Bad Ion Gauge Tube?

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David Kunkle
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Bad Ion Gauge Tube?

Post by David Kunkle »

Had a problem with my first ion gauge tube, so I got this used tube off ebay:

http://www.ebay.com/itm/ETI-Electron-Te ... true&rt=nc

When I turn on my Varian 845, one filament in the tube lights for a second and then the Varian shuts itself off. Never a reading on the digital display- does the same thing when no tube is connected and I turn on the Varian.

The new tube has a row of 4 pins, then one pin on either side of that row- total of 6. My old tube has 4 in a row and one pin on one side- 5 pins total. And the cable has a 6 pin arrangement that fits either tube, but it is obvious that the one side pin hole has no metal connector down in it. (cable bought new from Duniway) The filament in the new tube only lights for a second if the cable's connector is rotated 1 way only out of the 2 possible ways. Something wrong with the new tube or not the proper cable? I thought any ion gauge tube should work with my gauge and cable. Thanks.

And now that I look at more on ebay, some only have the 4 pins in a row total. What gives?
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
Roberto Ferrari
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Re: Bad Ion Gauge Tube?

Post by Roberto Ferrari »

Hi David

Hard to tell without a diagram but most controllers shut off the filament power when vacuum level is too bad.
Are you pumping down your system?
David Kunkle
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Re: Bad Ion Gauge Tube?

Post by David Kunkle »

My Varian will shut down the tube at 100 microns. Everything worked fine with that first tube I had. My TC tells me I'm down to 5 to 10 microns. No problems until I switched to this new tube.
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
Roberto Ferrari
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Re: Bad Ion Gauge Tube?

Post by Roberto Ferrari »

No short filament/grid?
David Kunkle
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Re: Bad Ion Gauge Tube?

Post by David Kunkle »

Since you mentioned that, I took a close look inside with a flashlight (kinda hard since it's a coated tube). There is another filament on the opposite side from the one that momentarily glows. That filament is broken near the middle- not touching anything far as I can tell- but broken. It's what I thought- a bad tube- just couldn't put my finger on the why.

Ebay guy already agreed to take it back earlier this afternoon. At least now I can tell him why it's bad. On the other hand, now I have to go find another tube and wait for it. :(
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
Roberto Ferrari
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Re: Bad Ion Gauge Tube?

Post by Roberto Ferrari »

Well, good enough he accepted to refund you!
David Kunkle
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Re: Bad Ion Gauge Tube?

Post by David Kunkle »

No fight there at least. Probably went bad when a real scientist was using it, and he threw it in a corner to collect dust (in case he might need it someday). Winds up in a box many years later that gets auctioned off for pennies. Someone like me without a $1M government grant buys it off ebay. Heavy sigh. Them's the breaks.
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
Bruce Meagher
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Re: Bad Ion Gauge Tube?

Post by Bruce Meagher »

That appears to be a dual tungsten filament BA gauge, and from your description above one of the filaments is blown. My 845 has a filament selector on the back, and if one of the filaments lights there's hope. Are you sure you selected the correct gauge type? I believe it's a 563 type gauge. The diagram on page 16 of the manual shows how to select that type. Also check the pinout of your cable and compare to the diagram on page 11 to ensure it matches.

Bruce
David Kunkle
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Re: Bad Ion Gauge Tube?

Post by David Kunkle »

If the Varian is switched to filament #2, it does nothing no matter how everything's connected. The jumper is already set to 563- same as the last tube required.
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
ian_krase
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Re: Bad Ion Gauge Tube?

Post by ian_krase »

or maybe you flip the tube connector around? That's how mine works.
David Kunkle
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Re: Bad Ion Gauge Tube?

Post by David Kunkle »

It had been a few years since I put my gauge system together. Meaning I forgot the tube and cable types have to be compatible. I realize now my cable is for a single filament. The tube had 1 broken filament, and I recently realized it was contaminated with a thin film of something that wouldn't wash out with acetone. I dug up an article that said these tubes can be cleaned with only acetone, and if that didn't work, the filament and the whole tube would be trash. At that rate, I'm figuring it'll be easier to start over with the right type of tube.
If your experiment needs statistics, you ought to have done a better experiment.

Ernest Rutherford
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