[Henry] Henry 2K-3 amplifier problem

[john w. king]

    I have a henry 2K-e amplifier with two 30500Z tubes and am having
trouble getting the filaments to light up in both tubes.

I replaced the filament pins on the left tube socket facing the front of the
amplifier. The left tube did not light up, so I replaced the pins on the
tube socket.

I then fired up the amplifier and guess what................. the left tube
lit up, but now the right tube did not light up .

Suspecting that the right tube might be defective, I replaced the tube and
GUESS WHAT.......the left tube did not light up, but the right one now lit
up..

As you know, the filaments are in SERIES and the puzzle is why one will
light up and the other will not. Additionally I am puzzled  as to why one
tube will light up  and one will not and then when the dark tube is
replaced, the the one that originally lit up will no longer lightup.

Has anyone had experience with this mysterious problem that has me puzzled?
Thanks for any assistance or suggestions. 73, john, K5PGW