[Top] [All Lists]

Re: [Amps] GI-7b issues

To: "Larry" <>
Subject: Re: [Amps] GI-7b issues
From: "Carl" <>
Date: Tue, 9 Sep 2008 17:41:43 -0400
List-post: <">>
Thats an awful lot of work for 500W. A pair of Svetlana 4CX400A's would 
double that.

I got 400W CW from an AM-6154 with under 10W drive, stable and reliable. 
About 300W for best SSB IMD. There are 3 different interchangable tubes 
that work in it.

Not interested in EME but the new amp loafs at 1500W using a mil surplus 
GE GL-51064 tetrode with 2500W plate dissipation that was used in a 350 
mHz 1000W output AM linear for the USAF Looking Glass project.

Obviously I prefer tetrodes for 432 since I cant justify an 8938 cost.

Another good 432 CW tube is the 7213 and there are several available 
cavities that tune without mods.


----- Original Message ----- 
From: "Larry" <>
To: "Robert Perdue" <>
Cc: <>
Sent: Tuesday, September 09, 2008 3:24 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
> _______________________________________________
> Amps mailing list

Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>