24 Aug
2004
24 Aug
'04
11:38 a.m.
I have a TRS80 Model 12 that's been upgraded to a 16B (with two 8"
slim-line floppies). I am trying to copy some discs but not having much
joy.
One theroy is the media is cactus.
The other theory is that following some reading about these machines,
because of the size of the drives they tended to get out of alignment
regularly. How do I check alignment on the old classics.
Take a known-good blank 8" disk and format it on one of your drives. If
you can then read/write to it in that drive without problems, then the
only thing that could be wrong with the drive is the alignment. If it
fails, then you have other problems with the drive.
To check the alignment properly, you need a CE (Catseye) disk and a
'scope. Basically the disk has a special patern recorded on it (this
cannot be copied using a normal drive, BTW) and you look at the outputs
of the read amplifier with a the 'scope. You see a pattern of 2 lobes on
the 'scope screen -- if they're the same height the head is alighed, if
one is larger than the other it's offset from the correct position.
It's not hard to do, but the Catseye disk is expensive (I am still
looking for the 8" and 3" ones, BTW...).
My experience suggests that head radial alignment is not normally a
problem unless you've replaced parts of the drive. More likely is a dirty
head (you have cleaned it, right? With a cotton bud dipped in
propan-2-ol, not one of those useless cleaning disks), a worn-out head,
other mechnaicl problems, or an electronic failure.
-tony