Date   : Thu, 14 Feb 2002 07:11:58 +0000
From   : John Woodgate <jmw@...>
Subject: Re: BBC Micro repairs

Pete Turnbull <pete@...> wrote (in <10202140028.ZM9261@
mindy.dunnington.u-net.com>) about '[BBC-Micro] BBC Micro repairs', on
Thu, 14 Feb 2002:
>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.

It isn't impossible that one or two have been corrupted by loudspeaker
magnets, but not all of them.
>
>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.

Yes, all behave similarly.
>
>Is it possible that they're ADFS disks and you're trying to read them using
>DFS?  

No, they are DFS, but a mixture of Watford and Acorn format.

>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). 

No, these are switchable 40/80 track drives and neither mode works.

> 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?

No problems there. I'm an electronics engineer, but I don't 'do'
computers, not even Beebs.
>
>If you always get an error message after the disk seem to try reading a few
>times, it may be alignment, corruption, cable fault.

That seems to be the case.

>  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.
>
They were made on these drives, but something could have happened since.
I also have a card in my A5000 for connecting an external 5.25 drive,
but that won't read the discs either, so the problem may lie in the
drive box.
-- 
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk 
Eat mink and be dreary!