Detectron Geiger Counter

[David Nebenzahl]

On 4/24/2010 1:02 AM N_Cook spake thus:

Jeff Liebermann <jeffl@cruzio.com> wrote in message
news:kcf4t5hlkdkjj4h04vns4qf7t8d3dhcsob@4ax.com...

On Fri, 23 Apr 2010 10:38:23 -0700, "Chris F." <zappyman@hotmail.com
wrote:

Schematic of the DG-9 model:
http://www.curtcass.com/detectron/dg9-sch.jpg
Probably quite similar to the DG-7.

I'll stand on my comments that your clip lead and external power
supply kludge is probably causing problems. Find some suitable
electrolytics and place them across where the battery would normally
connect. The idea is to reduce the impedance that the counter sees in
the direction of the power supplies. That should reduce the
motorboating (oscillation).

Does USA "kludge" = UK "bodge" ?

Yes, except that I'm going to insist that the proper spelling is
"kluge"[1], which rhymes with "luge", not kludge which would rhyme with
fudge (which would just be wrong!).


[1] I'm fairly certain, though I can't prove it, that this term comes
from a line of printing equipment made by the company called Kluge,
which included a number of very complex Rube-Goldbergian machines, hence
the current usage.


--
The fashion in killing has an insouciant, flirty style this spring,
with the flaunting of well-defined muscle, wrapped in flags.

- Comment from an article on Antiwar.com (http://antiwar.com)

 

[PeterD]

On Sat, 24 Apr 2010 07:51:13 -0700, "Chris F." <zappyman@hotmail.com>
wrote:

I'll stand on my comments that your clip lead and external power
supply kludge is probably causing problems. Find some suitable
electrolytics and place them across where the battery would normally
connect. The idea is to reduce the impedance that the counter sees in
the direction of the power supplies. That should reduce the
motorboating (oscillation).

I tried putting a 100uF cap in that area, the result was that it greatly
increased the frequency of the stray clicks....
I wonder if a row of 10 9-volt batteries would work?

Probably would, but may not for very long. Why not an inverter with an
output of about 90 VDC? The current is not very great, you could
probalby bodge one together easily enough.

 

[Jeff Liebermann]

On Sat, 24 Apr 2010 10:45:48 -0700, "Chris F." <zappyman@hotmail.com>
wrote:

Did you figure out where the yellow electrolytic in the photo was
connected? Power supply filter or meter integrator?

It's connected across the meter.

Ok, ignore it. I was hopeing for power supply.

Find an oscilloscope that can tolerate some high voltage (i.e. 100x
probe). Look at the power supply line. Got pulses? If so, get rid
of them with a filter cap.

Already tried that.... or are you talking about the AC line feeding my
transformer/rectifier/cap power supply?

No. I meant high voltage battery positive lead. If there's
motorboating there, then the power supply may need to be filtered.

If that shows nothing useful, follow the signal path from the GM tube
(after the coupling capacitor so that you're not looking at 900VDC) to
the first grid, to that tube's plate, to the next grid, and so on. You
should be able to see the motorboating.

I might do that. Can't think of anything else it might be, as it's really a
rather basic circuit.

Then, trace it out. From the photo, it looks simple enough.

BTW that small tube with the 2 leads I mentioned is a
5841 (voltage regulator), and I don't have a sub for it.

It's a 900VDC regulator. Same as Victoreen GV3A-900.
<http://www.logwell.com/tech/app_notes/VictoreenCatalog.pdf>
See if there's any oscillations cross the tube with a high-voltage
probe. It could be acting as a relaxation oscillator (as in a
neon-lamp oscillator). Solid state replacement:
<http://www.logwell.com/products/Codatron_Corotron.html>

More for the collection (but nothing useful):
<http://www.orau.org/ptp/collection/surveymeters/Detectrondg7.htm>
<http://www.nukeworker.com/pictures/displayimage-442-47.html>
<http://www.orau.org/ptp/collection/surveymeters/Detectrondg2.htm>
<http://www.dvq.com/geiger/detdg7.jpg>
<http://www.vex.net/~flint/geigerboy/page3.htm>

Here's an eBay listing that has expired.
<http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270535217184>

--
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

 

[Jeff Liebermann]

On Fri, 23 Apr 2010 16:00:06 +0100, "N_Cook" <diverse@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.

--
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

 

[Ian Jackson]

In message <7f86t556ufr4kvg5kr9fsv8tk5gavleadd@4ax.com>, Jeff Liebermann
<jeffl@cruzio.com> writes

On Sat, 24 Apr 2010 09:02:32 +0100, "N_Cook" <diverse@tcp.co.uk
wrote:

Does USA "kludge" = UK "bodge" ?

I think so. Also sometimes spelled kluge.
http://en.wikipedia.org/wiki/Kludge

Be aware that, while "bodge" and "botch" tend to get used

interchangeably, "bodging" and "botching" are not the same thing.

A "bodger" is a skilled, itinerant wood worker.
http://en.wikipedia.org/wiki/Bodging

A "botcher" is someone who fakes doing a proper job of something.

If a kludge provides a functionally adequate (but inelegant) solution,
I'm not sure whether it is really a bodge or a botch.
--
Ian

 

[Chris F.]

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. I'm going to take a break from this for a while, and then try
building a better power supply, and I will post back with the results.
There was something of interest in those links you posted; one specified a
15-volt C battery (for the tube bias) - I was only using about 4.5V. Don't
know if that would have much effect on things, but it's worth a try.
Thanks for the advice.


"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:6a37t5hbf22hf1dum9vs77e80hc8p80a33@4ax.com...

On Sat, 24 Apr 2010 10:45:48 -0700, "Chris F." <zappyman@hotmail.com
wrote:

Did you figure out where the yellow electrolytic in the photo was
connected? Power supply filter or meter integrator?

