On Thu, Apr 27, 2017 at 1:58 PM, Tony Duell <ard.p850ug1 at gmail.com> wrote:
On Thu, Apr 27, 2017 at 6:42 PM, Ethan Dicks via
> (diagnosing and repairing a) TM-100-1 floppy drive...
Floppy drives of that vintage consist of a number of
systems (there's a common enable/drive select but that's about it).
It looks like a problem in the read chain, but is it? If the spindle was
turning at the wrong speed I think it would fail to read.
Yes. I did consider the spindle speed, but I'm reasonably certain it's good.
So I would check each subsection of the drive, just in
case it's not
the obvious one.
Well, yes. I'm really just asking about known weaknesses as a starting point.
In the case of the read amplifier, you could start
with a differential-
input 'scope on the pins used for head alignment (reading a normal
disk). If there's a good signal there the head select diodes (AFAIK
these are present even on the single-sided drive) and first amplifier
IC are OK. If not, then debug that part.
I don't know of any obvious common failures, and
murphy's law will ensure that your drive has something odd failed :-)
Perhaps. The last failure with this unit had the most obvious cause.
I literally tested one component and it was exactly that part that had
> Additionally, for a testing framework...
There are/were drive exercisers but no idea where
you'd find one now.
If you were nearer to me, you could use mine....
Right. I don't have a drive exerciser (and I live in the States) so I
didn't figure that was an easily achievable path. I'm figuring on
having to use a live machine to make the drive dance and I don't fancy
writing my own code on top of it all. Rather than go to that extent,
I'm more likely to toss the drive on the "to be fixed someday" pile
and get to it (much) later.
You need a 'scope to debug the read amplifier of
applies even if you have a drive exerciser).
Yes. Of course I have a scope. At least one.
Do check the spindle speed. Often there is a strobe
disk on the
spindle pulley in these drives
There is. It works.
But also check ('scope) that you are getting 5
per second, just in case the darn thing is running at half speed or
Worth verifying, but there's a visual difference between 300 RPM and
150 RPM (plus they sound different).