
> 
> If you're using a Master, type *STATUS and look for the 
> FDrive setting. I bet it's set at 3.  *Configure Fdrive 5, 
> ctrl-break and try again.

Amazing! It works! That explains everything.

I changed the setting myself when I fixed the CMOS battery, in an
attempt to "tidy things up". I must have then used 80T disks for a while
and so not noticed the problem. The problem arose when using some fairly
old and dodgy 40T disks, so I naturally assumed the drive had gone
wrong...

It was Fdrive 7 actually, but I think that is the same as Fdrive 3 in
respect of step rate. Fdrive 5 works fine.

Moral: do not tinker with things that are working.

Cheers

john