Hi all, just a few notes regarding the GI-7B, BT and GI-6B triodes....I
am currently running a pair of GI7BT tubes in a homebrew 80-10 meter
amplifier....These tubes are little gems particularly if you take the
trouble to set them up correctly and pay attention to cooling..I am
running 2500vdc under load at 800ma carrier for around 1150 watts
output....I have my grid trip set at 180ma but to date it hasn't had to
activate....
In regards to cooling....I note many of the conversions use a common
muffin fan blowing air over the standard GI-7B coolers....I am very
sceptical that this is a very effective way of cooling these tubes and
would guess that they would be running near their heat limit...I chose
to install a compact squirrell cage blower into the amplifier when I was
constructing it...It is rated at 60cfm Jap built, picked up at a
swapfest....
I took the original coolers off the GI-7BT tubes and replaced them with
coolers from GI-46B tubes...The GI-46B coolers are an excellent
substitute and far superior to the standard cast alloy
coolers....Finding spare 46B coolers may be a bit difficult...I was
lucky enough to have a friend in Europe who sourced some for me....
I hope this information is of use.....
73 de Bob..VK3ZL..
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