[Amps] Amp Supply LK500-zc tube asymmetry

[Mike McCarthy, W1NR]

How about a bad drive coupling cap?

Mike, W1NR

Robert Bonner wrote:
> 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.
> 
> BOB DD
> 
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com] On
> Behalf Of Pete Smith
> Sent: Tuesday, March 20, 2007 8:35 AM
> To: Tom W8JI; amps at contesting.com
> 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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