[QuadList] VR-1200 Capstan Oscillator Mod for Course and FineAdjustment Pots

[Don Norwood]

The mod that Chris describes will certainly work, at the expense of having 625 operation (which was usually not a concern), but there are some other considerations that I'll address in reply to his other post.  Another version of this same approach could also be used for 625 machines that didn't need 525 operation.

Don
  ----- Original Message ----- 
  From: Chill315 at aol.com 
  To: quadlist at quadvideotapegroup.com 
  Sent: Sunday, August 23, 2009 10:59 AM
  Subject: [QuadList] VR-1200 Capstan Oscillator Mod for Course and FineAdjustment Pots


  VR-1200 B Series Inter-Sync 60 Hz Capstan Oscillator Modification


  This was given to me by someone a long time ago.  It made life simpler.

  The capstan Oscillator is difficult to set and is critical for assemble edits.  It sets the free run speed for the capstan.  There is a simple modification that will provide the user with a course and fine adjustment pot for the oscillator.

  Remove Board 13 from the Inter-Sync.

  Find R-78, the 625 Capstan Frequency adjustment.  

  Lift the wire that connects the end of the pot to Q-12 Collector.  This is the end not connected to R-60, a 300K resistor.

  Attach wire disconnected to the End of R-20 that is not connected to R-38, a 20K resistor.

  Reinstall board


  TEST and Setup

  Center R-78

  Adjust Capstan Oscillator using R-20.

  From now on only use R-78 for Capstan Frequency Adjustment unless pot is near the end of range.  Then re-center and set Oscillator with R-20.

  R-20 is now the COURSE adjustment and R-78 is the FINE adjustment.


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