[QuadList] Blanking Issues

[Trevor Brown]

I think you need to separate politics from engineering

 

C format came from a committee on which Ampex and Sony both had seats 

Ampex were already up and running with a very nice helical and so had a
market lead

 

Sony insisted sync heads to record the missing part of the picture

 

Once these heads became spec even if you did not want to record blank lines,
you had to fit dummy heads to maintain interchange

 

Sony always insisted it was for non TBC machines so you could fill the
missing band with tape info

 

The fact that it was recorded at the other side of the drum where the
tension is different and so could not be used with processing seemed to be
overlooked

 

And Ampex had to redesign the scanner and loose there market lead

 

Apologies to any Sony people, but dummy heads or sync head was politics not
engineering

 

Trevor

UK member

 

From: quadlist-bounces at quadvideotapegroup.com
[mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of Scott Thomas
Sent: 07 February 2010 06:59
To: Quad List
Subject: [QuadList] Blanking Issues

 

Talking about Type-C for a moment; I can't remember if it was Sony or Ampex
(or both?), but they had a separate "sync" head on the scanner. I'm assuming
that was to have a clean sync pulse on the head switch? A problem obviated
by a TBC?

 

Scott Thomas

 

On Feb 6, 2010, at 5:20 PM, Don Norwood wrote:





Hi Park:

 

All of the Type-A 1" machines up thru the VR-7800 had the switch above the
vertical interval.  The VPR-7900 was the first to place it in the vertical.
Remember also that the Type-A machines are single head, so there is more
than a "switch", there is a dropout for several lines.  The VR-660 is a
2-head design so there is a switch and no dropout.

 

When Sony made their first 1/2" machines, there was apparently some "reverse
engineering" done on their Ampex predecessors.  Although the Sony machines
were 2-head, they had a "blanking" circuit that covered up the switching
point and produced a totally blank area in the same location as the Ampex
Type-A.  There was no logical reason for that other than replicating the
output signal of the Ampex.  The practice was discontinued in subsequent
models.

 

Don Norwood
www.digitrakcom.com  

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