[AMPS] Henry 3KA console - tube filament problem

[KA2YKC@aol.com]

Hello all;

I am attempting to repair a Henry 3kA console with a pair of 3-500Z's for a 
friend.   Only the left side tube's filament is lighting. The right side is 
stone-cold. 

Doing an A/B swap still results in the right side not lighting. Pulling the 
right (unlit) tube, the left tube still lights. 

After pulling the tubes, I inspected the tube sockets. All looks OK. I took 
some measurements with an ohmmeter, and pin5 of left tube has a good 
connection to pin1 of right tube. Pin1 of the left tube and Pin5 of the right 
tube have good continuity to the filament transformer. I measured less than 
10 ohms on the secondary of the filament transformer when totally 
disconnected via the jones connection. My next step is to wire the meter to 
each socket and take some voltage measurements with power applied. Stopped 
short there last night as I was getting too tired and didn't feel like making 
a deadly mistake due to fatigue. 

Before I dig deeper and pull the RF deck off the console for further 
inspection (the tube socket base assy is a bear to get to!), does anyone have 
any suggestions ?

Is it possible for the one tube to light without the other tube in place 
(like the old christmas lights where one bulb out causes the rest to go out) 
? It appears they are wired in series, but is it possible the transformer has 
an opening on one side of the secondary, and I am getting a return to ground 
via another path? (I checked the caps to ground from the fil. pins, and all 
are ok)  Gave up last night, maybe I am missing something too obvious ??


TIA for any suggestions.

73 Eric
KK2ED (ex ka2ykc)


 

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