Date   : Thu, 14 Feb 2002 00:28:18 GMT
From   : pete@... (Pete Turnbull)
Subject: Re: BBC Micro repairs

On Feb 13, 23:27, endie wrote:
> When did you last use these disks, and where were they stored?  The odds
are
> that you do indeed have a perfectly functional drive and beeb, but the
disks
> were corrupted years ago.

If there are several disks involved, and they all give similar errors, and
all the time, I'd say that's unlikely.  It takes a lot to corrupt a disk;
dropping a small fridge magnet on one won't usually do any harm, for
example.

Is it possible that they're ADFS disks and you're trying to read them using
DFS?  Or vice versa?  Are they 40-track disks in an 80-track drive (or
v.v.)?  Common symptom of 40-track disk in 80-track drive is that you can
read the catalogue (if it's DFS, not ADFS) but almost anything else gives
an error.  Common symptom of the opposite is that you can't read anything
(though sometimes, depending on the drive, you might be able to read the
directory of a DFS disk).  Is the ribbon cable securely connected at both
ends?  Any break in the cable?  Are the voltages to the drive (+5V and
+12V) up to par?  No bad connections?

If you always get an error message after the disk seem to try reading a few
times, it may be alignment, corruption, cable fault.  If it just spins and
possibly times out eventually, it's probably wrong combination of
disk/drive/filing system or a broken cable.

> Alternatively, and this is less likely, the head alignment is wrong,
> particularly if these disks were created on another drive.  Sadly, the
> odds against you adjusting this to get it right is expressed as a number
> tending towards the sqaure root of zero.

Well, yes, unless you have right tools, in which case it's fairly easy.
 You need an alignment disk and an oscilloscope, which any competent
repairer who deals with disk drives will have.

Other "mechanical" things that go wrong with drives apart from alignment
are the track zero sensor, and, less commonly, dirty heads.

-- 
Pete                                           Peter Turnbull
                                               Network Manager
                                               University of York