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Re: [Amps] 2K Classic X filament issues

Subject: Re: [Amps] 2K Classic X filament issues
From: Jim <>
Date: Wed, 4 Aug 2021 19:28:13 -0500
List-post: <>
I would use a voltmeter and measure the voltage directly on the pins of the tubes.

You can also measure voltage drop of each pin as well.

We are hams. We use test equipment to troubleshoot.


Jim W7RY

On 8/4/2021 7:48 AM, Donald Fox via Amps wrote:
Good morning Pete, et al:

Pete, when you say clips, I assume you mean the small, removeable U shaped 
clips that apply pressure to the socket fingers themselves? The sockets in my 
Henry, are the tried and true Johnson 275s. The main portion of the pins appear 
to be riveted in, so I don't think in can easily move them around. It's 
interesting to note that Henry directly grounded the 3-500 grids, unlike 
Heathkit, Kenwood, etc, who kept the grids slightly above RF ground with small 

As I look at the socket pins, they look clean and what I would call normal. I 
went ahead, and removed/inserted a tube in each socket 3/4 times, and then left 
them in, and fired it up. There appears to be progress, as the brightness of 
both now seems to be almost equal. The ZG tubes with their graphite structure 
are a bit harder to judge, unlike the original Eimac design where the top of 
the star shaped anode assembly is open.

Along this journey, I've discovered that the front 3-500 seems to have about 
60-70% of air flow that the rear one does. I'd sure like to figure that one 
out. Given the size (and noise) of the blower, it's kind of surprising that the 
tubes stay in their sockets, lol.

Henry used those darned Bristol screws to secure the anode coolers to the 
original Eimac's, and I can't seem to locate one to get them swapped over. I'd 
love to get them out of there, and go back in with a normal machine screw for 
ease of service.

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