Quote:
Originally Posted by ms660
The UU6 is indirectly heated, the cathode is not the filament, the cathode just so happens to be connected to it.
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That's my recollection too, of the UU6. I had one with a loose base.
It is more than academic - the heater has two wires (of course) and the cathode has its own leadout. The cathode leadout is shoved down inside one of the pins, together with the heater leadout, so this pin will actually have TWO wires soldered to its end.
If you clean it and just see one wire, you might be tempted to solder it up and think there's a job well done, not realising that the other wire should be there (maybe cut a bit short in the factory).
If the wire not connected is the heater, it's not going to work and you might mistakenly bin it then. If the wire not connected is the cathode, it might possibly work if the heater/cathode insulation then fails, establishing a connection to the cathode tubes. But it's hardly going to be reliable.