I made Geiger counter and it works just fine for 400 v russian tube, i bought adjustable HV Module it gives from 60 to 1200 volts, the issue is: i want to use it with special tube that works 700v, my Geiger circuit becomes crazy ,led and speaker gives loud tones when high voltage is reaching 700 volt , im attaching my circuit,
Please help nuclear physicists student,

 

Hello,

What is the voltage rating of the 47 pF capacitor?
For the 500 Volts circuit a 630 Volts cap would work, but not for the 700 Volts version.
Then I would take a capacitor with a voltage rating of at least 1000 Volts.

Bertus

 

I used ceramic 104

 

Hello,

Ceramic 104 is an 100 nF capacitor.
See this page how to read the value:
https://marvac.com/pages/ceramic-capacitor-codes
The coupling will be to strong.
Also it does not say anything about the voltage rating.

Bertus

 

Hi Bertus
Thank you for your reply
I have SNM -14 neutron detector tube
It works on 700 volt, http://www.vendio.com/stores/Tati_g...o/snm-14-14-snm-42-42-counter-ne/lid=17684997
Any ideas about it , or a circuit that make it work?
Thanks in advance

 

It could be that the cathode is emitting electrons because of the very high field. If you reverse the polarity of the connections to the tube and the wacky noise goes away that's what was causing the problem.

 

Hello,

There are several other schematics of geiger counters on this page:
http://www.techlib.com/science/geiger.html

Bertus