[Amps] GI-46B Revisited..

Robert Briggs vk3zl at bigpond.com
Wed Jan 16 03:50:51 EST 2013

Gidday all..I have built around 25 VHF amplifiers over the past three 
years using the Russian triodes, GS-35 and 31B tubes as well as GI-6 and 
7B tubes..All of these amplifiers are in daily service on 6 and 2 meters 
and trouble free..

I have looked through all the information on the GI-46B tube and a few 
things don't add up..A company in Europe uses these tubes in their 
amplifier product's..I also see many retro fits in You Tube clips for 
TL-922 and Heathkit amplifiers replacing the 3-500Z and supposed power 
outputs of 1600 watts..

Just taking the TL922 conversion to GI-46B tubes as an example the tubes 
are openly mounted with GI-7B coolers in place of the GI-46B 
coolers..These film  clips show the TL-922 cooling fan retained blowing 
against the tubes..I question how are they getting rid of all the heat 
produced with such a pissy set up..I would have thought the tubes should 
be set up mounted in a box construction and pressurised with a good 
blower, chimneys etc..The mind boggles..

According to the Russian GI-46B specifications the tube is only rated at 
350 watts anode dissipation..Most of these conversions will be running 
at close to 3kv and to produce 1500 watts output even at 55%  efficiency 
a pair of tubes will have to be dissipating a lot more heat than the 
tube anode ratings..

Obviously the sketchy information for the GI-46B supplied on the Russian 
spec sheet must be very conservative..

I am wondering if there are any members on this reflector have used the 
GI-46B triode as in an amplifier or a retrofit conversion and what the 
real results are and also the cooling used..I am about to build a pair 
of amplifiers 6 and 2 meters using the GI-46B tube for a client..I am 
confident that with proper attention to cooling etc that the amplifiers 
will turn out ok..


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