16 Jan
2005
16 Jan
'05
5:56 a.m.
Qume drive working, but don't know where to go
next. I
guess I could swap
the boards between the two units, but that'll
only tell me if it is
electronic or electro-mechanical.
Other than that, any suggestions for figuring out if it is
alignment, broken
sensor, or something electrical?
The alignment adjustments, in general, are what are known as
'interchangeability adjustments'. In other words, if they're
a bit off,
the drive will be able to format, read, and write its own disks, but
those disks will not be useable on other drives, and vice versa.
So what you do first is to hook the drive up as B: and try
formatting a
blank disk in it. Note that if, for some reason, the machine
thinks it
only has one drive, it'll map A: _and_ B: to that drive.
You'll get some
obvious messages if this has happened, in which case the problem is
certainly not just alignment. same diskette put back in the working drive formatted
to 360K. So, how do
these drives tell if they're dealing with SS vs. DS meadia? Does it just
look for a signal from the second head? Is there another sensor that
indicates "yep - double sided". This is how it works with 8" drives. The
index hole is in a physically different spot.
Unlike the 8" drives, there is no signle/double sided signal on the 5.25"
drive interface connector, and there's no sensor for anything like that
(I looked at the schematics this morning, they look pretty standard,
there are 3 sensors for index. write protect, and track 0).
My guess is that either :
a) The side select signal does nothing due to a logic fault in the drive,
and that therefore when it tries to read the second side, it gets the
data from the first side. A true signle-sided drive would do this.
b) There is no useful signal from the side-1 head (this is the head on
the top surface of the disk, of course), either because the head is
dirty/defective, or a damaged connection back to the logic board, or an
electronic fault on the board. I am not sure what the software would do
under those conditions -- by rights it should give errors for every
sector on side-1, but it's possible it then assumes the media is really
single-sided, and formats it accordingly.
I think i will have to grab the schematics and see if I can talk you
through the circuitry.
in. Any tips based on the schematic would be of help.
Since all I have at
the moment is a DMM and a homemade logic probe, my tools are lacking to
fully solve this problem.
Well, although _now_ I have some very nice test gear, I debugged my first
homebrew computer (This was when homebrewing meant soldering chips to
stripboard and wiring everything up, not pluging a video card into a
motherboard) with an anlaogue multimeter and an LED+resitor 'logic
probe'. So it certainly _can_ be done...
-tony