[QuadList] Ampex AST heads and CMC DPT heads--what's different?

[Videomagnetics]

Also let me add to the story. When CMC came out with the DPT. Ampex added a 
piece of metal material in the upper drum  of the VPR-2 scanner that 
prevented the DPT from being installed. CMC did a 180 and had to redesign 
the DPT and when they did this
they took it one step further and made it so it would interchange into any 
of the 1" Ampex VTR's. Ampex at that time had 2 Different AST's one for the 
VPR-2 and 1 that worked in the 3, 6, and 80.  Eventfully Ampex came out with 
a universal AST that worked in all models.  I remember CMC was dumbfounded 
when Ampex did this and it cost them allot to redesign and replace all the 
DPT's that were out in the field...   :) If anyone would like I can post 
pictures of each.


Tony

Videomagnetics Inc
----- Original Message ----- 
From: "Tim Stoffel" <tim at lionlamb.us>
To: "Quad List" <quadlist at quadvideotapegroup.com>
Sent: Saturday, May 08, 2010 2:00 AM
Subject: Re: [QuadList] Ampex AST heads and CMC DPT heads--what's different?


> On Fri, 2010-05-07 at 20:56 -0700, Ted Langdell wrote:
>> Yes... AST was an Ampex trademark, and DPT "Dynamic Parallell
>> Tracking" was apparently a TM of CMC.
>>
>>
>> I'm just curious to know what's different... and the story behind it.
>>
>>
>> Ted
>>
>   An AST head has a single, planar bimorph crystal with the head tip
> glued to the end of it. When the head tip moves up and down with the
> bimorph, it describe a (small arc), with the angle of the head tip
> contacting the tape changing as the head moves.
>   CMC determined that the aforementioned angle change hurt the
> performance of the head. So, they added a cantilever to the bimorph
> crystal that actually carries the head tip. Now, when the bimorph moves
> up or down, the cantilever adjusts in such a way as to keep the head tip
> perpendicular to the tape.
>    In general, AST and DPT heads are interchangeable. However, some
> machines required that some pots in the AST servo be preset to a certain
> value before changing head types, to get the servo 'close enough' to be
> stable for alignment.
>
> Tim Stoffel
>
>
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