I agree with you with regard to Nuvistors used in a CEI receiver. I had one of the receivers, and several of them were bad. I think the CEI worked them much harder than a typical TV or FM tuner. Finding replacements took a little effort, but the receiver worked well once I replaced them.
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Bruce Gentry, KA2IVY
On 6/18/20 10:02 AM, Jeff Kruth via groups.io wrote:
I have read several times in the thread that Nuvistors do not seem to fail or get weak. This has not been my experience with them.
As one of the largest collectors of WJ & CEI "spook" radios, I have worked on hundreds of pieces of their gear. The original company, Communications Electronics Inc, founded by RE Grimm, used Nuvistors extensively in the products made from the early '60's up into the mid to late 70's. (Along with Mallory Inductuners!, more TV stuff) They used them in the 900 series, the 700 series and the famous RS-111 and its military variant, the URR-52, among others. BTW, NEMS-Clarke & Defense Electronics also used them in their telemetry radios7 IIRC, the types they used were 8058, 7587 and 6CW4, for RF amps, IF amps and LO, respectively. Some 7586's as well. The 8058 & 7587 were prone to getting weak and all reception stopped! I have also found bad 6CW4's but rarely.For a long time 8058 were un-obtanium for me. Many years after I really needed them I got a stash from cleaning out WJ. Such is life. YMMV Jeff Kruth ________________ In a message dated 6/18/2020 12:27:51 AM Eastern Standard Time, email@example.com writes: I read a history of them several months ago, but can not recall where
I found it. The internal structure and envelope were manufactured in
the atmosphere. The rim of the ceramic base was metalized so it would
adhere to brazing. The components were then heated to outgas, then
brazed closed, in a very high vacuum chamber. A getter was not used
because the outgassing process cleaned the components very well. My
experience has been that they are very long lived. The circuitry in
consumer equipment may have also been designed so an aging Nuvistor
would still give good performance, I have never seen any change in
results from replacing a well aged one in a TV or FM receiver, even if
they tested marginally. The low voltage version used in a Tek scope,
however does get weak with time and can have catastropic effect on the
operation of the scope.
Bruce Gentry, KA2IVY
On 6/17/20 10:00 AM, snapdiode via groups.io wrote:
I just think Nuvistors are cool. Any information on how they were made is interesting to me.
I've heard they were made in a high vacuum chamber with the assembly machinery in the vacuum chamber.
There is no exhaust port on a Nuvistor.
I also wonder if there is a getter in there, or if the metal case itself somehow acts as a getter.