28 May
2008
28 May
'08
1:15 p.m.
On Tue, 27 May 2008, Tony Duell wrote:
That threw me as well. There must be a misprint somewhere, since the unit
works just fine when I substitute a known-good 2793 from another drive.
I have checked the WD279X data sheet, and that pin is certainly
active-low. It's shown with a bar over it on the pinout diagram and in
the table of signals, it's also descried (under the 'Restore' command)
as being asserted when low.
Now, I suppose it's possible that your defective 2793 had a short from
this pin to Vcc, so that the track0 senosr circuit couldn't pull it low.
That would make it test high all the time. But if it's low normally, goes
high when the head is on track 0, and yet a new 2793 fixes the problem, I
don't know what the heck is going on.
-tony
Anyone have experience with these? I have a defective unit (purchased on
eBay - sad story) that tries to bash the drive head to death against the
Track 0 stop when turned on. I picked up the service manual and
schematics and was able to verify that the Track 0 sensor was working and
that that NTRACK00 (pin 34) on the 2793 FDC chip is pulled high at that
point.
I don;t have the data sheet in front of me (and I certainly don't haev
the 1050 schematics here), but if that signal name 'NTRACK00' means the
obvious thing, it's _not_ Track0. In other words it should be low when
the head is on track0.