[Amps] 3-500Z tube problems

[Carl]

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 at gmail.com>
To: "Jack C. Shutt" <w9gt at frontier.com>; <amps at 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 at 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
>>_______________________________________________
>>Amps mailing list
>>Amps at contesting.com
>>http://lists.contesting.com/mailman/listinfo/amps
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