Russian G-M tubes

Any brief search on ebay for Geiger Tubes, will bring up a whole raft of different Russian devices. If you forget to put the word 'tube' you'll get a whole load of shoes...

It seems the Soviets were a bit obsessed with G-M tubes! They can be had in all manner of forms, sizes, and sensitivities! As the photo below (courtesy pocketmagic.net) shows

Soviet G-M tubes

It would seem that the SMB-20 tube (4th and 5th from top) is considered the standard for low rate homebrew counters, and so this will be one of the tubes I will try. I have on order though a huge STS-6 (2nd from top) and a tiny little Alpha capable device, the SI19BG.

SI19BG Alpha window G-M tube

Ive now made the HV generator permanent. Its not a winner in any design elegance awards! I've literally just pulled the components off of the breadboard, and cobbled them together on a bit of Perfboard! Ive made one change - the 10mH choke has been replaced with a 25mH/20mH transformer taken from an old switching supply. Ive wired the windings in parallel, and I'm able to just about get 530V from it now. I don't know how, or even if, using both windings in any way makes much difference. That's something I can investigate later.

HV Generator Board, and HV probe board

 With the 500Ω single turn preset, setting an exact voltage is very tricky. Future builds will have proper 100Ω multiturn presets, but for now I've managed to set this one to near enough 430V, which is the ZP1481s voltage. The SBM-20s I believe run at 400V.

One of my main goals with these circuits, is that it should be reproducible using 'junk-box' parts. Now, I have spent quite a bit on parts for this - but generally this is in bulk, and so building up my 'junk-box' further! The electronics for a simple Geiger counter should, ideally, cost nothing to any constructor with a reasonable stock of common or garden parts. The expense should all go on A) the G-M tube, and B) the case to put it all in!