FD400 drive troubleshooting
ard at p850ug1.demon.co.uk
Sun Nov 25 17:08:29 CST 2007
> I got my math wrong. The fellow is also wrong.
> 45/60 = .75.
> 100/.75 = 133.333....
> If rounded to 133, you get 45.11278195----
Incidentally, I asked a friend wbo is both a classic computer enthusiast
and a musician if there would he any audible difference between playing
the record at 45rpm and at 45.11 rpm. He said he didn't believe anyone
could tell them apart. So I susepct the only people this matters to are
Actually I am suprised nobofy has tried to sell said audiophools a
crytal-controlled lamp to view the strob disk with. Or amybe they have
and I've not noticed it yet.
> Still, using Tony's multiple method, 400 dots
> would work fine. It would be a large disk but
> it would work.
It's hardly 'my method'. I certainly don't claim to have invented it, but
alas I can't find a reference to it.
I am not sure when stroboscopes were invented, I susepct they pre-date
electricity, though. Certainly stroboscpinc tuning forks exist -- these a
tuning forkes with slotted vanes on the tines (they are designed to have
the extra mass of said vanes, of course)< you view the stroboscopic disk
(or wahtever) through the slits.
To make this marginally on-topic,such tuning forks were used, at least in
the UK, to set the speed of teleprinter motors. Creed teleprinters have
series-wound motors with a governor assembly on the end of the motor, and
you viewed the black and white stripes on the governor cover through such
a tuning fork.
Somewhere I have a trleprinter test set (an ATE (manfufacturer) TDMS5 if
you know about such things). The master oscillator not only drives the
ring counter that acts as the transmit distributor (the whole thing is
valved, BTW), but also a neon lamp on the panel. You are supposed to view
this lamp trhough one of said tuning forks and effectively 'zero beat'
the bulb agianst the fork to get the oscillator on-frequency.
One other thing to be aware of. The ideal strobosope has very narrow
flashes of light with larger gaps between them. If you are using a
'harmonic disk' (or whatever you want to call it), you need to get closer
to this ideal than for a normal disk (at leat to get a very clear
pattern). Of coure a real xenon-tube strobe does this, a mains neon bulb
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