Tube mounting position

[piero7]

Anyone could explain me what that mean? I can mount this tube horizontally but "with pin 1 and 8 in vertical plane"

Pins 1 and 8 are heater

[Wavebourn]

That means that the manufacturer refuses to accept claims about damaged tube if it was not mounted according to their specifications.

[Geek]

It means with direct heated cathodes, over time the heater will sag if it's mounted horizontal otherwise and cause grief.

Even some indirect heated power tubes specify vertical mounting (H-sweeps).

Cheers!

[Hearinspace]

Originally posted by piero7
Anyone could explain me what that mean? I can mount this tube horizontally but "with pin 1 and 8 in vertical plane"

Pins 1 and 8 are heater

Red to white hot filaments can sag over time. In the structure of some tubes, there is the possibility that if incorrectly oriented with respect to gravity, the heated filament can sag far enough that it comes into electrical (not necessarily physical) contact with another element - usually the grid - causing an electrical short. In the data sheet the tube specified is built such that when the two heater pins are aligned vertically the planes occupied by both grid and filament are too - insuring that as the filament sags downward it does so within its own plane - not changing distance relative to the grid .

I have used the principal the opposite way to save tubes that were discarded due to arc on start-up by rotating them so that the filament sags in the direction opposite to its distorted shape - curing the arcing problem. You can't do this with commercial gear or circuits you are building for use by anybody other than yourself but when it's a rare tube on the garage/shop clip-leaded breadboard amp it's just fine.

[piero7]

Mounting direct heating vertical, in conclusion, is a better idea.

Thanks to all

[pointy]

sometime the wires outside the tube will become soft when hot

so if the wires run level in the same plan as the tube they can short

therefore you need to bring the wires to the socket so they will not short when they are hot and soft

[kevinkr]

Originally posted by pointy
sometime the wires outside the tube will become soft when hot

so if the wires run level in the same plan as the tube they can short

therefore you need to bring the wires to the socket so they will not short when they are hot and soft

Better to just use wire with an adequate insulation temperature rating if I understand what you are on about. Teflon or irradiated PVC types are what I use and they will not melt at 200 degrees C in a lot of cases. (Nothing inside an amplifier should ever be that hot! )

[pointy]

yes but that is what the datasheet means......................!

[kevinkr]

Originally posted by pointy
yes but that is what the datasheet means......................!

No it's not... The data sheet talks about the internal alignment of the filament and other structures. (INTERNAL grid and filament sag are the actual concern.) You need to reread it a bit more carefully.

[pointy]

Spaghetti