5 Oct
2011
5 Oct
'11
7:18 a.m.
From: ard at p850ug1.demon.co.uk
Subject: Re: shipping magnetics
To: cctalk at classiccmp.org
Date: Tue, 4 Oct 2011 20:45:03 +0100
Hi Tony
No, once I determined the problem, I moved the monitor away and
reformatted the disk.
I didn't means a bias signal, I was thinking more a magnetic offset
to the signal.
Dwight
I did enough experiments to see that I had no
problems reading floppies
other than those that were recoreded near the monitor.
OK. I ssume areas of the disk that were not written near the monitor were
unaffected.
My guess is that it upset the bias so that it
shifted the depth over time=
There's nop bias (in the normal magnetic-recording sense of an HF
oscillation) in disk deives (and they use DC to drive the tunnel erase
head too). I wonder if somehow, in the presense of the normal write
field, the alternating field from the monitor was recorfed, causing extra
transition...
I don;t suppose you still have such a disk? If so, it would be
interesting to see what a efective track contains, both at the output of
a normal floppy drive trying to read it, and as an analgoue signal at the
putput of the read amplifier.
-tony