Heater Wiring Question

[Papa Jim]

Curious about a 5F2 Princeton I just completed that I modded for more sound options. It uses only half of two different preamp tubes. 12AY7, and a 5157 at the moment. I didn't even think about it and wired both heaters up in each of theses tubes. Doe's it matter to power a heater in the 1/2 of a tube not being used 

[Willabe]

Doe's it matter to power a heater in the 1/2 of a tube not being used 

No.

[Papa Jim]

ok thanks. I'll leave it powered as is then.

[pdf64]

The unused sections will tend to develop cathode interface resistance aka sleeping sickness and lose emission. Akin to leaving tubes on standby forever, ie the preamps at least would die more quickly than if HT was also energised.
Tomer explains it http://www.tubebooks.org/Books/Atwood/Tomer%201960%20Getting%20the%20Most%20Out%20of%20Vacuum%20Tubes.pdf
So best to not connect the heater for an unused section.
Alternatively, to save messing with the heater wiring, with those sections perhaps wire grid to cathode to 0V and feed them with 1M plate loads, so that a trickle current keeps them ticking over? It could mostly all be done p2p on the tube socket terminals, to avoid using turrets etc.

[Papa Jim]

Sounds good... For the short term I am gonna clip my little jumpers between the used and unused heater terminal at the socket. Next time I am in there for any mods which probably wont be long I will take your advice. Anything to protect the tubes is good. Thanks

[Willabe]

The unused sections will tend to develop cathode interface resistance aka sleeping sickness and lose emission. Akin to leaving tubes on standby forever, ie the preamps at least would die more quickly than if HT was also energised.

Doesn't matter if he's not using that triode, and he's not.

[Papa Jim]

Not a single wire is connected to that half except the filament jumper from the used half.

[Papa Jim]

sorry if I didn't make that clear Pdf64.

[pdf64]

...Doesn't matter if he's not using that triode, and he's not.

Just to be clear, if that tube is never going removed from that socket then heating or not heating the unused section makes no difference 
I think that the AA165 Bassman looks to heat the unused section of V2 https://el34world.com/charts/Schematics/files/Fender/Fender_bassman_aa165_layout.pdf
But if the performance of unused section is to be preserved (ie cathode interface resistance avoided), then it's heater should not be energised.

[PRR]

AFAIK, sleeping sickness is reversible. Run the tube with bias for an hour. True, the initial impression is "sick", but it recovers.

The history of sleeping sickness is convoluted. Early tube work never ran tubes no-current (what use is that?). Tube computers however could have digits that stayed zero for long periods. The million-dollar digit in a $100,000 budget. The day that last digit is needed, it doesn't want to take its One. This was a big deal. The initial fix mostly went to impurities in the Cathode Nickel (you need some, not others). The total tube industry's need for cathode nickel was a fly-speck in US Nickel's daily production, but it was a Critical Resource. Government, tube makers, and the nickel syndicate had already agreed that one large ton of special-brew nickel, tested by tube makers, would be THE nickel for the year. So the sleeping sickness cure covered all receiving tubes of that era.

Ah, but yes, nobody builds tube computers anymore, metallurgy and its market have changed. Perhaps new-made tubes do get sleeping sickness? Or maybe the magic mix is now so easy that you just check some boxes on the nickel order? I dunno. I do not think I have seen forum trouble-stories explainable by sleeping sickness. Of course forum tales are few and often confused. However I have seen posts about long-stored vintage tubes starting poorly and coming to full life after some hot-time.

Agree that it costs about nothing to throw a 220k-1Meg plate to B+ to keep the juice flowing.

[shooter]

nobody builds tube computers anymore

as infuriating as mine has been the last 36hrs I might give it a go! 
but it looks like I killed the infection - for now