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Re: [Amps] henry amp problem

To: "'Amps Group'" <>
Subject: Re: [Amps] henry amp problem
From: "David Harmon" <>
Date: Thu, 4 Dec 2014 10:24:38 -0600
List-post: <">>
My Henry 3K Classic X MKll has the same configuration.
I bought it used and it was in pitiful condition far worse than I can
briefly describe here.

One of the several problems was this Henry design error that W1QJ describes.
In my case..........the ceramic feed through had been removed and the
partially melted conductor (allthread) had been put through a ball point pen
plastic body which then was jammed through the chassis hole.
I removed all that crap and then using a chassis punch, enlarged and moved
the hole away from the roller, then re-assembled with copper allthread and
nuts and washers.
After getting it in position and tightened up I soldered the whole thing.
This setup is mechanically stable and there is no ceramic insulator. 
The conductor goes straight through the center of the hole and can't move
I have been using it for 2 years after the repair and it works flawless.


David Harmon
Sperry, OK

-----Original Message-----
From: Amps [] On Behalf Of Zev Darack
Sent: Thursday, December 4, 2014 9:21 AM
To: Douglas Johnson
Cc: Amps Group
Subject: Re: [Amps] henry amp problem

I was looking into a similar problem with 2 other Henry Desktop amps having
no output.  I found this on the web but have not had a chance to review it
yet.  These seem like a pain in the butt to disassemble:

Source: W1QJ
"For the Henry fans out there. There is one common problem with just about
all Henry amps that have the load capacitor below the RF deck chassis.
Henry had a very poor design that eventually failed in amps that were run on
high duty cycle modes like contesting and rtty etc. The defect in the design
is how they brought the connection from the tank coil above the chassis
through to the load cap below the chassis. If you look toward the back of
the roller inductor just below the center line down at chassis level, you
will see a ceramic feed thru. A copper strap will be connected to the top of
the ceramic insulator and on the bottom it connects to the load cap. The
problem is that the ceramic feed thru is not RF rated with a zinc plated
screw or even a SS screw. The screw is very lossy at RF and heats up real
bad. The heat stresses the ceramic and it causes minute cracks. The RF
eventually arcs thru the cracks to ground and the screw beigins to
deteriorate. I have repaired 2 Henry amps already with the symptom of loss
of power for no apprent reason. Now the rub is, if you look at the ceramic
insulator it will look just fine on both sides of the chassis but the center
of it will be burnt out and the screw will almost be eaten through. The
screw is a small #6 screw and it can't handle the power at RF. You have to
remove the insulator and check it. The 2 I fixed both looked good from what
you can see of it but the problem is right in the center where it passes
through the chassis. You can't see that part of it unless you take it apart.
The last one I fixed the #6 screw in the middle was about the diameter of a
toothpick. I did not repair it with a new insulator, I used a piece of
center conductor from RG-8 poly coax and made the connection between the 2
points with that. After the repair both amps had better output. I would
check that insulator if it were my amp for good measure."

On Thu, Dec 4, 2014 at 10:07 AM, Douglas Johnson via Amps <> wrote:

>  During the cw contest my henry 2-kd classic started to act up, no 
> power output on 40-80 meters and after 3 or 4 seconds transmitting on 
> 20 power drops to zero. 10 and are normal output . plate current, 
> plate voltage and grid current remain ok on all the bands and input 
> tuning is normal on all bands. all power goes thru bird wattmeters and 
> bird coax switches which have functioned fine for 35 yrs. I eliminated 
> all of them with 1 coax and wattmeter into the dummy load, same 
> results. At no time did I observe any noise or smell from the amp to 
> indicate trouble, this amp is going to be a pain to remove and open up 
> for repair so I hope to learn something before that has to happen,  
> any comments?....Doug, w9iix 
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