Detectron Geiger Counter
in [Repair]
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From: Baron on 25 Apr 2010 12:17 Chris F. Inscribed thus: > At this point, I think you're right - it's probably issue with the B+ > supply, probably a combination of poor filtering and inadequate output > current. After tracing out the schematic that's about the only > conclusion I can come to. Since you get clicks when the tube is not connected, have you checked the EHT supply. It probably has bad caps in there. Something breaking down as the EHT rises. -- Best Regards: Baron.
From: Baron on 25 Apr 2010 12:28 Jeff Liebermann Inscribed thus: > On Fri, 23 Apr 2010 16:00:06 +0100, "N_Cook" <diverse(a)tcp.co.uk> > wrote: > >>Now there is no thorium loaded gas mantles around these days > > Ummm... check out the gas and kerosene mantles from China. Some are > hot: > <http://www.tradevv.com/chinasuppliers/yansong_p_4e599/china-Gas-mantle.html> > Incidentally, I once sacrificed one of my radioactive thorium Coleman > lantern mantles and ran a side by side comparison of the brightness > with a current non-radioactive zirconium mantle. The radioactive > mantle was MUCH brighter. > >>nor radium >>dials , what is commonly around to give an above background check that >>they are working ? > > I like to use KCL (potassium salt, lite salt, or low-sodium salt). The > Potassium 40 is radioactive (450pCi/gram): > <http://802.11junk.com/jeffl/crud/salt.jpg> > <http://www.angelfire.com/electronic/cwillis/rad/nosalt.html> > It's not very hot but works well enough with a GM tube. Also lots of > fun going to the market with my 1950's GM counter. I once found some > brand of sea salt that was really hot, but it had been withdrawn or > recalled before I could return to buy some. > > While at the market, try brazil nuts, acorns, and bananas. K-40 but > only when grown with massive overkill doses of fertilizer. Also try > cat litter. They all show up hot with my scintillation counter, but > are very weak with the GM tube. > > If you go to the hardware store, check out the high phosphate > fertilizer. The stuff has uranium, K-40, thorium, radium, and who > know what else in it. > > While at the hardware store, see if they have any tungsten stick arc > electrodes. They have some Thorium mixed in. > > At home, if you have a dark colored granite counter top, you'll find > it somewhat radioactive from uranium. > <http://greenbuildingelements.com/2009/03/27/granite-showrooms-continue-selling-radioactive-granite/> > The problem isn't so much the radiation. It's the radon gas that it > produces. > > Got any pottery or kitchen plates with a yellow or bright orange glaze > (Fiestaware)? If so, they're uranium oxide. > > Got any old cameras or eyeglasses made between WWII and about 1980? > Most lenses have thorium mixed into the glass to increase the index of > refraction. These are really weak and will only show up on my > scintillation counter. > > Got a heavy scotch tape dispenser with a sand-epoxy mix in the base? > The sand has thorium mixed in. > > Got an old static eliminator for removing the static electricity from > old vinyl records? If so, it's quite hot with Polonium. > > More: > <http://www.kronjaeger.com/hv-old/radio/src/index.html> > <http://www.anythingradioactive.com/radsamples.htm> > <http://www.physics.isu.edu/radinf/natural.htm> See section on food. Hey Jeff, I've several old valves (Tubes) that are marked as containing "Radio Active Material" with a "Do not Break Glass" and a yellow sticker on them. CV number marking. Any ideas ? They are stored in a box somewhere. If I can find them I'll come back with the CV numbers. -- Best Regards: Baron.
From: Chris F. on 25 Apr 2010 13:39 Actually, the way this circuit is designed, any ripple or pulses in the DC supply will be picked up and amplified the same way as pulses from the GM tube. I guess it was never designed to operate on an AC power supply, but I'm sure there's some way areound the problem. I've replaced most of the capacitors (all are high voltage ceramics). "Baron" <baron.nospam(a)linuxmaniac.nospam.net> wrote in message news:hr1pta$uog$1(a)news.eternal-september.org... > Chris F. Inscribed thus: > >> At this point, I think you're right - it's probably issue with the B+ >> supply, probably a combination of poor filtering and inadequate output >> current. After tracing out the schematic that's about the only >> conclusion I can come to. > > Since you get clicks when the tube is not connected, have you checked > the EHT supply. It probably has bad caps in there. Something breaking > down as the EHT rises. > > -- > Best Regards: > Baron. >
From: Chris F. on 25 Apr 2010 13:43 > Hey Jeff, > I've several old valves (Tubes) that are marked as containing "Radio > Active Material" with a "Do not Break Glass" and a yellow sticker on > them. CV number marking. Any ideas ? > They are stored in a box somewhere. If I can find them I'll come back > with the CV numbers. > > -- > Best Regards: > Baron. Probably cold-cathode rectifier tubes, equivalent to types like 0A2, 0D3, etc. I have at least one American-made 0A2 that has a radioactive symbol on the box, and the tube itself says "Contains less than 0.03 microcuries of Krypton".
From: Baron on 25 Apr 2010 14:17
Chris F. Inscribed thus: > Actually, the way this circuit is designed, any ripple or pulses in > the DC supply will be picked up and amplified the same way as pulses > from the GM tube. I guess it was never designed to operate on an AC > power supply, but I'm sure there's some way areound the problem. > I've replaced most of the capacitors (all are high voltage ceramics). Sods Law ! It will be the one that you didn't replace. :-) -- Best Regards: Baron. |