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Re: [Amps] LK500-ZB

To: amps@contesting.com
Subject: Re: [Amps] LK500-ZB
From: Paul Decker <kg7hf@comcast.net>
Date: Fri, 11 Sep 2009 13:09:33 +0000 (UTC)
List-post: <amps@contesting.com">mailto:amps@contesting.com>

Thanks to all that replied.   At this point, I think a tube has gone bad.  
Removing the "bright" tube, the amp can be loaded up and produces output.   
Swapping the sockets, the problem seems to follow the tube.   



As was pointed out, I don't have anything to loose with the bad tube.   There 
was some talk about "blowing the short out".   I don't have a 400VDC supply, 
but I guess I could rectify a 240 VAC line, that would get me about 380 VDC @ 
15 amps.    Another suggested a car battery.   I do have an adjustable 60 vdc @ 
60 A current limiting supply available.   Would I just put this to the heater 
pins? 



thanks, 

Paul (KG7HF) 







...when the amp is turned on, but in standby, the plate current reads about 
200mA and the grid current is pegged negative.  Plate voltage is lower than 
what it used to be, about 2600 V.   Switching between RX/TX doesn't seem to 
have any affect, I can hear the relay kick.   One final observation, in RX, one 
tube starts to glow orange, while the other stays the normal light yellow 
color.  



It seems as if maybe somehow the tube is internally shorted or something.   
Ideas, suggestions.. 






 
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