Varian 524 Clod Cathode Gauge?

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Varian 524 Clod Cathode Gauge?

Post by AllenWallace » Thu Aug 19, 2010 3:28 am

I recently pulled a Varian 524-2 cold cathode gauge and controller from an old scanning electron microscope. A bit of web research suggests that the Varian 524 and 525 are similar. One PDF document suggests that you drive the tube with 2 KV and that the sensitivity is 2 amperes per Torr, from E-2 to E-6 torr.

My controller was integrated into other electronics, so I cannot simply extract what I need to create a stand alone controller. The electronic package has a meter on the front panel and a red potted assembly mounted on a PCB.

Has anybody had any experience with the Varian 524 and /or this red potted power supply thingy? I'll attempt to reverse engineer the schematic of the supporting electronics, but I'm hoping some can give me a head start.
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Richard Hull
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Re: Varian 524 Clod Cathode Gauge?

Post by Richard Hull » Thu Aug 19, 2010 3:09 pm

Cold cathode gauges tend to be non-linear. Therefore, you should keep any supply and or readout and electronics that appeared with the gauge in the original gear. I assume you have all this at hand? If the supply "thingy" has a lead going to the gauge, then you need to figure its connections out or retain the bulk of the instrument in some fashion. These things use between 1.5 and 3KV. I think mine used about 2.4kv

A cold cathode gauge is excellent for fusor work when used in conjunction with a standard TC gauge. The combo usually offers a cheap solution to fusor vacuum work if you can't secure an adequate capacitance gauge.

I was prepared to use an old varian CC gauge with vacuum tube based metering circuit on my fusor IV, but came into posssion of a .1 torr capacitive manometer gauge which is far more accurate and not gas type sensitive. I did use the CC gauge for about two weeks and liked it a lot. I picked up the old varian CC gauge and the electronics for about $25.00 at a hamfest. I retain it now as a fall back should the capacitance gauge go south on me.

Some of this older intergrated stuff like you seem to have just needs to be noodled out on a case by case basis and requires a bit of fore knowledge of how the gauges work and a bit of electronics background.

For scrounging purposes, one needs to not only know a bit of engineering, but also a bit about how to reverse engineer.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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