<html><body><div style="color:#000; background-color:#fff; font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:24px"><div><span>Back in the days before I knew anything about Quad (1968) the VR-7800 had the only useable Assemble mode. <br></span></div><div style="color: rgb(0, 0, 0); font-size: 24px; font-family: HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif; background-color: transparent; font-style: normal;"><span>The practice of recording black and using only insert edits, was based on the fact that all of the Quads switched from control track playback to a reference oscillator at the point of the assemble edit. The VR-3000 always made good assemble, backspace edits.</span></div><div style="color: rgb(0, 0, 0); font-size: 24px; font-family: HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif; background-color: transparent; font-style: normal;"><span>The VR-7800
(pre-A, 1" helical scan) had a multi-tooth capstan tach (16) and a circuit to select the closest tach tooth to control track and use that as the reference for the record portion of an assemble edit, thus eliminating the assemble edit problem. I think this was Barry Guislinger's great idea!</span></div><div style="color: rgb(0, 0, 0); font-size: 24px; font-family: HelveticaNeue,Helvetica Neue,Helvetica,Arial,Lucida Grande,sans-serif; background-color: transparent; font-style: normal;"><span>When I explained this to good quad engineers, they were both pleased and suprised!<br></span></div><div> </div><div>Bye for now, love to all, Bill & Gewyn & Ginger (whoof...whoof)</div><div><br></div> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 24px;"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 12pt;"> <div dir="ltr">
<hr size="1"> <font size="2" face="Arial"> <b><span style="font-weight:bold;">From:</span></b> Don Norwood via QuadList <quadlist@quadvideotapegroup.com><br> <b><span style="font-weight: bold;">To:</span></b> Quad List <quadlist@quadvideotapegroup.com> <br> <b><span style="font-weight: bold;">Sent:</span></b> Wednesday, December 31, 1969 4:00 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [QuadList] Capstan questions<br> </font> </div> <div class="y_msg_container"><br><div class="qtdSeparateBR"><br><br></div><div class="yqt6759503900" id="yqtfd98474"><br clear="none"></div>In reply to the original question that Chris asked, I think I have a drawing <br clear="none">that shows the tolerance for the Ampex VR series capstan. I'll look for it. <br clear="none">RCA used a smaller diameter capstan, so tolerances might be different in <br clear="none">their case.<br clear="none"><br clear="none">I think everybody
understands that the goal in record mode is to move the <br clear="none">tape at a constant and precise rate. However, that doesn't happen in real <br clear="none">life with the VR series as evidenced by the experiment that Chris did. I've <br clear="none">seen the same thing. I'm not sure about the capstan tolerance issue, but I <br clear="none">do know that tape slippage can affect the speed. This can be caused by <br clear="none">incorrect tape tensions, bad pinch rollers, slick capstans, or some <br clear="none">combination of all of the above. Further, the tape itself can slip <br clear="none">differently depending on the backing.<br clear="none"><br clear="none">Also, in the VR decks, remember that the capstan is not directly driven. So <br clear="none">the complete system includes the motor pulley, the mylar belt and the <br clear="none">capstan pulley. Remember that you have to properly set the tension
on the <br clear="none">belt.<br clear="none"><br clear="none">More precise control of record speed can be achieved by using a high <br clear="none">resolution tach that measures the tape motion, not the capstan speed. That <br clear="none">technology wasn't practical in early quad machines, and as others have <br clear="none">pointed out, within practical limits, the error is corrected in playback <br clear="none">anyway.<br clear="none"><br clear="none">Don Norwood<br clear="none">Digitrak Communications, Inc.<br clear="none">www.digitrakcom.com <div class="yqt6759503900" id="yqtfd08941"><br clear="none"><br clear="none"><br clear="none"><br clear="none"></div><br><div class="yqt6759503900" id="yqtfd60654">______________________________________________<br clear="none">Please trim posts to relevant info when replying.<br clear="none"><br clear="none">Change subject to reflect thread direction. Thanks.<br
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