15 Sep
2004
15 Sep
'04
8:09 a.m.
On Mon, 2004-09-13 at 08:44, Paul Koning wrote:
John> What can the actual drum clock be... I
dunno... another
John> reason to slow the drum; see below further...
No, don't do that. The heads might not fly if you do that, and you'd
end up with an instant head crash on every head.
As I wrote earlier, they are contact heads, but you are correct, running
them at reduced speed would prevent them from lifting ever, rather than
just the speed up/down time duration.
(The heads are pressed against the platter with a small spring, with a
few grams of force, to counter-act the lift. There's an adjustment
procedure in the hardw. man. for setting it.)
Digitizing at 8 bits, more if you can get it easily,
and minimally 8x
the data clock rate sounds like the way to go. That's clearly more
than the original used. The argument for doing so is that it will
give you a way to recover data that would not be recoverable with the
original electronics.
Agreed. This would be 3-channels of 8-bit at 640Ksamples/sec to get the
timing tracks, or 35-channels for timing+data.
The thing is, after RTFM and this discussion I'm leaning towards
disabling writes, machine bring-up, then record timing tracks as digital
data:
a) I have to spin the platters under the heads (note1)
b) I can reasonably assure writing will not ruin the data.
c) There's a good chance the platter is OK; if not this path
should cause no more harm than any other approach.
(note1: There is a way to recover the data without spinning it, but it's
a little out-there: remove the platter, clean, apply that magnetic fluid
(sic) used to make bits visible, and *optically* make a copy of the
disk. It's not *that* crazy, but it's extremely unlikely I'll attempt
this. The disk is only about 80 bits/inch, it's not too crazy.)
If the timing tracks turn out to be bad, or read amps are off etc, I can
get more exhaustive.