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

[Videomagnetics]

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 Langdell 
  To: Quad List 
  Sent: Saturday, August 03, 2013 6:11 PM
  Subject: Re: [QuadList] VMI 7811 process (Was AMPEX MARK TEN HIGH-EFFICIENCYVIDEO HEAD...)






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  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 Norwood
      To: Quad List
      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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