[QuadList] Ampex Quad VTR Airflow Requirements

[L.E. Odham]

Ditto. 

I seem to recall that when we updated the Ampexes at the station I worked at, we had to run the air supply up to 80 psi in order to get the venturis to reliably produce 70 in., and then adjust it down to 40 in. vacuum with a norgren regulator valve. That gave some reserve vacuum supply for adjustment,variation,etc. 

Also on the RCA machines, it had to be 80 psi because there was a valve soleniod that engaged during rewind placing 100 in. vacuum on the guide. 



my 2 cents, 

larry 



LE Odham 

Engr/Tech 

TAMIS Archive 

Knoxville, Tenn. 



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

Roger, 
  
Some excellent info from Park in the Ampex FEB's.  However, a very important caveat.....those papers do NOT reflect the load of a machine with a venturi vacuum system.  They are for the standard machines with a vacuum pump.  Ampex didn't use the venturi vacuum on any of the VR-xxxx models although many were updated with the Merlin mod kit. 
  
So, be aware that a venturi equipped machine requires about twice the volume of air, almost 1 cfm as I stated in my earlier reply.  Actually, it's typically a bit over 0.9 cfm, so rounding gets you to 1 cfm.  There are a number of compressor options that will deliver what you need, and there is a used market because of their applications in industrial, medical and instrumentation, so you can often find a compressor for much less than new cost if you are willing to wait for the right unit to come along.  
  
There are also some variances in the prescribed head operating pressures.  I'd be interested to know what the folks that are rebuilding heads specify today.  I've always gone by the settings that I listed earlier from the Ampex manual, but perhaps slightly higher is OK.  Certainly better than too low I would think! 
  
Don Norwood 
Digitrak Communications, Inc. 
www.digitrakcom.com 
Please trim posts to relevant info when replying. 

Change subject to reflect thread direction. Thanks. 
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