[QuadList] Servo Modes

Thu Aug 23 23:50:11 CDT 2012

Excellent description and I agree. The AVR-1 and ACR-25 performed the fast (200 ms lock) regularly. I also agree the two main issues seemed to be the no pinch roller vacuum capstan and the wide TBC (binary switched glass delay line TBC)
Also related to a similar thread we (an independent station with no network spot support) ran our only ACR direct to air for many years. It was something us techs were very proud of.
So......speaking of proud....it is absolutely amazing what engineers did 30 to 40 years ago with no  operating systems to take advantage of. Three developments to think about are the above fast lock VTR's; the Chyron and the ADO. I think most of this using massive TTL logic?
Someone can back me up here but I think the ADO had a 200 Amp 5 volt supply to run all those chips. The Chyron and ACR (logic bay) even did all this with wire wrap on the chips (I think)

Sent from my iPad
Wayne Watson
Calgary Canada
Wayne.watson at sait.ca<mailto:Wayne.watson at sait.ca>

On 2012-08-23, at 7:13 PM, "sgw1009" <sgw1009 at earthlink.net<mailto:sgw1009 at earthlink.net>> wrote:

This is somewhat reminiscent of the AVR-1 and its startup procedure.  When
rolled, the AVR-1 would near-instantly start playing the tape at full speed
(possible because of its vacuum columns and low-inertia pancake capstan
motor).  During this brief period it would look for a reference pulse from
the tape.  Once it retrieved a reference pulse from the playing tape, it
would then know how far ahead or behind the tape was from house reference.
It would then (generally) accelerate the tape the amount (and duration)
needed to make the next reference pulse coincident with house reference.
The wide-window TBC took care of the rest.  This resulted in virtually an
instant roll, although in reality it was about 2 to 3 frames.  This was not
noticeable or objectionable (to the home viewer) during normal program
content, but you could hear the servo working to align the tape reference
with house reference when rolling a tape containing bars and tone.  That is
to say you would hear normal tone, followed briefly by tone that was an
octave higher (sync phase), followed again by normal tone.  Pretty amazing
stuff !!

Steve Walton

 _____

From: quadlist-bounces at quadvideotapegroup.com<mailto:quadlist-bounces at quadvideotapegroup.com>
[mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of Norman Hurst
Sent: Thursday, August 23, 2012 8:04 PM
To: Quad List
Subject: Re: [QuadList] Servo Modes

The Dischert invention was demoed to lock in less than 6 frames from the
time you pushed play.  That's 200 ms.  It was amazing.

The figure on the first page of the patent shows the acceleration profile
relative to house reference.

<http://www.google.com/patents?id=K043AAAAEBAJ&printsec=abstract&zoom=4#v=on
epage&q&f=false>
http://www.google.com/patents?id=K043AAAAEBAJ&printsec=abstract&zoom=4#v=one
page&q&f=false

This is somewhat reminiscent of the AVR-1 and its startup procedure.  When rolled, the AVR-1 would near-instantly start playing the tape at full speed (possible because of its vacuum columns and low-inertia pancake capstan motor).  During this brief period it would look for a reference pulse from the tape.  Once it retrieved a reference pulse from the playing tape, it would then know how far ahead or behind the tape was from house reference.  It would then (generally) accelerate the tape the amount (and duration) needed to make the next reference pulse coincident with house reference.  The wide-window TBC took care of the rest.  This resulted in virtually an instant roll, although in reality it was about 2 to 3 frames.  This was not noticeable or objectionable (to the home viewer) during normal program content, but you could hear the servo working to align the tape reference with house reference when rolling a tape containing bars and tone.  That is to say you would hear normal tone, followed briefly by tone that was an octave higher (sync phase), followed again by normal tone.  Pretty amazing stuff !!

Steve Walton

________________________________
From: quadlist-bounces at quadvideotapegroup.com<mailto:quadlist-bounces at quadvideotapegroup.com> [mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of Norman Hurst
Sent: Thursday, August 23, 2012 8:04 PM
To: Quad List
Subject: Re: [QuadList] Servo Modes

The Dischert invention was demoed to lock in less than 6 frames from the time you pushed play.  That's 200 ms.  It was amazing.

The figure on the first page of the patent shows the acceleration profile relative to house reference.
  http://www.google.com/patents?id=K043AAAAEBAJ&printsec=abstract&zoom=4#v=onepage&q&f=false

______________________________________________
Please trim posts to relevant info when replying.

Change subject to reflect thread direction. Thanks.
_______________________________________________

Send QuadList list posts to QuadList at quadvideotapegroup.com<mailto:QuadList at quadvideotapegroup.com>
Your subscribe, unsubscribe and digest options are here:
http://mail.quadvideotapegroup.com/mailman/listinfo/quadlist_quadvideotapegroup.com
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://quadvideotapegroup.com/pipermail/quadlist_quadvideotapegroup.com/attachments/20120823/5367c8a4/attachment-0004.html>