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Re: [Amps] LK500-ZB

To: royanjoy@ncn.net, amps@contesting.com
Subject: Re: [Amps] LK500-ZB
From: TexasRF@aol.com
Date: Wed, 9 Sep 2009 14:54:17 EDT
List-post: <amps@contesting.com">mailto:amps@contesting.com>
Has anyone tried to blow a grid to cathode short with a high current pulse  
of energy? Such as touching the shorted pins for an instant with a car 
battery.  At this point seems not much to loose by trying.
 
73,
Gerald K5GW
 
 
 
 
In a message dated 9/9/2009 1:46:57 P.M. Central Daylight Time,  
royanjoy@ncn.net writes:

About:


"...No visible damage to the case, but now 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...(etc.)"


My ZB had that happen several times when using  Eimac tubes AND before I 
installed a good in-rush protection circuit plus  ridded it of parasitics. 
Never has occured since (with RFP tubes). It's  surely a grid - to - fil 
internal short.

73,   Roy    K6XK



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