Some of the geiger counter kits from Electronics Goldmine use a chain of NE-2 bulbs as their HV DC regulator.
"NE-2 bulbs with resistors"
Cut off the resistors, just use a chain of neon lamps alone.
Wouldn't that change the ionization somehow and thus the intrinsic voltage drop needed to regulate voltage ?
And I say just use one and use resistors like they did in the earlier solid state analog "pass transistor" type regulator controllers.
Agreed, in fact I just posted something to that effect almost.
No. The radiation only lowers the threshold voltage by ionizing some of the gas inside the bulb. It has the same effect as shining a light on the NE-2 to produce the "dark effect". Once the lamp "fires", the lamp is full of ionized gas, which keeps the neon lamp turned on (hysteresis). Once "fired", the operating voltage remains constant and is unaffected by the radiation. Therefore, no change in regulation voltage.
Supposedly, you can use the neon lamp threshold effect to build a gamma ray radiation detector without the GM tube or PIN diode detector (alpha and beta won't go through the thick NE-2 glass envelope): Of course, there are those in this newsgroups who claim it doesn't work:
If you don't like high voltage, there are also PIN diode and solar cell radiation detectors: Or, you can buy one ready to play for your Android or iThing: A friend bought one and we compared it to my CD-700 GM counter. It worked and would detect my sources, but at far lower cpm (counts per min). Actually, the sensitivity is about the same, but the capture area of the PIN diode is much smaller than the GM tube.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
On Sun, 9 Aug 2015 04:49:03 +0000 (UTC), "Geoffrey S. Mendelson" wrote: (...)
Never mind using neon bulbs as regulators. Use zener diodes.
400V High Voltage Regulator. $7.50-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I bet that website is on the watch list :)
Jamie
Back in the day, Tektronix used neons as power indicators. They subsequently banned them from this service as all too often their negative dynamic resistance oscillated with the stray wiring capacitance (as in Jeff L's example). This could get into other parts of the 'scopes and cause real mischief.
The principle of a Geiger detector is that it stores VERY LITTLE energy, and the HV supply isn't regulated, it takes a drastic drop every time a particle is detected, Use a transformer-winding ratio and battery supply at (nearly constant) voltage will give you a steady-enough HV source.
Yep. I have two Tektronix T922 scopes. They're the one's on the top of the pile: "T922Rs below serial number B011950 have a neon power indicator pilot lamp, and those with serial number B011950 and up have an LED power indicator."
Both of mine came with the a neon indicator, which could sometimes be visually seen oscillating at about 2 Hz. There is a 1uf across the neon lamp and 100K resistor in series. It's powered by +100v unregulated, which should be high enough to prevent oscillation, but doesn't. Per a suggestion on the Yahoo TekScopes group, I replaced it with an LED. The 2 Hz glitches on the slow sweeps went away.
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
I don't have a watch list. I keep a collection of bookmarks on CDV-700 repairs because I was receiving about one related repair question per month. The short story is that I own exactly one CDV-700
6B Lionel GM Survey Meter: Thanks to my inept initial repairs, I had some difficulties getting it to work reliably. I compounded my mistake by allowing the two D cell batteries to leak all over the inside. After a few assorted questions and answers in various Yahoo groups, I managed to fix it. Since then, I've repaired 5 similar meters, mostly by careful cleaning the phenolic PCB. Two had sick GV3A Corotron regulator tubes, which I replaced with a string of zener diodes totaling 900v. I also replace the nearby high voltage disc capacitors which ocassionally arc over and short.Would you believe only 2 transistors?
-- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558
That was one of the tricks that Victoreen did for their Corotron(TM) high voltage regulators.
Perhaps you are confusing the striking voltage with the on/regulating voltage (different ionization levels,look in Handbook of Chemistry and Physics).
Their solid-state HV regulator is a lot noisier than the Codatron(R), roughly as bad as the regulators that Titan Industries used to make.
Something I never had cause to look into, but if that voltage really is that stable I guess that is sort of the tube equivalent of a Zener diode, bidirectional in fact.
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