Date: Thu Sep 27 10:44:47 2007

Author: J. Terrence Klopcic

Subject: Re: Welch Cat No 623 e/m Vacuum Tube


Availability of these tubes have been a recurrent theme on TAP-L since I
have been enrolled (2001). As I recall, one message indicated that S-W
periodically gets a new batch made. I don't know if this is true; you might
try contacting the company (although, at S-W, you are not apt to have an
easy time getting in contact with someone who knows either science or
company policy).

Another thread on the theme has been the interest in
finding/hiring/underwriting a glass shop to repair old tubes, perhaps as a
one-time, massive effort. There are, I believe, literally hundreds of
derelict tubes stacked in Physics departments around the country; I have
about a dozen. The maladies are most always: 1) burned out filament or 2)
gas leakage. In 2006, Peter Nelson of K-State wrote the following in a
TAP-L e-mail:


In my efforts to get ours fixed, I have spoken to a company called
Kennetron, who rebuilds all sorts of vaccuum tubes, on several occasions
about repairing ours. They always seem interested in making the repairs
but never reply to my requests for an estimated repair cost. I am
reluctant to risk sending it off to them, at least not while there is a
little life left in the tube. Has anyone else heard of this company, or made contact with them?

- - - - - - - - - - - - - - - - - -
Peter Nelson
K-State Physics
Manhattan, KS 66506


I don't know if Peter ever got anywhere in finding a repair center. There
was also mention of a glass blower at U of Washington who has the expertise
and equipment to set up a repair line.

It is a solvable problem waiting for someone to take ownership: poll the
community to find out how many orders a glass shop could expect, find a
willing glass shop, get it to set a price, and publish the offer. I must
admit that, rather than take on the project myself, I scoured the community
and have amassed a small supply of used tubes, thus relieving Kenyon of the
threat of having to switch to the over-priced, under-sized e/m options.

Good luck.


----- Original Message -----
From: "David Haley"
Sent: Wednesday, September 26, 2007 12:16 PM
Subject: [tap-l] Welch Cat No 623 e/m Vacuum Tube

Does anyone know where to find a replacement for the Welch e/m vacuum tube?
The standard vendors sell replacement tubes but they are for their
particular setup. In the meanwhile, we are looking for a glass blower so we
can repair the 3 broken tubes we have. But it would be wonderful if we
could order it from a vendor instead of a custom job. Has anyone had any
experience with replacing or repairing these tubes? Any help would be
greatly appreciated as we are down to our last tube and it's getting quite
dim. Thank you. Respectfully,

David Haley

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