[QuadList] Capstan Information

[Dennis Degan]

		On Sep 24, 2014, at 11:54 PM, John M wrote:

> Just as an aside, Don, we found playing back a tape from a 3000 on a 2000 required the use of non standard tracking on the intersync - this was the case for all 6 of our 2000's. Our Avr1 and AVR 2 just played it - what was the go here?

		I answer:

	Playback with 'non-standard tracking' indicates to me that the VR-3000 record machine's CT head was not in standard alignment.  AVR-1s have a wide latitude on CT alignment while playing a tape, much wider than any VR machine.  In fact, it was the only machine capable of playing a tape with NO CT at all (it used RF peaking to track the tape).  Manual tracking was not needed on the AVR-1.  It could automatically find peak RF from the playing tape no matter what.  The AVR-2 had a more advanced servo system so it also had a wider CT range, but it operated quite differently from the AVR-1's vacuum capstan.
	'Tracking' refers to the relationship between the CT pulses and the transverse video tracks' locations on the tape.  Since the CT head is placed ahead of the spinning video heads, there is a specified standard for the distance between the two (I forgot the exact spec, sorry).  Turning the tracking knob advances or retards the playback phase of the CT.  This function allows the accurate manual alignment of the video tracks over the spinning video heads during playback in order to maximize RF.  Your VR-3000's CT head was out of spec, requiring the VR-2000 playback machines to be operated in 'non-standard' tracking mode.  This essentially provided the VR-2000 playback machines with a wider range for tracking adjustment, something that the AVR-1 and AVR-2 machines didn't need.

			Dennis Degan, Video Editor-Consultant-Knowledge Bank
					    NBC Today Show, New York


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