Comparison of electron tubes with Pleiades pull up bias

This is just on measuring anode current for low anode potentials.


(Attention to safety. A fuse should always be used in series with a battery.)


E88CC Mullard
Heater voltage = 5V
As cathode temperature is increasing Vg reaches -600mV or more.
With pull up bias resistor Rag=10ΜΩ, Vb=12V
Ia is 300μA
At Vb=24V, Ia=2mA
At Vb=36V, Ia=4.5mA
(Va almost coincides with Vb as on most of these experiments no load resistors are used. Headphones coils, tape recording head coils, transformer could are used. Also since inductors generate EMF output voltage can be double the Vb supply).


Note: As cathode starts emitting the free electrons it begins becoming positive with respect to grid by the positive protons left behind. This is possibly the reason why grid is negative with respect to cathode. The actual negativeness of grid is greater. The readings shown were taken with a 1GΩ to 10ΜΩ digital voltmeter. If a very high impedance electrometer or pH meter is used the grid is measured more negative by a few hundred more millivolts.


In order to make the grid less negative a pull up Pleiades bias resitor of 10MΩ from anode grid was connected. This increases anode current and makes operation possible, see previous posts.


On the following electron tubes 12V were connected to heaters and 10MΩ from anode to grid unless otherwise stated.


ECC83 Tungsram
Vg=-777mV
Vb=12V, Ia=2μA (3μA when cathode is colder before Ia fades to 0)
Other Tungsram ECC83 measured 4μA
Vb=24V, Ia=23μA,
other Tungsram ECC83 Ia=41μA
Vb=36V, Ia=105μA, 108μA at slightly lower cathode temperature
other Tungsram ECC83 Ia=172μA


Mystery electron tube, it was found inside a Tungsram ECC83 box, it reads Philips ECC8?
Vb=12V, Ia=23μA
Vb=24V, Ia=126μA
Vb=36V, Ia=330μA


ECC82 Ei (Yugoslavia)
Ia=500μA
1.6mA
3mA


EF183 triode connected
at Vb=12V
1.5mA with Rag=10MΩ, 2.5mA with Rag=1.5MΩ