>
>> >// Where is the getter in a 3-500Z?
>> >Where is the getter in an 8877?
>> >Can gettering take place while a tube is cold?
>
>This has been covered a dozen times on this reflector.
>
// I heard about the getter in a 3-500z on AMPS, but I do not recall
seeing any info about a 8877 getter.
>The 3-500 gettering agent is zirconium, the gray powder-looking
>coating on the anode. It is sprayed on, and activates at about 1000
>degrees C. In the ideal case it should run at various temperatures,
>because the gas liberated at one temperature is absorbed at
>another.
>
// 1000º C is yellow/white-hot. If this were the case, gettering would
not take place.
>The 8877 uses tantalum. It is mounted near the cathode and
>heated to temperature by the heater. This was one source of
>chronic 8877 failures in the 80's, because the cathode was moving
>when the tantalum was warping.
>
>All getters outgas to some extent, as do other elements in the
>tube.
>
>Arcs also getter the tubes, by causing a plasma that breaks-down
>the gas into harmless elements that bond to material in the tube.
>As a matter of fact, some tubes are (or used to be) gettered during
>manufacture with intentional internal arcs.
>
>> I recommend contacting the manufacturer for these questions. If you
>> prefer to avoid Eimac, then talk to Claude Peterson at Econco in
>> Woodland, CA. (800) 532 6626. He was involved with some of the glass
>> Eimac tubes at Salt Lake City before they sold that operation. Maybe
>> the 3CX1500A7/8877 as well.... Let us all know what you find out.
>
>Why depend on someone else to accurately convey what is told?
>
// Amen, Mr. Rauch. This why I did not accept the claim that the 3-500Z
was rated at 500mA. This is why I telephoned Eimac about the alleged R&D
Engineering Manager who proved to be as phony as a $3 dollar bill.
http://www.vcnet.com/measures/$3.JPG
>Rather than take second-hand info, you can find books on the
>subject. There are entire chapters on gettering.
>
// Books contain second hand, third hand, and fourth hand info.
>Try the Electronic Designers Handbook and other detailed
>engineering books. Eimac mailed me 19 pages of information in
>1982 titled "Getters and Their Function in Vacuum Tube
>Manufacture".
>
>They also mailed info on neutralizing grounded grid tubes. Rich
>may have copies of both that he hasn't read yet.
// chortle
--- But alas, no answer to the question: Can gettering take place while
a tube is cold?
- My guess is that Mr. Rauch knows that if he grasps this hot potato,
someone is quite likely to quote from Will Angenent's Grate Parasitics
Debate archive.
cheers, Tom Rauch
- R. L. Measures, 805.386.3734, AG6K, www.vcnet.com/measures.
end
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