Thats an awful lot of work for 500W. A pair of Svetlana 4CX400A's would
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" <email@example.com>
To: "Robert Perdue" <firstname.lastname@example.org>
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
> 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
> run away and self destruct.
> Good luck.
> Larry - W7IUV
> 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
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