TEC FD-50x drives - known issues?
joseph c lang
jclang at notms.net
Sun Oct 9 16:21:53 CDT 2005
On Sunday 09 October 2005 08:34, you wrote:
> > >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 :-)
> 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.
> > >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.
> 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?
> > 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.
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.
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