9 Oct
2005
9 Oct
'05
2:21 p.m.
On Sunday 09 October 2005 08:34, you wrote:
One of the problems with this list is that it's impossible to know the
knowledge/skill level of the person asking the question.
Your original question did seem to suggest you thoguth of the floppy
drive as a single unit, whereas as we both know, it's a collection of
several systems. It certainly helps if we both know which of those
systems is the problem.
Ah, right (or is that Ah... Write :-)). Can you identify the read
amplifier chain (often using NE592 ICs), or is it hidden in an ASIC.
In the latter case, look for a pair of LC filter networks connected to
the ASIC. The read chain almost always consists of differential
amplifiers right up to the final comparator stage, so you expect filters
to come in pairs, etc. If you can find a pair of test point pins
associated with those, then they're almost certainly the outputs you'd
use for head alignemt. Hook a 'scope with differential inputs to those,
try reading a normal disk (never put an alignment disk into a dodgy
drive!). Do the signals look at all sane?
That fired a few brain cells that haven't been active for a long while...
Oh yeah..that's a common problem caused by the small inductors
in the read amplifier going open. too much stress on the leads.
Add a couple of years and bingo no read.
joe lang
A disk drive performs several different functions. In
particular, it
rotates the disk, it detects the index hole and write protect notch, it
moves the heads between cylinders and detects the track0 position, and
it actually does the reading and writing.
This much I actually know :-) Do you
know which, if any, of these systems are working? Can you get the
disk to spin? Do you get an index pulse? Can you get the head to move?
And so on.
All functions appear to work (Motor, Index, Step) - problem in all cases
is in the read/write circuitry. Drive goes through all the motions, it
just can't read/write. It may come to this - At least I do have a couple
of working drives
that I can compare signals with - but I asked in case a) someone has
the technical documentation or b) someone might say "oh yeah, thats
a common problem caused by xxx...", either of which could save me a
lot of time.
I don't know how complicated these drives are, but I can't believe it
would tkae more than a day to figure out the read amplifier section, even
if it is hidden in the ASIC. Sometimes it's quicker to just sit down and
have a go :-)
I think I agree with Allison however that these
drives are crap, and
I'm not sure I want to spend a lot of time on them if suitable
substitutes can be found - in this case, the physical constraints make
this a but more challenging.
Well, I like to keep my machines as close to original as possible.
-tony