Small (Novel) Tube Rectifiers?

[Kashmire]

I've used the 6CA4/EZ81 9-pin tube rectifier with great success. It is cheap, readily available, in current manufacture, and works great.

However, I'm working on a project needing something physically smaller that generates a bit less heat (it will be in a non-ventilated enclosure). The EZ81 filament consumes 1A at 6.3V. Compare that to a 12AX7, which consumes only 0.3A at 6.3V. So a valve rectifier approximately the same size as a 12A*7 valve would be perfect.

I only need 20-40mA. Does anyone have recommendations for a small, cheap, and available rectifier valve?

[Bandersnatch]

hey-Hey!!!,
Type 26Z5 is the right size but consumes 0.8A 6.3V equivalent. It is probably not one of the inexpensive ones either.
cheers,
Douglas

[rotaspec]

Maybe it's little brother, the EZ80/6V4. If is down to 0.6A.
Personally, I wouldn't run any tube in a non-ventilated enclosure. They work, but the tubes won't last.
Do you HAVE to run a tube rectifier?

Gary

[HollowState]

6X4 or 12X4. 0.6A or 0.3A filament respectively.

[Ty_Bower]

If low cost, small size and minimal waste heat are your primary design criteria, perhaps you could consider solid state rectification. A pair of UF4007 should do the job nicely?

[trigger]

i have seen miniature type versions of triodes like 12ax7, i always thought if there were miniature type rectifiers and beam power, a minature tube amp would be novel

sorry a bit of topic

[analog_sa]

If the current is so low why not use a small triode as a rectifier?

[rman]

The 6x4 runs cool, and does not need a separate filament supply to itself, but I agree with Gary about not using tubes in non ventilated box.

Cheers.
Rolf.

[wa2ise]

If it's in an unventilated box, that likely means you can't see the nice glow of its heater, and thus no eye candy, so you might as well go SS for the rectifier.

I wouldn't worry about cathode stripping, that's only an issue in high powered equipment like 50KW radio station transmitters or radar installations.

[Eli Duttman]

Originally Posted by Kashmire

I've used the 6CA4/EZ81 9-pin tube rectifier with great success. It is cheap, readily available, in current manufacture, and works great.

However, I'm working on a project needing something physically smaller that generates a bit less heat (it will be in a non-ventilated enclosure). The EZ81 filament consumes 1A at 6.3V. Compare that to a 12AX7, which consumes only 0.3A at 6.3V. So a valve rectifier approximately the same size as a 12A*7 valve would be perfect.

I only need 20-40mA. Does anyone have recommendations for a small, cheap, and available rectifier valve?

You can squeeze 20 mA. out of a 6AL5. As the data sheet shows, PIV is low at 330 V. So, use either a hybrid Grätz bridge or the arrangement I call "cockeyed bridge", depending on the power trafo you employ, in the setup.

I agree with the previous remarks about allowing for some ventilation. A few strategically placed holes will provide enough air flow for cool running types, like the 12AX7 and the 6AL5.