Subminiature valves / tubes
I came across a source for Russian valves (fdf surplus).
So far I only picked up a few 1Ж18Б ones. There would be boxes of 1Ж17Б as well. They're above eBay prices, but reasonably cheap and ready for pickup in a local store.
The unique structure of these tubes, which is based on electron-optic control of electron sheet beams originating in a capilary filament, confers them extraordinary performance and efficiency. These tubes were originally used only in Soviet military gear and were in use up until 1991 when the Soviet Union was dissolved. 5
Of course I know hardly anything about tubes, so everything here may just be a whole load of nonsense.
Do not exceed 1.2V filament. These are not 1.5V filaments. For NiMH battery which is a bit more voltage than a NiCd, a 10 Ohm series resistor gave about 1.17 to 1.2V on filament. 1
All direct heated filament/cathode and about 8mm to 10mm glass with anode on top wire. 2
For reliable longest life operate at less than 1.4V and more than 0.9V filament (not direct from Zinc, Alkaline, NiMH cells) and operate at less than maximum currents and voltages. 2 1Ж18Б = 1j18b rated to 60MHz, but may be usable over 100MHz. G3 internally connected to Cathode/Filament. These are cheapest and most available. Medium filament at 24mA. 2
General purpose Pentode, 1Ж18Б = 1j18b rated to 60MHz, but may be usable over 100MHz. G3 internally connected to Cathode/Filament, limits RF applications. These are cheapest and most available. Medium filament at 24mA. Will work as a triode using G2 as the Anode. 3
The base wiring diagrams are confusing till you realise they count cut off wires used for internal support/connection. e.g. 1j18b diagram shows 6 wires, but 3 and 4 don't exist, or are very short cut off stubs. So don't assume there are "snapped off" wires 3
With HT from 24V to 60V (suggested Maximum for 1j18b, though 90V works!) the 1j18b should be operated as a Pentode, as designed. 4
The 1j18b seems suited to operate as a triode at 9V to 22V. 4
...a small resistor in series with f- will reduce cold filament inrush and greatly lengthen life. Dropping about 0.2V to 0.25V appears to make little difference to performance, performance drops quickly below 0.8V though. 4
At low voltage the 1j18b gives best gain as triode with the anode top wire connected to ground (not to G2). In this configuration from 9V to 20V it's superior to Pentode mode. 4
Filament volts are not critical the valves seem happy between 1.0v-1.5v with best performance between 1.2 & 1.45v. The filament must be wired correctly with the dot on the valve connected to filament +. Bias can be obtained from either the - filament connection or a potential divider between the two, Filament + is taken as ground. 4
The 1j18b does work best as a triode via g2 with anode earthed, floating or connected to g2 depending on HT. 6
The internal structure should be very resistant to knocks and vibration. Glass envelope and mounting are naturally more fragile. Some document warned against bending the wires closer than 3mm from the glass. Using something as a heatsink on the wire while soldering might be a good idea.
There should be hardly any heat output.
NiMH seems a natural choice for heater (A) supply and the very reasonable B could be a stack of 9V or even 3V (CR2032 spotted) batteries. 24 V AC or 12..48 V DC supplies are common enough, though. I'm not sure how much you can starve these, but there's a design running with no extra B voltage off a single 1.2 V battery. Triode and gammatron configurations may be a way to go further.
The ground is common for A/B, but you can stack the B voltage if you can refer the B supply (battery) to the A line instead of GND.
I soldered one tube onto some breadboard and poked around with some resistors. Turns out I seem to be getting some amplification! >7x at 8 kHz(?) using +15V B+ and a NiMH plus 10 ohm at the filament if I have that right.
Links / reading
- 1Ж17Б data
- 1Ж18Б data
- 1Ж18Б prettier data pdf
- Russian tube directory
- 1Ж17Б @radiomuseum
- 1Ж18Б @radiomuseum
- submini article @radiomuseum
- UK Vintage radio thread
- Some articles in russian?
- Radio project
- Funky loop radio
- Also in Elektor 2010-10 Retronics column
- A nice parameter table
- hybrid preamp schematic Tonestack says guitar.
- AA thread
- "MIG" preamp for Hammonds (pdf)
- XFY 43 VFO