[rescue] I want a vacuum tube

Scott Newell newell at cei.net
Wed Oct 29 18:18:23 CDT 2008

At 05:22 PM 10/29/2008, Robert Darlington wrote:
>My buddy's Monarch 10EE lathe uses two big thyratron tubes and several
>others.  Very odd seeing that in there, but the tubes are used to rectify
>the 60Hz AC coming in, then use the thyratrons to create a variable
>frequency AC source for the motor.  The frequency dictates the speed of the
>motor so it's an old "VFD" or variable frequency drive.  Neat stuff and it
>not only works, but it's a production machine in his busy shop.

I'm not so sure...the old ones that I've seen had a DC spindle 
motor.  The tubes were used to adjust the DC voltage (and the field 
voltage) of the spindle motor.

It's a beautiful lathe, BTW.  Never been lucky enough to run one.  (Yet!)

newell  N5TNL 

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