Experimenting with 1j18b

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Apr 292014
 

Experimenting with Russian Rod Pentodes

Here is Russian 1j18b (aka 1zh18b, 1sh18b really 1Ж18Б ) on IC breadboard. The 1j24b and 1j29b are actually better purchases.

Testing 5.4MHz Hartley Oscillator at 16V and 25V.

Dscf2010

1j18b with 1.2V NiMH for filament and  +15V to +32V test bench PSU

This valve concept  was invented in 1950s but many models only entered production in early 1960s and used up to 1980s in MIG fighters and portable Military radio. Superior frequency response to many Germanium transistors (120MHz vs 3MHz), more stable, high impedance lack of Silicon Transistor production is many the reason for long term use. No recorded Domestic/Consumer application.

Heater filament power is from 12mW to 50mW depending on model compared with 2000mW for typical US/European domestic valves (tubes). Recommended HT typically 45V (max 60V) to 150V for 4W “transmitter” versions. But operation at 16V upwards is definitely feasible. Apart from the 4W models, the valves are so low power that in some application circuit the power consumption is similar to transistors and the valves can be mounted direct on PCB or stripboard (veroboard). The 1j37 is unusual as although it has single anode it has dual control grids at the same place. Read the Radio Museum article to see how this is possible. Regular valves with a single anode and cathode can’t be made like that. It is like a dual gate depletion mode cascode MOSFET. (A pentode with suitable voltages on the 3 grids behaves like cascode circuit. I think the 1j37b is a pentode with a 2nd identical control grid, not a hexode)

Original circuit from German Website (scroll down)

hartley_orig_dl1adr

For operation at 16V to 32V move R1 grid bias from ground (f-) to +1.2V (f+), makes grid closer to 0V of cathode.

Do not exceed filament)”>filament)”>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.

See Radio Museum Article

Dscf2009

5.4MHz, 3V RMS on 25V HT (about 1V RMS on 16V HT)

Grounding the Anode and using G2 as anode with 42V HT operation as a Colpits oscillator up to 100MHz is possible. So using it as a triode is possible,