1J26A Rod Pentode

[Mike Watterson]

Sounds like a higher power variation of the 1j37b?
So the 1j37b may have replaced it.

I wonder is it usable with 0.65 V filament? i.e. two in series. If I get bored of writing I might order some and take a look. I suspect more a collectors item (Joe Sousa?) than useful for projects.

I think a cache of 1L6 valves is more likely to be in demand in the future.

[Murphyv310]

I agree with you re the 1L6.
I also think these are more of a collectors item too.
I might be persuaded to part with one or two, certainly to cover my costs.

[BusyBee]

The 1L6 looks a useful valve although for my purposes I don't go for combined mixer oscillator types. One glance online at prices did tend to put me off somewhat further. I will happily leave them to their original equipment.

Tracy

[Mike Watterson]

The 1L6 looks a useful valve although for my purposes I don't go for combined mixer oscillator types. One glance online at prices did tend to put me off somewhat further. I will happily leave them to their original equipment.

Tracy

The DK92 is just as good and a fraction of the price, maybe 1/20th. The 1L6 was mentioned because they are artificially expensive, and hoarded because the Zenith & other World Bands portable USA sets use them. The DK92 will work directly, but all the HF bands need realigned. Even some ordinary USA sets used the 1L6

[Mike Watterson]

Joe Sousa brought this ЭМ-10 rod tube to my attention:
https://www.ebay.com/itm/322895472704
https://www.radiomuseum.org/tubes/tube_eem-10.html

About 17 mA @ 0.7V. Notice the shield at the base? It's for electrometer or other very high impedance applications. Though the 1j42a and 1j24b are good too.

I found this Electrometer schematic years ago on a NASA web site.
   

[Mike Watterson]

That seller also has ЭМ-7 and ЭМ-8, but they may be just miniature triodes? 18mA @ 1V
Also has a nice selection of real barretters (Series current regulators using iron filaments in a hydrogen atmosphere). A regular thermistor may be needed in series to limit inrush current.
There is also a UHF acorn valve, 6D4J 6D4ZH 6Д4Ж. However it's just a diode. https://www.radiomuseum.org/tubes/tube_6d4j.html
They were invented in the 1930s but very difficult to make so the B7G base replaced the package. https://www.ebay.com/itm/323390878978

[BusyBee]

Joe Sousa brought this ЭМ-10 rod tube to my attention:
https://www.ebay.com/itm/322895472704
https://www.radiomuseum.org/tubes/tube_eem-10.html

About 17 mA @ 0.7V. Notice the shield at the base? It's for electrometer or other very high impedance applications. Though the 1j42a and 1j24b are good too.

I found this Electrometer schematic years ago on a NASA web site.

I too have that Nasa schematic. I also have a copy of the document that it came from, if anyone is interested. It does show four circuits, if I remember rightly. One uses the эм7 which you mention in your next post. This is a electrometer triode with 1V 18mA heater. These valves may be a little limited though, for normal purposes, as they are designed for low grid current etc and end up having very low gm. They are designed for very low voltage use though. эм7 - Anode 7V.

Tracy

[Mike Watterson]

I too have that Nasa schematic. I also have a copy of the document that it came from, if anyone is interested. It does show four circuits, if I remember rightly.

Yes, please.

But you could run two with filament in series, 16 mA to 18 mA and the gm is squared.

I did a very low power TRF AM radio once by using very low collector currents, which means low gain, but the gains multiply and the currents add. Ran for over a month with no on/off and a crystal earphone off an AAA cell. Matchbox, small rod aerial and no aerial wire. MW & LW. Penalty is it's noisier.

[Murphyv310]

Me too if that's possible Tracy.

[Murphyv310]

Hi.

Some info here from my friend in Poland. Nothing new unfortunately but perhaps worth sharing.

EDIT. I have a zip file but the forum software is rejecting it.
PM emails and I'll forward it that way.