Kinda OT: Swan Mark I Linear expected output on 4-400A's in G-G?

[Bob, WB2UJD]

Thank you everyone for the reponses on my amp question.  I have just returned
from vacation and will ponder them.

A couple of initial comments:

About dropping the 4-400A in a 3-400z (or 3-500z) circuit and the grid
connections.  The 3-400z and 3-500z triodes single grid connects to pins 2, 3
and 4.  In the 4-400A, pin 3 is Grid 1 (screen?) and pins 2 and 4 are grid 2
(control?).  I assume in most 3-400z or 3-500z amps, all three grid pins are
grounded.  This is the case in my Mark I.  This being the case, simply
plugging in the 4-400A tubes causes both grids to be connected to ground.  Am
I missing something?

Regarding the difference in tube heights, I had to make modifications to the
amp to properly accomodate the 4-400A's and from what I read in the data
sheets, the same would have been required for the 3-500z's.  I cut holes
under the tube sockets and decreased the socket spacer height to accomplish
this.  I had thought about mounting the ceramic sockets flush on the top of
the chassis, but was advised against doing this to avoid pin cooling problems
(since the amp cross cooled with no chimneys or forced air sockets, just
plain old ceramic sockets).

Lastly, why I haven't just picked up a pair of 3-500z's.  I'm CHEAP!!  I
haven't been able to bring myself to plunk down $250 for some graphite jobs
and good used ones run almost the same (anyone with good used 3-500z's at a
reasonable price, let me know!).  No, I am not so old that I have a shack
full of 4-400A's (I'm 42) but they can be found on Ebay and such.  The
Amperex ones I have were given to me by a local ham many years ago.  I only
recently restored the amp and have set about trying to determine what I have
ended up with and if it is performing as well as might be expected and what
it might be good for (CW, SSB, both?).  I will have to get my recently
acquired SB-610 (along with the SB-102 or HW-101's) connected up and try to
determine how clean the power I am getting on the two plate voltages is (on
SSB of course).  I wouldn't want my return to HF operation to be with a
sloppy QRO signal!

Again, thank you all for your thoughts and advice.  This is a great group.

Bob, WB2UJD

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