Battery-heater subminiature diodes.

[G6Tanuki]

These never seem to have been a 'thing' - I'm thinking here of the little double-ended glass types for use at VHF.

The EA50 allegedly had a rare sibling the DA50 but its heater-consumption was rather high; it seems a lot of applications like RF field-strength-indicators/wavemeters used a diode-strapped pentode like the 1S5 or 1T4.

Which seems wasteful particularly in the context of WWII usage.

So why I wonder was there never a little B3-style VHF glass diode that would take, let's say, 25mA at 1.4V and work up to a couple of hundred MHz?

[pmmunro]

This was apparently designed for radar use, but not quite what you wre looking for.

http://www.r-type.org/exhib/acl0322.htm

PMM

[G6Tanuki]

4V 0.2A heater... yes it's not going to work well in a hand-held field-strength-meter/wavemeter powered by a single flashlight battery...

The DA50 took 0.3A at 1.2V so would still drain a single battery rather fast.


The later B7G DA101 took only 50mA at 1.25V so is closer to my idea.

https://www.radiomuseum.org/tubes/tube_da101.html

Of course all were obsoleted in the early-50s with the coming of cheap Germanium diodes.

[Philips210]

Just the other day I came across a EA50 amongst several TV/radio valves and wondered what use could be made of it.
For those that haven't seen one please see attached pic.

Regards,
Symon

[G6Tanuki]

I wonder if you could use it in a perversely-retro valve-powered crystal-set?


The EA50 was used extensively as sound- and vision-demodulators and peak-limiters [to remove car-ignition/motor-commutator spikes which otherwise caused crackles and transverse stripes of white-dots] in the first generation of TV receivers; it also found service in a whole bunch of WWII RADAR systems.

I guess it was equivalent to the likes of the OA81/1N34A Germanium-diodes which followed.

I've got an EA50 somewhere, along with a 'low-loss' ceramic holder for it.

[paulsherwin]

The EA50 and CV equivalent were sold off in huge quantities after the war, and apparently cost pennies for dozens. They turn up in all sorts of 50s hobbyist gear and projects. They can be used as HT rectifiers if the current is low - I have a 2 valve sig gen that uses one (all the other components look government surplus too). It doesn't use a holder, it's just soldered in.

[Philips210]

Originally Posted by G6Tanuki

I wonder if you could use it in a perversely-retro valve-powered crystal-set?

Very good!

Symon

[kalee20]

There's the 1A3 in B7G, 1.4V 150mA... but it is indirectly heated so you have the luxury of a floating cathode!

[joebog1]

Are not EA50's used as rectifiers in a multitude of VTVM's ?. In the probe itself.

Joe

[G6Tanuki]

Originally Posted by joebog1

Are not EA50's used as rectifiers in a multitude of VTVM's ?. In the probe itself.

Joe

Yes - the low [and repeatedly-predictable] stray-capacitance of the EA50 along with its slender build made it a good choice to build into RF VTVM probe-heads.

The ones I encountered usually fed the probe-tip to the EA50 anode through a high-voltage-rated low-value capacitor - typically a few tens of pF - which was calculated to work with the EA50's stray-capacitance as a RF potential-divider.

Worked well, up to around 50MHz.