[QuadList] Servo Modes

[Norman Hurst]

In the 1970s, my father led an Advanced Development group at RCA Broadcast and one of their projects was to improve the lockup time for VTRs.  Using a TR-70C, they developed a way to achieve lockup within a time measured in frames, not seconds:

  

  http://us.mg4.mail.yahoo.com/neo/launch?.rand=229377417&clmigstart=20110815


It worked by applying an acceleration profile such that when the tape reached the correct speed, it was also in phase with house sync.  I remember that to demonstrate it they had to manually hold the pinch roller against the capstan and keep the electronics in E-E until playback was locked.


The group was in the Terminal Equipment group, not in the VTR group.  When they demoed the system to the VTR group, it got the "NIH" reception: Not Invented Here.  It never made it into any product.



________________________________
 From: Don Norwood <dwnorwood at embarqmail.com>
To: Quad List <quadlist at quadvideotapegroup.com> 
Sent: Tuesday, August 21, 2012 2:38 PM
Subject: Re: [QuadList] Servo Modes
 



 
Hi Chris:
 
I have a VR-1200 that has a mod so that in H-lock mode, it 
functions exactly as you have described for the RCA LineLock.  It's a small 
circuit board added in the control panel.  Basically an NE555 
timer controlling mode selection when Play is activated and the 
servo selector is set for H-lock mode. 
 
Don Norwood
Digitrak Communications, Inc.
www.digitrakcom.com  
 
----- Original Message ----- 
From: Chill315 at aol.com 
> RCA offered four modes of lock, Pixlock, LineLock, Switchlock, and  TW or Tone Wheel.
> 
>Pixlock was the same as Automatic in the Ampex Machines.  Linelock  starts in full automatic and then after lock reverts to the same as  Horizontal, Switchlock was vertical lock, and TW is the original servo  system.
> 
>RCA did have the advantage with LineLock that it would always lock  vertically for a clean switch and then if there was a problem, have a fast  servo recovery.
> 
______________________________________________
Please trim posts to relevant info when replying.

Change subject to reflect thread direction. Thanks.
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