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

[Wayne Watson]

Yes that is true and if it did not sit "flat" it was called a Zenith error. The AST head was actually split across and lengthwise. Across, and then wired polarity opposite, to correct for the Zenith problem. Lengthwise (a more narrow strip) to provide feedback position; what direction and how much it was bent would give a voltage. With the short "format dropout" in Type C of ten lines there was not much time to get the head to the correct place when it hit the top edge of the tape for the next field and thus the need for feedback info. Ampex was awarded an Emmy for the AST head in 1977; one of two they received that year.


For information on the SAIT Broadcast Systems Technology Program, check out http://broadcast.sait.ca


Wayne Watson
Broadcast Systems Technology
wayne.watson at sait.ca
(403) 284 7079
SAIT Polytechnic
School of ICT
Room G239E
1301 16th Ave. N.W.
Calgary Alberta T2M 0L4
________________________________________
From: quadlist-bounces at quadvideotapegroup.com [quadlist-bounces at quadvideotapegroup.com] On Behalf Of Dennis Degan [DennyD1 at verizon.net]
Sent: Saturday, May 08, 2010 1:54 PM
To: Quad List
Subject: Re: [QuadList] Ampex AST heads and CMC DPT heads--what's different?

                On May 8, 2010, at 11:14 AM, C. Park Seward wrote:

 > I think the Ampex AST head performs the same way. I'll try to find
some docs.

                I offer:

        I somehow remember that the AST head was mounted on TWO strips of
bimorph material sandwiched together.  Flexing of the two would
maintain the head's face flat against the tape.
        A single strip would flex in an arc, which would cause the face of
the head to not be flat against the tape at extreme head position
swings.

                        Dennis Degan, Video Editor-Consultant-Knowledge Bank
                                           NBC Today Show, New York


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