Calibration of 8" floppy drive?

[Dan K]

>If belt driven ( suspect most 8 incher are ), make sure the pulleys are smooth and clean.
Often old belts will lose a little small lump of rubber that stick to
the pulley. This will cause mis-reads. Make sure the belt is tight and
not slipping.

Hmm I think the pulley mechanism seemed okay, but I'll check for dirt
and make sure the rubber seems to be sitting properly.

>The pressure pad can get lumps on it from disk crud. The pad must be flat. It can not be cleaned with a clear disk that is double sided. Solvents don't work well. I often find a dull knife edge works well to get crusted gunk off.

Is this the fuzzy little pad that is on the end of the plastic
mechanism that pushes down on the disk? I feel like a knife would cut
the fuzzy material, and one of the pads is missing for me (see above)

>The rest, Chuck had stated. Don't mess with tracking or fiddle with pots that you are not setup properly to adjust.

I'd definitely like to avoid that. Especially for any mechanism that
has a paint marking indicating it was calibrated at the factory

-Dan

On 2/5/16, dwight <dkelvey at hotmail.com> wrote:
> If belt driven ( suspect most 8 incher are ), make sure
> the pulleys are smooth and clean.
> Often old belts will lose a little small lump of rubber that
> stick to the pulley. This will cause mis-reads.
> Make sure the belt is tight and not slipping.
> The pressure pad can get lumps on it from disk crud.
> The pad must be flat. It can not be cleaned with a
> clear disk that is double sided.
> Solvents don't work well. I often find a dull knife edge works
> well to get crusted gunk off.
> The rest, Chuck had stated. Don't mess with
> tracking or fiddle with pots that you are not setup properly
> to adjust.
> Dwight
>
>
> ________________________________________
> From: cctalk <cctalk-bounces at classiccmp.org> on behalf of Chuck Guzis
> <cclist at sydex.com>
> Sent: Friday, February 5, 2016 3:40 PM
> To: General Discussion: On-Topic and Off-Topic Posts
> Subject: Re: Calibration of 8" floppy drive?
>
> On 02/05/2016 01:58 PM, Dan K wrote:
>
>> So, how do you deal with your 8" drives, and what do you do when
>> they don't work?
>
> I've got both the FDD-100s and the double-sided cousin, the FDD-200.
> They're very similar in construction; good German engineering, cast
> metal faceplates, etc.  They really should not be drifting out of
> alignment.  Bitsavers has some useful documents on them.
>
> First off, IIRC, these are leadscrew-type positioner drives.  One issue
> dogging these is that grease on the leadscrew can get filthy with dirt
> or harden, preventing smooth operation of the positioner.  Make sure
> that the leadscrew is clean--use a mild solvent such as kerosene if it's
> hardened.  Re-lube with a lightweight grease or oil--you just don't want
> the carriage to "stick" in its travel.
>
> Make sure that the track 0 sensor is clean--the same for the index sensor.
>
> Remember that floppy drive bus topology is open-collector, which implies
> that the "receiving"  (far) end be terminated with a pullup resistor
> (usually 150 ohms to +5 on 8" drives).  Very often, this is in the form
> of a DIP resistor network.  If you're missing it, operation is going to
> be erratic.
>
> Since you're dealing with single-sided floppies, check the condition of
> the side 1 pressure pad--the glue on these often dries out and the pad
> falls off.  The pad itself resembles a billiard cue tip.
>
> Don't get into the alignment issue without a scope and an alignment
> disk--once you loosen the stepper motors, it's a very touchy operation
> getting them back into position, even with a special (expensive)
> alignment disk.
>
> Hopefully, this will get you started.  Just remember that dirt in any
> disk drive is the Devil's playground.
>
> --Chuck
>
>
>
>