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Re: [Amps] Amp Supply LK500-zc tube asymmetry

To: "'Pete Smith'" <>,"'Tom W8JI'" <>, <>
Subject: Re: [Amps] Amp Supply LK500-zc tube asymmetry
From: "Robert Bonner" <>
Date: Tue, 20 Mar 2007 10:33:57 -0500
List-post: <>
Yes exactly, the problem stays with the rear socket.

Its either the filament pins or other issue at that socket.  Flipping it
over and figuring out which one will find/fix the problem.  My guess is 80%
filament pins on the socket loose, 8% something in the RF path to the
cathode of that tube (as the little fuses in the anode also were blown) 1%
grid coming off ground, 1% evil spirits.


-----Original Message-----
From: [] On
Behalf Of Pete Smith
Sent: Tuesday, March 20, 2007 8:35 AM
To: Tom W8JI;
Subject: Re: [Amps] Amp Supply LK500-zc tube asymmetry

Sure, no argument - though problems in one tube (2 and 4) seem to be pretty 
well ruled out by the fact that it is always the front tube that glows more 
brightly, regardless of which tube is in which socket.

73, Pete N4ZR

  At 09:18 AM 3/20/2007, Tom W8JI wrote:
>>My hypothesis is that resistance between pin and socket electrode at the
>>filament pins was both reducing the amount of filament voltage on that one
>>tube and causing overheating at the tube pin, which eventually melted the
>>solder and also detempered the spring clips.  Because there wasn't enough
>>filament voltage, the tube was taking less than its share of the load.
>He actually could have one of four problems:
>1.) Someone might have floated the grids with glitch resistors (a very bad 
>idea) and one tube could have an open grid path
>2.) One tube might be low on emission either through low filament voltage 
>at the tube or a low emission filament
>3.) Somehow the RF drive or loading could be unequal.
>4.) The tube might have internal problems resulting in more concentrated 
>current than the other tube has, perhaps a broken grid wire. This can hot 
>spot one area of the anode.
>73 Tom

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