Valve F3A3 - what are they?

[jimscoper]

Tempted into buying a box of old valves - hiding in a mouse-eaten brown envelope were 5 items that look like early transistors. Marked Valve F3A3.

Flattish copper can about 10mm long and 2mm thick 6mm wide with four wires and a green paint band. Not taken an AVO to them yet. Any ideas?

The other stuff was wire ended CV valves plus a few conventional types and a couple of acorns. Nothing really weird.

Had promised myself no more radio projects, but I feel a super-regen coming on.

[Jon_G4MDC]

Had some devices that answered that description.

Very early Germanium transistors. PNP most likely. I don't think I ever did anything with them and I know I no longer have them.

Try the meter?

[jimscoper]

Tried the AVO. A dead short between the two outer wires, 25 ohms between the two inner wires and infinity between the inner and outer pair. Symmetrical, no sign of any semiconductor diode effect.

So maybe a very small vacuum diode or maybe some sort of thermocouple.

Did try my digital multimeter, measuring the middle two pins (filament?) the reading climbed rapidly but on higher ranges came to 15 ohms. Suspect its a diode. Very small though, transistor size. Further tests to come.

[Cobaltblue]

Some pictures would be nice.

They seem awfully thin to be a valve but the term Valve electronic was used for solid state devices as well.

Interesting devices.

Cheers

Mike T

Do they all measure the same? I think they are early generation transistors with the can soldered up, is the base a bit bigger than the top? If so plonk a soldering iron on one for a bit and lift the lid, it will be interesting to see the insides.

[Julesomega]

Can't see anything on Mister Transistor's Historic Semiconductors but I'm sure he would like some images from you

[Refugee]

Here is one with a lot more photos.
http://semiconductormuseum.com/Museum_Index.htm

[jimscoper]

Photo now in my album F3A3 Valve.

Opened one up. It is a vacuum? diode. Filament in inverted V surrounded by a grid. No glass except for seal, copper cap soldered on (under vacuum?).

Dimensions 12mm long 5.5mm wide and 3.9mm thick.

Perhaps the last gasp of the sub min valve business.

Oh, pictures please...

Looked at the pictures, amazing!

[Graham G3ZVT]

Pictures are in the OP's profile.
Anything with a handwritten serial number on the packaging must be rather special.

[matthewhouse]

Wow, certainly looks like a little metal valve! Any chance of a close up of the internal construction?

[jimscoper]

One of the pics in album does show the internals. I'll try to do a better one.

I found an extra bag with one F3A3XE in it. I then rigged up a filament/bias supply and tried one of each type out. Clipped to the copper can as an anode because the wound wire 'grid' did not make any sense as a diode. Both work!! At Va=25 volts with Vg=-0.5 the F3A3 conducts 25uA. This drops to 4.5uA with Vg=-1.0. A gain of 24uA/volt for a triode. Typical characteristic curves for both.

The F3A3XE conducts 31uA at Vg=-0.5 and 9uA at Vg=-1.0. A gain of 44uA/volt. This was with an anode resistor of 68K and 1.5volts on the filament.

I had hoped the XE version would be some sort of thyratron (XFG1 type) but even though I swung the HT up to 60 volts (Vg=-2.0) nothing odd happened. So now back in the box.

[HamishBoxer]

Where these the "Hearing Aid" valves from the 50,s? No, I must be wrong looking at above picture.

[G6Tanuki]

I don't see these as 'hearing-aid' valves, they look much more like something designed to be used in military/avionics applications.

The 'hearing aid' valves were glass-encapsulated things like the DF70 -

https://www.radiomuseum.org/tubes/tube_cv386.html

[jimscoper]

I reckon G5Tanuki is right - military. The other valves in this box were wire ended CV476,CV4502,VX813X,EA50,VX8123 and others. Plus a few R17 rectifiers and some paxolin tube high voltage rectifiers. I got these in Maidstone, maybe these were from Marconi Rochester - or not.

I have uploaded some more pictures into my album 'F3A3 under microscope' - my technique is not all that good. Sorry about the solder splashes on the grid, came from taking the copper cap off, bit wary of picking them off.

I am curious as to date. By the mid 1950s it must have been clear transistors were the way forward. Maybe tiny valves were seen as radiation-proof. Anyway the military were into valves well into the '60s. My guess for these things is 1965 or so.

[VT FUSE]

Further back in this thread you said that you hoped that the testing would reveal a device such as a Thyratron like XFG1 (HIVAC)

I can let you have a WW2 General Electric 2D29 Ordnance proximity sub mini wire ended Thyratron, only don't believe Radiomuseum where it is referred to as a cold cathode device,the filament is rated at 1Volt and something like 60-100mA
should you like to experiment.

Regards Mike

[turretslug]

Electrometer triode?

[barretter]

Originally Posted by jimscoper

One of the pics in album does show the internals. I'll try to do a better one.

I found an extra bag with one F3A3XE in it. I then rigged up a filament/bias supply and tried one of each type out. Clipped to the copper can as an anode because the wound wire 'grid' did not make any sense as a diode. Both work!! At Va=25 volts with Vg=-0.5 the F3A3 conducts 25uA. This drops to 4.5uA with Vg=-1.0. A gain of 24uA/volt for a triode. Typical characteristic curves for both.

The F3A3XE conducts 31uA at Vg=-0.5 and 9uA at Vg=-1.0. A gain of 44uA/volt. This was with an anode resistor of 68K and 1.5volts on the filament.

I had hoped the XE version would be some sort of thyratron (XFG1 type) but even though I swung the HT up to 60 volts (Vg=-2.0) nothing odd happened. So now back in the box.

What you have measured is transconductance not gain. It's very low for a normal valve but might be in the ballpark for an electrometer tride as Turretslug suggests but it's hard to believe it's a valve if there is no internal glass bulb to maintain a vacuum.

[Radio Wrangler]

Very little glass, rugged, very small, low voltage heater, not seen in quantity, looks expensive....

It would have to be for something where size was critical. I wonder if we're looking at a special device for shell fuzes? or air-to-air missiles? Having very light structures is one way to handle high acceleration.

David