[QuadList] VMI 7811 process (Was AMPEX MARK TENHIGH-EFFICIENCYVIDEO HEAD...)

[David Dean]

Hi 

 

Can you give any more information about the "Solid State" Transformer, a few
pictures might help.

 

Thanks

 

David Dean

Westpoint Television

Now with Snell Shakeout

0208 742 3400

 

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From: QuadList [mailto:quadlist-bounces at quadvideotapegroup.com] On Behalf Of
Videomagnetics
Sent: 05 August 2013 18:16
To: Quad List
Subject: Re: [QuadList] VMI 7811 process (Was AMPEX MARK
TENHIGH-EFFICIENCYVIDEO HEAD...)

 

Process 7811

Ted Barger who was the founder of Videomax and Videomagnetics had a company
back east called Forgflo who supported RCA and developed the transformer for
the high band heads. This transformer was a solid state rotor/stator
configuration with only one moving part. The inductance is set by the gap
between the space of the rotor and stator and would never change. This was
far superior to the Ampex transformer which has two ferrite rotating cores
for each transducer. The inductance is set by a thrust screw and ball
bearing. This screw and bearing start to wear out when the head is spinning
and as this happens the inductance will change and the ferrite cores start
to rub against each other, become hot and causes damage to the cores. It is
a long tedious process to rebuild the Ampex transformer. All the cores are
wound by hand and require matched sets for thickness and stacked precisely
for the proper gap. We charged about $200.00 for converting the Ampex
transformer to the solid state. When ever Ampex or CMC would get one of our
converted heads in for refurbish they were not happy and would call us to
see if we wanted to exchange them. At one point I believe at least CMC would
charge their customer extra to swap out the transformer. So as history goes.
----- 

 

 

 

iginal Message ----- 

From: Ted <mailto:ted at quadvideotapegroup.com>  Langdell 

To: Quad List <mailto:quadlist at quadvideotapegroup.com>  

Sent: Saturday, August 03, 2013 6:11 PM

Subject: Re: [QuadList] VMI 7811 process (Was AMPEX MARK TEN
HIGH-EFFICIENCYVIDEO HEAD...)

 

 


  _____  


Tony, 

 

Cool that you can pull up that information!

 

Can you tell us more about the 7811 process... what that involved and why
that was done?

 

I remember you telling me about why you liked the way RCA did their head
design and manufacture.  The list would probably like to hear about that.

 

Ted

 




Ted Langdell

Secretary

Skype:  TedLangdell

e-mail: ted at quadvideotapegroup.com

 

 

 

On Aug 3, 2013, at 4:28 PM, Videomagnetics wrote:





I just checked our log book and we refurbished this head back in 1982....
Looks good as new... the 7811 process was an RCA type transformer
conversion.

 

Tony

----- Original Message -----

From: Don <mailto:dwnorwood at embarqmail.com>  Norwood

To: Quad List <mailto:quadlist at quadvideotapegroup.com> 

Sent: Saturday, August 03, 2013 3:31 PM

Subject: Re: [QuadList] AMPEX MARK TEN HIGH-EFFICIENCY VIDEO HEAD IN CASE

 

 

 


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Hi Chris.....

 

You'll note that all of the parts this seller is offering are likely from a
VR-1000.  The reel motor is definitely VR-1000, the capstan motor likely is
(note the caps which are not used on Intersync systems), and the head is
ball bearing.  Can't tell from the pics what module is installed, but most
likely trim pot.  The head could also be used on a VR-1100 that hasn't been
updated, but isn't useful for a 1200 or 2000.  The capstan can be used by
removing the caps, but the point is it's likely quite old, and the belt
could also be a problem.  Just thoughts for anyone looking at these for
spares!

 

Don

 

 



 



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