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Re: [Amps] Testing Tubes with a Henry 2K

Subject: Re: [Amps] Testing Tubes with a Henry 2K
From: "Mike McCarthy, W1NR" <>
Date: Mon, 23 Aug 2021 07:47:08 -0400
List-post: <>
Yes you can. You need to keep the drive way down and keep grid and plate
currents at half normal IF YOU CAN LOAD IT PROPERLY which is
questionable. I ran mine with one of the 3-400's dead without knowing it
during a contest. I didn't notice until I saw the power out was only
about 500w. As for the loading, maybe running on 20 into a dummy load
with around 40w drive will allow you to tune and load properly.


On 8/22/2021 10:02 PM, Brett Sims wrote:
> Appreciate the responses.  My Henry 2K also has the filaments in parallel.  
> Your right, it was originally designed for 3-400's.   I failed to mention in 
> my original post, it was upgraded to 3-500's with appropriate chimneys and 
> caps.     It works great.
> So if you have a Henry 2k with filaments in parallel and currently runs two 
> 3-500Z's with appropriate chimneys, could one test a single tube?   Wadda ya 
> think?
> Thanks  Brett   N5SQK
> +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Date: Sun, 22 Aug 2021 07:58:30 -0400
> From: "Mike McCarthy, W1NR" < >To: 
> Subject: Re: [Amps] Testing Tubes with a Henry 2K
> Well... My 2K (original) is wired in parallel. It is also designed for 
> 3-400's and won't accept a 3-500 unless you change the chimneys and
> change the heat dissipation caps to low profile ones or lower the sockets...
> Mike, W1NR
> On 8/21/2021 10:40 PM, David Gow wrote:
>>     The Henry 2K series amplifiers have the filaments in series so you must 
>> always have two tubes in the amp..  The manual explains why Henry
>>     made this choice.  You can test a tube by having one known good tube in 
>> the amp as a constant.  After done with the spare tubes put the best in the 
>> amp
>>     instead of the original constant tube.  The measurements will be 
>> relative but at least you have some indication of usefulness.  I love my 
>> 2K--3 but
>>     to test tubes I use my SB-220 which has filaments in parallel
>>     Dave W7VM
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