The weld problem was due to a cheapened down assembly where the original
anode to top assembly was fully welded to just 3 spot welds. This was at the
SLC plant which was known for several other dumb moves.
I have one of those leaning top tubes here on display.
Carl
KM1H
----- Original Message -----
From: "Vic Rosenthal" <k2vco.vic@gmail.com>
To: "Jack C. Shutt" <w9gt@frontier.com>; <amps@contesting.com>
Sent: Monday, June 13, 2016 9:39 AM
Subject: Re: [Amps] 3-500Z tube problems
I have seen a few of these in genuine Eimacs from a specific period. I
don't recall the date codes, but I'm sure someone here knows. The problem
was bad welds which allowed the grid assembly to move and touch the
filament.
In the cases that I had, the short only appeared when the filament was
hot. I doubt that this could be cleared by an electrical procedure, but
maybe a slap on the tube in the right place would work, at least
temporarily.
--
Vic 4X6GP
On June 11, 2016 7:55:55 PM GMT+03:00, "Jack C. Shutt"
<w9gt@frontier.com> wrote:
Hello all. I don't post here very often, but always enjoy reading the
posts and comments about the experiences of others.I'm looking for some
info and advice on 3-500Z tubes. I have used these tubes for many
years in several home brew amps, as well as in a few commercially-built
units. I recently have had some bad experiences with bad tubes (fil to
grid shorts?) resulting in the loss of some expensive components such
as the fil/bias transformer, grid meter, and bias circuitry consisting
of hard-to-find high power zener diodes, etc. I'm wondering if anyone
has had any success in reviving bad tubes with shorts. Is there a
procedure that can be used for clearing these shorts? Also wondering
about design additions that you may have included in amps to protect
the circuitry from catastrophic failures. I have experienced failures
of Eimac tubes and Chinese versions. Looking forward to your comments.
73, Jack, W9GT
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