[Amps] April QST article on RF power tube test stand

[Charlie Young]

I have used my AL-1500 and AL-82 many times to test 8877 and 3-500 tubes of unknown condition. 
 
With the primary connections on the plate transformer being push on spade lugs, it is simple to unplug it leaving  the filament and control voltages as normal in the amp.  I use a 120VAC variac applied to one of the HV primary windings, and bring the HV up slow on the tube to be tested.  I also insert a fast blow low current fuse between the HV and tube anode, just as a precaution.  
 
The spade lug plate transformer connections make this very fast and easy to setup for a tube test.   
 
After the tube holds full HV without arcing and draws normal idle current when keyed, I test it with low RF drive levels.  If that is OK I hook the transformer primary back up to full voltage and do a full output test.  
 
73 Charlie N8RR 
 
 

> Date: Sun, 18 Mar 2012 09:13:50 -0500
> From: ranchorobbo at gmail.com
> To: amps at contesting.com
> Subject: [Amps] April QST article on RF power tube test stand
> 
> Has anyone read the article in QST on building a test setup for RF
> power tubes (3-500 and 8877 in the article) for gettering tubes of
> unknown status?
> 
> Seems to me like a lot of work when, if you have an amp that uses a
> tube you want to check out, you can just put a variac in the line to
> the plate transformer primary and pretty much have what they built
> from scratch.
> 
> 
> 
> 73
> 
> Rob
> K5UJ
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