Hey Dan. I have one Alpha 76 which is performing very well with a pair of
3CX800's. W4MA (Bill Burnett) is the owner. Electronically the 78 and 374A
should work just as well...it's the physical part I'm not sure about. In
the 76 I remove the middle tube and seal the hole. The existing front and
rear sockets are used for the 800's. On the 78 and 374A the tank coil is
closer to the front socket and may cause a problem with the rubber chimney
which looks almost identical to the 86 and 87A chimney.
It seems the air flow is sufficient without any alterations if the power
level is held to 1500 watts. The amplifier is capable of a little more
output with these bottles but I wouldn't advise it. After all, the limit is
1500 here in the states.
The filament voltage is easily boosted to the proper voltage with an
additional transformer located beneath the PC board. It all goes together
very nicely.
I'm not ready to start releasing kits just yet. I need to get a few more
units going here in the Atlanta area to make sure all is ok.
The biggest problem right now is cost and availability of 3CX800's. The
Eimac factory has consolodated to California and this has caused a shortage
of product for the time being. I've had 4CX250's on back order for my
broadcast station for two months from Harris Corporation. I'm told by
discount tube distributors the price is now $410 each for the 3CX800's.
Bill and I located a few 'pulls' for $230 each. That situation is almost as
bad as the 8874 dilemma.
CUL, 73, Dick
Hello Dick, good to see you up here lurking about. Trust you are doing
well, wondered if you have done any of the 3CX800 conversions yet?
CUL, Dan, W4EA (ex.N4DVW)
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