FD400 drive troubleshooting - test-drb@ccmp.vtda.org

25 Nov 2007

---------------Original Message:
Date: Sat, 24 Nov 2007 10:02:54 -0800
From: dwight elvey <dkelvey at hotmail.com>
Subject: RE: FD400 drive troubleshooting

...
   From: dm561 at
torfree.net  ------------Original Messages:
>> Date: Thu, 22 Nov 2007 12:17:31 -0800 (PST)
>> From: Fred Cisin
>> Subject: Re: FD400 drive troubleshooting
>>
>>>Many/most drives have 50Hz/60Hz zebra discs on the flywheel, for using a
>>>flickering fluorescent light.
>>
>> Which just happens to be the ratio of 300RPM vs 360RPM, so that on a 300RPM
>> strobe disk w/a 60Hz light the 60Hz bars = 300RPM and the 50Hz bars = 360RPM.
>>
>> FWIW,
>
> Hi
> I think you have the ratio backward. The 60 Hz disk for 360 RPM
> can be used for the 50 Hz 300 RPM.
> Dwight
>
> ----------Reply:
> Well, unless you're just saying that a 60Hz 360RPM strobe disk (if you had one)
> would also sync at 300RPM under a 50Hz light, I don't see what's backward.

...
 Hi
 That is what I said. The disk with 20 bands would work for both
a 360 RPM and 60Hz light or a 300 RPM and 50 Hz light. --------
Gee, I thought that was what *I* said (and you claimed was backward).

Let's see; I said that 300RPM @ 50Hz = 360RPM @ 60Hz, and you 
said that's backward - 360RPM @ 60Hz = 300RPM @ 50Hz.
Sounds like the same thing to me (and Tony) except that a 360RPM
strobe disk is a lot harder to find than a 300RPM.

Sheesh...
---------
...
  Tony mentioned that one could increase the number of
bands for the
problem of the 50Hz with a 360 RPM drive. It makes sense. --------
Indeed; glad to hear it.
-------
...
  Tony mentioned that most 8 inch drives were speed
controlled by
the mains and as long as the belt was in good shape, using a strobe
wasn't much needed. -----
You really should read more carefully; he didn't say "most," he said
"all of mine," referring to his particular collection. In fact, many 8"
drives 
were 24VDC powered, including the Pertec FD400 which prompted
me to send (and regret) the original post that started this bizarre exchange...

m