Geiger counter tube

Don't know about Russian ones but generally its due to failure of the bond around the mica or whatever window on the end of the tube.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Geiger counter tubes are usually for X-ray, Gamma or Beta radiation, relatively few will detect Alpha radiation. Those that do have very thin windows at the ionization chamber such that the large Alpha particle (Helium nucleus) can pass through it and be detected. Such GM tubes are delicate and usually supplied with little covers for when Alpha detection is not required and so as to protect the mica window. Most tubes are filled with a mix of inert gas and a halogen gas... the latter can sometimes attack the seal around the mica. So, if your GM tube has a mica window, that would be the typical failure mode. If not, the wire-lead seals sometimes fail.

Some basic information here.

Peter Wieck Wyncote, PA

Can you elaborate? Can it be fixed?

Thanks. I don't think this one has a mica window. I'll check. The circuit board has had wax poured on it (by the maker, for insulation).

When you say "the wire-lead seals sometimes fail" do you mean they let air leak into the tube, or they fail in some other way that might be fixable?

You cannot fix a GM tube that has failed.

Peter Wieck Wyncote, PA

Right, I couldn't quite tell what was being described was a failure of the tube or of the external circuitry.

I'll check and see if the tube has high voltage across it (apparently not) and then if high voltage develops with the tube disconnected.

Anything can be fixed with the right equipment and enough effort, but from a practical standpoint, no. Once the tube is gassy, it's shot.

Bear in mind that the typical Geiger tube power supply has a very high output impedance, and may be loaded down excessively by most common types of multimeters. If you want an accurate voltage measurement, you will need something like an electrostatic voltmeter.

Bob Weiss N2IXK