[Coco] Disk Drive FD 501 Floppy

[Arthur Flexser]

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

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.

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