[QuadList] What is it????

Sun May 15 12:02:25 CDT 2011

Hi Bill Herzog & Folks,

I am very pleased to hear about the engineering side of the great TBC design efforts that were going on upstairs @ building #3. All this while I was making the move from Helical to Quad. And of course the changes in the Nova project with the project engineer, Charlie Crum leaving to start the Catholic Broadcast Network, a couple of weeks after I moved over to the Broadcast Side of Product Management. 
Keep up the great work, olde friend, and please give us all more of your engineering insight.

Bye for now, Bill & Gewyn & Ginger (whoof...whoof)

--- On Sat, 5/14/11, Bill <bherzog at budget.net> wrote:

From: Bill <bherzog at budget.net>
Subject: Re: [QuadList] What is it????
To: "Quad List" <quadlist at quadvideotapegroup.com>
Date: Saturday, May 14, 2011, 11:20 PM

  After the AVR1 was production released there were a lot
        of
        Redwood City engineers sitting around with very little to do.  There were no active development budgets
        other than MPD (maintenance of product design), and the camera
        projects.  I was bootlegging the design
        of a NTSC
        encoder based on Charley Coleman’s Pal encoder prototype he
        designed for the
        Universal Colortec project.  Somehow I
        came up with what I thought was an original error detector
        circuit.  Instead of comparing sync
        versus a reference
        and generating an error voltage that controlled a variable delay
        line, this
        circuit simply looked at the first sync pulse that came along
        after the
        reference from a series of taps on a long delay line.  Whichever tap first produced a sync after
        the reference, that was
        the tap that should be used and was selected as the output.  The video then went into the vernier
        corrector exactly as the AVR1.  The
        vernier corrector was essentially a modern version of Colortec.  I built a breadboard to prove the logic and
        demonstrated it to Charles Anderson the manager. 
        He liked it and said they had been thinking about a new
        model
        Quad machine with a box that replaced Amtec, Colortec, Velocity
        Comp, and
        Processor.  Within a month I had a
        budget, and the Minibuffer was started with a staff of about 4
        men including
        myself.  We were proceeding quite
        rapidly, because a lot of the boards were just lifts from the
        AVR1, when
        Charles Anderson said to start thinking how to make it helical
        as well as
        quad.  Apparently there was a need for a
        helical tbc, and this might fit the bill. 
        In the end the tbc ended up helical only, but there were
        months there
        that it was to be a dual purpose tbc. 
        There was a significant cost reduction in the delay lines
        opposed to those
        in the AVR1, because the delay lines were conventional lumped
        constant delays passing
        baseband video.  This was much less
        expensive than the rf based mod/demod glass lines used in the
        AVR1.  I put the rf connectors on the
        front panel,
        because I didn’t like having to make precise alignment fixtures
        so the boards
        would plug into the back, as the AVR1. 
        I don’t remember the connector pins being reversed, and
        have no
        explanation how that happened.  The
        entire project for the 790 tbc was rather inexpensive as
        projects went in those
        days, and we had no major delays.  Simultaneously
Maurice
        Lemoine was championing a digital tbc, but was delayed funding
        for
        considerable time.  There were still a
        lot of questions about the “quality” of digital. 
        Number of bits, sampling frequency, multigeneration, etc.  Maurice had to bootleg his A to D for quite
        a while before he actually got funded. 
        I don’t know for sure, but I always assumed that the
        powers that be
        considered my approach to another tbc the safer route at that
        time.  
    Bill Herzog

    On 5/14/2011 9:07 AM, Don Norwood wrote:

      Hi Chris:

      I'll agree that the IVC interchange was
          better.  Beyond that, both the electronics and the transports
          had issues.  While the transport looked very "professional", a
          check underneath revealed some serious shortcomings,
          especially the lack of direct drive servo system for the
          drum.  As the machines aged, this became even more apparent
          when the pulley wore to the point that the head could never
          achieve speed!

      As for the TBC designs, the analog TBC-790
          came out in '72.  At that point, I'd guess that the cost of
          digital was still too high for the helical market.  Two years
          later in '74, the TBC-800 was introduced as Ampex's first DTBC
          for helical.  Weighing in at a mere 100 lbs compared to the
          120 lbs of the 790, it had a 1-H correction window and list
          price was $11,500 plus an additional $3,500 for Velcomp.  The
          790 had been priced at $10,000 for the base unit and only had
          a correction window of +/-1.5 usec, so for about the same
          price, there was a huge performance increase in two years. 
          Then, in another two years ('76), the TBC-1 at $12,800 plus
          only $1,500 for Velcomp offered a +/-6H window for less cost
          than the TBC-800.  It was also down to a lightweight 80 lbs!

      Don Norwood

          Digitrak Communications, Inc.

          www.digitrakcom.com

        ----- Original Message ----- 
        From: Chill315 at aol.com 
        To: quadlist at quadvideotapegroup.com

        Sent: Saturday, May 14,
          2011 7:02 AM
        Subject: Re: [QuadList]
          What is it????

          Bill

          Very interesting history.  I have used a few different
            models of the EIPD machines.  7000, 7500, 5000 series and a
            7800.  They were decent but had issues.  When IVC came
            along, a number of us wished that one could combine the
            Ampex electronics with the IVC transport because it held
            interchange a whole lot better.  Actually we were
            complaining about the swing arms in the EIPD machines.  

          The TBC designed for the 7900 was interesting.  I still
            wonder why that path was chosen for the design.  Was it
            because it was so early in the digital age that the cost was
            too high to produce a TBC?   Was it too early for the
            engineering skills?  Was there a time issue to get the
            product for market?  Or was the culture at Ampex such that
            it had lost its way.

          I remember being told about the letter for the
            discontinuance of InstaVision.  It said something like "Due
            to the unprecedented success of Instavision, we are
            discontinuing the product."  A fellow by the name of Doug
            Mumley was working for EIPD here in Detroit and saved the
            letter.

          Chris Hill
          WA8IGN

_______________________________________________
Please trim posts to relevant info when replying!
Send QuadList list posts to QuadList at quadvideotapegroup.com
Your subscribe, unsubscribe and digest options are here:
http://mail.quadvideotapegroup.com/mailman/listinfo/quadlist_quadvideotapegroup.com

-----Inline Attachment Follows-----

_______________________________________________
Please trim posts to relevant info when replying!
Send QuadList list posts to 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/20110515/df6c0d40/attachment-0004.html>