<html><head><style type='text/css'>p { margin: 0; }</style></head><body><div style='font-family: verdana,helvetica,sans-serif; font-size: 12pt; color: #000000'><P>Hello Don,</P>
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<P>Attached is a manual page from a RCA TR-60 describing the vacuum arrangement.</P>
<P>When the machine is in standby or winding the gauge reads 100 in/h2o and when in play or rec modes it drops to 35in.(Ibelieve I said 40, but it is actually 35in.)</P>
<P>I dont know when RCA instituted this vacuum switching arrangement or how many models it was on, but it is on the 60 here, and it was on a 61 at work years ago. </P>
<P>I will look around thru some more RCA manuals here. You have gotten my curiousity up a little now as well.</P>
<P> </P>
<P>Larry</P>
<P> </P>
<P>LE Odham</P>
<P>Engr/Tech</P>
<P>TAMIS Archive</P>
<P>Knoxville,Tenn.<BR><BR></P>
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<DIV>Hi Larry:</DIV>
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<DIV>Perhaps some clarification is needed regarding what pressure is where. I have no problem adjusting the supply regulator for the venturi to produce the required 40 inches of water vacuum when using the standard 55 psi supply. However, my air distribution system outside of the machine is higher pressure. </DIV>
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<DIV>My approach, whether for a single machine or multiple machines, is to have the compressor (with tank, filters, etc. sized accordingly) supplying high pressure to the machine(s) location and have a regulator installed on the input to each machine which adjusts and regulates the pressure to 55 psi where it enters the machine. So the path is: hi-pressure into the regulator, then 55 psi out split to: 1) venturi supply regulator, and 2) a check valve. The venturi supply regulator reduces the 55 psi to whatever pressure is required to generate the 40 inches of vacuum. Meanwhile, on the other side of the 55 psi split, the output of the check valve goes to the pressure interlock switches, the internal reservoir tank and the head bearing.</DIV>
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<DIV>Very interesting what you said about the RCA machines increasing the guide vacuum during wind. I didn't know that. Most of my RCA experience was TRT-1B and a little TR-22. After that, almost all Ampex except for a few minor encounters.</DIV>
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<DIV>Don Norwood<BR>Digitrak Communications, Inc.<BR><A href="http://www.digitrakcom.com/" target=_blank>www.digitrakcom.com</A></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B> <A title=leodham@centurylink.net href="mailto:leodham@centurylink.net" target=_blank>L.E. Odham</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=quadlist@quadvideotapegroup.com href="mailto:quadlist@quadvideotapegroup.com" target=_blank>Quad List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, June 02, 2012 10:34 AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [QuadList] Ampex Quad VTR Airflow Requirements</DIV>
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<P>Ditto.</P>
<P>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.</P>
<P>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.</P>
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<P>my 2 cents,</P>
<P>larry</P>
<P> </P>
<P>LE Odham</P>
<P>Engr/Tech</P>
<P>TAMIS Archive</P>
<P>Knoxville, Tenn.<BR><BR></P>
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