Thanks for the input Carl. I had a few follow up questions if you don't
mind.
>> Adding individual bias circuit may be an option, but
>
>> raises the cost.
>>
>
> See above. One pot, resistor and bypass cap..
Showing my ignorance...so the grid bias is fed through a choke and then
"added" with the exciter signal. It's then split off to each grid feeding
through a 2.7ohm resistor. Are we replacing R45 and R46 with a pot and a
fixed resistor of the same value or are we making some kind of a voltage
divider for one feed? If so, I can't think where we want a bypass cap.
Obviously I'm in the weeds here.
>
>
> For the same power plus 160M and WARC find a LK-500ZC. I havent been able
> to kill mine. Id stay away from the AL-1200 due to tube cost and a rumor (so
> far) that the 3CX1200 series are being discontinued.
Got an ebay alert set up for that amp now
>
> I converted a 2000 for George Badger at Svetlana years ago using their
> 4CX400A. Except for filaments (run them in series) and socket its plug and
> play and much more rugged than the 8122. Better production tolerance
> resulting in minimal bias tolerance range also. Others have gone with a
> single 3CX/3CPX800A7 as its the same socket.
Just so I understand ( in the case of the 3cpx800a7), I'd be converting from
a grid driven tetrode to a grounded grid/cathode driven triode? The reason
I ask is that even the 4cx400's are getting hard to find, and with a single
tube, I'd also not have the matching issue.
> Another good amp is an Alpha 76 3 holer with good or bad tubes as the
> prices are way down. Run the good tubes until they die and then go with a
> pair of 3CPX800A7 pulls.
It seems that there was a 2 hole version too. Again, I've got a ebay search
running, and now that ham fest season has started I'll keep a close eye out
for those two amps.
Thanks
jim W6JMF
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