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<DIV>Hi George:</DIV>
<DIV> </DIV>
<DIV>I really appreciate your sharing all these great stories! The
experience on this list is amazing, and I look forward to hearing lots
more!</DIV>
<DIV> </DIV>
<DIV>My post about changing the speed of the capstan was referring to your
description of what was done to the pulleys on VR-2000 or 1200 machines.
Unless I'm missing something, that would change the tape speed, which in turn
changes the video track specifications.</DIV>
<DIV> </DIV>
<DIV>My guess is that the pot you are talking about is 13R19 which,
depending on where you look, is alternately called either "Capstan Sensitivity"
or "Capstan Damping". You adjust it by disturbing the capstan during play
and and observing how much it "bounces" in recovery.</DIV>
<DIV> </DIV>
<DIV>Regarding Intersync, you probably know that there were a number of
revisions to the design thru the years, especially in the capstan servo.
In '66, board 14 was added to the servo system. In '68, boards 9 &10
were completely redone with new circuitry utilizing IC's. There were
other, but less drastic changes to bds 11, 12 & 13. So, to some
extent. experience with these probably varies depending on the version in
use.</DIV>
<DIV> </DIV>
<DIV>
<DIV>Neat story about the "alternate applications" for the triac
controls!</DIV></DIV>
<DIV> </DIV>
<DIV>Don</DIV>
<DIV> </DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=georgenann@aol.com
href="mailto:georgenann@aol.com">georgenann@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=quadlist@quadvideotapegroup.com
href="mailto:quadlist@quadvideotapegroup.com">quadlist@quadvideotapegroup.com</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, January 26, 2010 12:52
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [QuadList] Cap Disc</DIV>
<DIV><BR></DIV><FONT face=arial color=black size=2>
<DIV style="FONT-SIZE: 10pt; COLOR: black; FONT-FAMILY: helvetica,arial">
<DIV id=AOLMsgPart_2_9a3555a3-3d06-4045-a09a-7e39b3520bf9><FONT face=arial
color=black size=2><FONT face="Arial, Helvetica, sans-serif"></FONT><FONT
face="Arial, Helvetica, sans-serif"></FONT><BR><BR>
<DIV style="CLEAR: both">Whoa!! Hold on, guys,</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">I never said there was any speed change in the
capstan at all. The disc is only the freq. loop in the cap
circuit. The phase comp is sill there and does such a great job you
don't even need the disc. Actually I think they would fight each other
in the beginning which is why it takes a little less time to lock up without
it. It creates no time changes at all and all the tracks are scanned as
they should be.</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">My <U>guess</U> is that this effect might be
demonstrated by listening to the head when you first hit "Ready". I
notice that the head seems to come up a little fast at first, then locks up at
approx. the proper speed. At first it is somewhat out of control, then it
locks up to the proper phase. This may well be what happens in the cap
servo when both the disc. (freq) and the phase control (phase) are both
working. I always wanted to eliminate the head disc. but never got
around to doing it. You can also see the cap error voltage hunting a bit,
especially if the cap osc is a little off freq. You might notice that it is
the phase comp which switches to the various refs. while tape is rolling,
(Vert or H or ref).</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">I'm sorry I didn't pick up on this on your earlier
e-mails.</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">How you can make 2 tapes at the same time and still
come out with 2 good recordings a couple seconds apart is beyond me, without
having any kind of AST or DT. The only thing I can think of is that on
the AVR-2 the digital TBC may have made up for a slight difference in cap
speed, due to it's wide window and there may have been a frame or 2
missing that nobody noticed.</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">By the way, the take up and supply servos in the
AVR-2's was neat. The output of the servo system was an optocoupler in
which an LED lit up a light dependant resistor. This ldr was
connected to the control terminals on a block containing a triac and it's
phase shifting network (all embedded in epoxy). I think this block was made by
Cutler Hammer, (I may be wrong, but who cares). The triac terminals went in
series with the 110vac take up and supply motors and controlled the torque as
needed, either holdback or full bore in rewind or FF.</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">These blocks were kind of expensive, CBS
ordered many or them and they were all used, although I can't remember
replacing any of them in AVR-2's. They made great motor controllers for
electric drills, florescent dimmers, soldering iron controllers, etc. All
you had to do is put a 200K pot across the control terminals, where the ldr
was connected for full control, and the AC in series with the two other
terminals.. I can't imagine where they all went!! Also, CBS ordered many
200K pots for some reason.</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">Insofar as the cap pully mod is concerned, look
at the intersync schematics, there is one pot called "Cap servo gain" or
something to that effect, I don't remember the number. IF you bring this
pot up a little too high the cap will go nuts and at the same time you had to
set it very carefully, especially if you wanted to make good edits. This
was because of the cap fighting the servo, apparently the change in the speed
from mono to color was enough to upset it. The new cap speed made a big
difference. While the servo probably had a good range, it may have been
kind of close to one end of the envelope. Also, now that I think of it
that pot wasn't one of the "normal" tweeks you would adjust, only if you were
doing a "long servo setup".</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">73,</DIV>
<DIV style="CLEAR: both"> </DIV>
<DIV style="CLEAR: both">George Keller</DIV></FONT></DIV><!-- end of AOLMsgPart_2_9a3555a3-3d06-4045-a09a-7e39b3520bf9 --></DIV></FONT>
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