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Re: [Amps] GI-7b issues

To: "Robert Perdue" <>
Subject: Re: [Amps] GI-7b issues
From: "k7rdx" <>
Date: Tue, 9 Sep 2008 13:02:44 -0700
List-post: <">>
Best solution would be to convert to a liquid cooling system or build 
coolers similar to GS-35b style copper radiator. The 7b coolers have casting 
air pocket flaws and the taper doesn`t always match the flange on the 
tube..With the large number of conversions being done by hams,someone needs 
to design & market a decent cooler..Jim..K7RDX..
----- Original Message ----- 
From: "Larry" <>
To: "Robert Perdue" <>
Cc: <>
Sent: Tuesday, September 09, 2008 12:24 PM
Subject: Re: [Amps] GI-7b issues

> The cooling in those conversions is nowhere near enough.
> The GI-7B anode cooler is not very efficient. It cannot be properly
> cooled with a fan blowing at it. In order to realize any decent
> reliability you MUST use a pressurized chassis with proper air flow
> around the base and through the cooler and the blower MUST be a 3 inch
> or larger squirrel cage turning at 3000 RPM or more.
> I've done extensive testing of the GI-7B in a static test setup and
> compared seal temperature against actual anode dissipation and air flow.
>  I did this after having some of the same problems in my 432 amp that
> you have experienced. See the 432 GI-7B amp on my web page. The result
> of the testing was a rebuild of the air system so that the tubes didn't
> run away and self destruct.
> Good luck.
> Larry - W7IUV
> DN07dg
> Robert Perdue wrote:
>> Looking for any info on the GLA-1000 conversion to the GI-7b tube. I have 
>> done the w4emf conversion but I am having problems with the tubes self 
>> destructing. has anyone else had issues with this tube? The amp runs fine 
>> and then boom the tube melts down without any indications I have watched 
>> current draw very close and that seemed fine but the tube just fails with 
>> a pop it melts the solder out of the tube around the Anode cap. Could it 
>> go into oscillation causing this? And for some background I ran the 
>> filaments for 48 hours before use. I have got 4 more tubes ready to go 
>> again but would like to find the problem before proceeding. Anyone else 
>> having failures?
>> 73, Bob kc0hfl
>> _______________________________________________
>> Amps mailing list
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