[Amps] Problem with my Henry 2K-4A

Jim Thomson jim.thom at telus.net
Wed Nov 8 10:46:05 EST 2017

Date: Tue, 7 Nov 2017 21:53:21 -0600
From: Stan Gammons <s_gammons at charter.net>
To: amps at contesting.com
Subject: Re: [Amps] Problem with my Henry 2K-4A

<Every time I've seen negative grid current it was due to a shorted 
<tube.  You might try taking one of the tubes out and seeing if you can 
<isolate it to a single tube.  I don't know what experience you have 
<working on amps, but just be aware there is lethal voltage in the amp.  
<Please exercise caution working on it.



##  Watch out !     The pair of 3-500Z tubes in the 2K-4A  have the heaters wired in SERIES ! 
So no, you cant  run the amp with either tube removed.   Instead of the typ  5V  @  30A  fil xfmr being used,
henry used a 10 V @ 15A fil xfmr.    Dumb idea really. It just means they could use 14 gauge wire instead of 10 gauge wire
for the fil xfmr.   The kenwood  TL-922 uses the same technique. Works, but, when you want to trbl shoot stuff,  and suspect a bad tube 
of the pair, you cant just temp unplug one tube.   On amps where you can unplug one tube, and chimneys are used, you also have to 
temp block the airflow from the socket that has the tube removed. 

##   You most likely have a shorted tube.   In rare cases,  you could also have a leaky bypass capacitor on the cold ends of the fil  choke, 
or a leaky coupling  cap, that feeds DRIVE RF to the socket, or a  coupling cap between heater pins. 

Jim   VE7RF 

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