[Henry] Filaments in 2KD3

[John King]

I found the problem with absent HV in my 2KD 3 Henry Amp. Turned out to be a bad meter. .
NOW to another problem !!! Only the right tube lights up with filaments. I have four (4) good Eimac  3-500 Z tubes and no matter which of the four tubes I plug into the left tube socket the left one never lights up. I also have a NEW Machlett tube that I have plugged in and the filament on the left does not light up OF COURSE, I HAVE THE HIGH VOLTAGE UNPLUGGED FROM THE AMP!!!!
Besides substituting tubes, I have done the following:
1 The tube sockets have recently been replaced with NEW ceramic sockets.
2. I have cleaned the filament pins on the sockets and tube pins with De OXIT and Q Tips.
3. I have measured the  AC filament voltage at the tubes with a tube plugged into the right socket and measured 5.7 VAC on the right filaments with right tube lit up.
4. I have measured the AC filament voltage t the left tube socket without a tube inserted and measured 7.2 VAC while the right tube filament is lit SHOWING 5.7VAC.
Series filaments belong in CB amplifiers and 1950 television sets in my amateur opinion although Henry explains their thought about that in the manual.
I wonder if the capacitor between the filaments could be open and causing the problem?
Have any of you had such a problem with the 3-500 Z in series in a Henry amplifier?  I know of CB types who have run them so hot that the solder in the pins melted and ran out of the pin. The pins of these five 3-500 Z tubes are GOOD and have never been run hot enough to melt solder.
Your input based on your knowledge and actual experience will be greatly appreciated.
Thanks and 73, John, K5PGW