[Coco] Disk Drive FD 501 Floppy

[Gene Heskett]

On Monday 15 April 2019 02:33:04 Arthur Flexser wrote:

> Gene, why would bad capacitors improve after 25 minutes of operation,
> a is the case here?

ESR often drops with an elevated temp in the caps.
>
> I'd have figured that that was a sure sign of a lubrication problem,
> with dried up lubricant softening after a while with the heat of
> operation.

You could well be right Art, at its age that lube has got to be both 
badly contaminated, and at least as hard as a cold crayon by now, So a 
quart of paint store alcohol and half a box of q-tips (never re-wet a 
q-tip, toss it and get a clean one) followed by re-application of auto 
chassis grease might be just the ticket.  If its a spiral screw driving 
the carriage, make sure the spiral is clean all the way to the bottom of 
the groove the wire rides in. Ditto the rods the carriage slides on, 
make them lox clean then re-lube. Light oil can be used, but I find the 
drives are markedly quieter if the rods have an invisible coat of 
chassis grease instead, and it will likely outlast the oil. Something 
like wd-40 might work but it dries to a wax coating in a day or so, 
which isn't a great lube.

Thanks for the reminder that it could be mechanical.

> Art
>
> On Mon, Apr 15, 2019 at 1:59 AM Gene Heskett <gheskett at shentel.net> 
wrote:
> > On Sunday 14 April 2019 23:17:59 Melanie and John Mark Mobley wrote:
> > > If I let my floppy drive warm up (stay turned on for 25 minutes)
> > > then I can boot OS9.
> > > If I do not let it warm up then it hangs after two lines of "..."
> > > dots. What could be wrong with my 501 floppy drive or 501 floppy
> > > controller? If I turn off the computer but leave on the floppy
> > > drive for a cool down time, then turn the computer back on it will
> > > work just fine.  So the problem is with the floppy drive or floppy
> > > controller. Another time we swapped out the floppy drive and that
> > > fixed it, so that narrows it down to the floppy drive.
> > > How many parts make up the floppy drive?  Power supply, Floppy
> > > drive 0 & 2., Floppy drive 1 & 3, and ribbon cable.
> > > The ribbon cable is new.
> > > Should I swap floppy drive 0 & 2 for floppy drive 1 & 3?
> > > What adjustments can be made to floppy drives?  Fix the power
> > > supply, belt, rpm, head alignment, ...
> > > Can I get it repaired at the CoCoFEST?
> > >
> > > John Mark Mobley
> >
> > I am a C.E.T. At their advanced age John, and the symptoms you
> > describe, my bet is on the physically big filter caps in the supply
> > being "dried out". This causes a loss of capacitance, and a rise in
> > the ESR. ESR is equivalent series resistance, generally caused by
> > oxidized connections between the foil of the capacitor, and the
> > terminal you see coming out of the bottom where the wires are
> > soldered on.
> >
> > Disassemble it to where you can see them, and if the tops of the
> > cans are bulged, (generally indicating high ESR which causes
> > heating, which may get better at higher temps) or the base shows any
> > whitish leakage, replace them with more modern equivalents for
> > voltage and capacity.  You can generally go up in capacity, but not
> > down in voltage unless they are 35 or 50 volt parts now, in which
> > case you can go down to 16 volts as the supply for the motors is 12,
> > and there's generally a regulator to make 5 for the drives logic. It
> > may have a smaller cap on its output, in which case replace it too. 
> > The capacitance is not super critical, but the ESR is.
> >
> > But few test meters can do a decent job of measuring ESR. The best
> > one (the Capacitor Wizard) is $200 or more. If any doubt, replace.
> >
> > Generally, an electrolytic capacitor will stay "formed" longer if
> > they are being operated right at their nameplate voltage, but caps
> > marked 6.3 and 16 volts so they are in the top 30% of their voltage
> > rating will work and almost as long. A 50 volt cap, in a 5 volt
> > circuit, has got to be about dead by now.
> >
> > If you aren't handy with a soldering iron and rosin cored solder and
> > own a solder sucker, there are several on this list who are.  And
> > are probably within a Saturday trips driving range, I am not.
> >
> > Take care you two.
> >
> > Cheers, Gene Heskett
> > --
> > "There are four boxes to be used in defense of liberty:
> >  soap, ballot, jury, and ammo. Please use in that order."
> > -Ed Howdershelt (Author)
> > Genes Web page <http://geneslinuxbox.net:6309/gene>
> >
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > https://pairlist5.pair.net/mailman/listinfo/coco


Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Genes Web page <http://geneslinuxbox.net:6309/gene>