[QuadList] What is it????

[Bill]

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 <http://www.digitrakcom.com>
>
>     ----- Original Message -----
>     *From:* Chill315 at aol.com <mailto:Chill315 at aol.com>
>     *To:* quadlist at quadvideotapegroup.com
>     <mailto: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
>
>
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