Calibration of 8" floppy drive?

Dan K 100dashsix at
Sat Feb 6 23:50:42 CST 2016

It figures: after all this talk about neither of the drives working, I
plugged one of them in (the one that's in better condition) and it now
recognizes the disk. The felt pad presses on the media, at least very
lightly, and perhaps this is the source of the main problems in the
other drive.

Other issues I didn't mention: the metal front panel that prevents the
disk drive from opening too far is broken on one of them, and the
latching mechanisms on both drives don't work, so that I have to wedge
something on top to keep the disks engaged. I also haven't tested the
reliability of the drives, as in writing a ton of data and verifying

I noticed you changed the destination to cctech instead of cctalk,
James. I'll try to do that in the future for on-topic-only
discussions, as I suspect that's the custom here.


On 2/6/16, Dan K <100dashsix at> wrote:
> One interesting thing I noticed (and I'm investigating at this very
> moment) is the arrangement of the head load armature. A spring-loaded
> arm will swing down and push the felt pad against the media, which
> brings it into conformity with the head. However, there's a little
> thing on the lever that touches the plastic head load mechanism that I
> posted links to earlier.
> When the head load solenoid is retracted, the felt pad arm is lifted
> up enough that the disk can slide in and out freely. When the head
> load solenoid fires, the whole thing comes down and it's clearly
> supposed to push on the media. However, I think in both my drives it
> doesn't touch it, or if it does it only barely touches it. I'm
> thinking perhaps the armature has to come down further.
> That being said, at least once I tried doing that, manually letting
> the arm come down, and it didn't improve the observed behavior. It's
> possible something else was happening then too, so I'll retest.
> -Dan
> On 2/6/16, James Attfield <james at> wrote:
>>> Date: Sat, 6 Feb 2016 00:46:33 -0500
>>> From: Dan K <100dashsix at>
>>> To: "General Discussion: On-Topic and Off-Topic Posts"
>>> 	<cctalk at>
>>> Subject: Re: Calibration of 8" floppy drive?
>>> Message-ID:
>>> 5A at>
>>> Content-Type: text/plain; charset=UTF-8
>>> Are there any good alternative solutions I can do to replace it? I'm
>>> sure I don't want the plastic touching the disk media.
>>> -Dan
>> Seems like eons since I learned to align PerSci 299B's with Dysan
>> alignment
>> disks and 'cat's eyes' on a 'scope :)
>> I echo the other sentiments here - do NOT undo or unscrew anything
>> relating
>> to head positions especially involving allen (hex) screws unless you have
>> a
>> 'scope, an alignment disk, a very good quality set of hex screwdrivers
>> (keys
>> will normally NOT suffice) and a modicum of experience. Granted, lead
>> screw
>> single-headers are a little easier to do than voice-coil double-headers
>> but
>> if you don't have to get into it then don't - explore all other options
>> first.
>> I'm afraid my TM-848's are double headers so the top head provides the
>> pressure but back when the drives were single headed felt pads did the
>> job
>> of the second head. The tension was provided by the spring, the pad just
>> prevented scoring. I do NOT speak from experience BUT if I had to use
>> anything the kind of small felt pads you can get from hardware stores
>> (e.g.
>> B&Q in the UK) seem remarkably similar in composition and would be worth
>> a
>> try especially if you have one original to compare. Cut to shape, most
>> are
>> self-adhesive too - bonus.
>> HTH
>> James

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