It's connected across the meter.

Ok, ignore it. I was hopeing for power supply.

Find an oscilloscope that can tolerate some high voltage (i.e. 100x
probe). Look at the power supply line. Got pulses? If so, get rid
of them with a filter cap.

Already tried that.... or are you talking about the AC line feeding my
transformer/rectifier/cap power supply?

No. I meant high voltage battery positive lead. If there's
motorboating there, then the power supply may need to be filtered.

If that shows nothing useful, follow the signal path from the GM tube
(after the coupling capacitor so that you're not looking at 900VDC) to
the first grid, to that tube's plate, to the next grid, and so on. You
should be able to see the motorboating.

I might do that. Can't think of anything else it might be, as it's really
a
rather basic circuit.

Then, trace it out. From the photo, it looks simple enough.

BTW that small tube with the 2 leads I mentioned is a
5841 (voltage regulator), and I don't have a sub for it.

It's a 900VDC regulator. Same as Victoreen GV3A-900.
http://www.logwell.com/tech/app_notes/VictoreenCatalog.pdf
See if there's any oscillations cross the tube with a high-voltage
probe. It could be acting as a relaxation oscillator (as in a
neon-lamp oscillator). Solid state replacement:
http://www.logwell.com/products/Codatron_Corotron.html

More for the collection (but nothing useful):
http://www.orau.org/ptp/collection/surveymeters/Detectrondg7.htm
http://www.nukeworker.com/pictures/displayimage-442-47.html
http://www.orau.org/ptp/collection/surveymeters/Detectrondg2.htm
http://www.dvq.com/geiger/detdg7.jpg
http://www.vex.net/~flint/geigerboy/page3.htm

Here's an eBay listing that has expired.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=270535217184

--
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

 

[Jeff Liebermann]

On Sun, 25 Apr 2010 08:53:38 +0100, Ian Jackson
<ianREMOVETHISjackson@g3ohx.demon.co.uk> wrote:

In message <7f86t556ufr4kvg5kr9fsv8tk5gavleadd@4ax.com>, Jeff Liebermann
jeffl@cruzio.com> writes
On Sat, 24 Apr 2010 09:02:32 +0100, "N_Cook" <diverse@tcp.co.uk
wrote:

Does USA "kludge" = UK "bodge" ?

I think so. Also sometimes spelled kluge.
http://en.wikipedia.org/wiki/Kludge

Be aware that, while "bodge" and "botch" tend to get used
interchangeably, "bodging" and "botching" are not the same thing.

A "bodger" is a skilled, itinerant wood worker.
http://en.wikipedia.org/wiki/Bodging

A "botcher" is someone who fakes doing a proper job of something.

If a kludge provides a functionally adequate (but inelegant) solution,
I'm not sure whether it is really a bodge or a botch.

Ok, I'm lost in the translation. However, it's good to know that the
Kings English has multiple names for what I do naturally when
confronted with a technical problem. Such multiple names are a sign
of sophistication and tends to identify what a society considers
important. For example, the Eskimo's have multiple names for
different types of snow. In Yiddish, we have multiple names for the
different types of "idiot". In government, there are multiple names
for the different types of taxation.

I'm sure something profound can be extracted from all this, but I
don't want to ruin a nice weekend by attempting to think.


--
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

 

[Baron]

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.

 

[Baron]

Jeff Liebermann Inscribed thus:

On Fri, 23 Apr 2010 16:00:06 +0100, "N_Cook" <diverse@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.

 

[Chris F.]

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@linuxmaniac.nospam.net> wrote in message
news:hr1pta$uog$1@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.

 

[Chris F.]

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".

 

[Baron]

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.

 

[tm]

Did you read the information in this link? Scroll down to the
discussion on the regulator tube.

http://www.dvq.com/geiger/heath_rc1.pdf

The 900 volt regulator tube operates in three regions; corona,
glow, and arc. It is sensitive to the high voltage supply conditions,
i.e. ripple can cause it to oscillate between the modes. Also, it is
sensitive to the filter capacitance.

 

[Jeff Liebermann]

On Sun, 25 Apr 2010 17:28:31 +0100, Baron
<baron.nospam@linuxmaniac.nospam.net> wrote:

Hey Jeff,

You rang?

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 ?

Tubes are what you roll the toilet paper upon. Valves are what
controls the flushing. What more do you need to know?

They are stored in a box somewhere. If I can find them I'll come back
with the CV numbers.

My guess(tm) is a gas filled thyratron or regulator
tube/valve/whatever, where the gas is slightly radioactive to decrease
the ionization voltage. The cathodes were also made with thorium:
<http://www.angelfire.com/electronic/cwillis/rad/tubes.html>
<http://www.tubecollector.org/documents/radioactive.htm>
The 5841 voltage regulator is one of those that is filled with some
radioactive gas. The differences between the various versions, which
breakdown at different voltages, is the amount and type of radioactive
gas or material.


--
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

 

[Chris F.]

I finally got this working, at least to the point where it's now usable. The
trick was to filter the B+ supply between the three tubes, with a
filter+inductor+filter combination, to prevent stray oscillation. It still
generates about 1 stray pulse every 5 seconds or so (not counting normal
background readings), but this may straighten out with some tweaking. Even
if not, the detector is now suitable for measuring above-background levels
of radiation, up to about 20 mr/hr. Should come in handy if the nearby
nuclear power plant ever blows....
Thanks to all for the advice.
"Chris F." <zappyman@hotmail.com> wrote in message
news:4bd08a44$0$12419$9a566e8b@news.aliant.net...

I recently bought an old Detectron model DG-7 geiger counter. This is
from the early 50's and has three 1U5 tubes inside. Power requirements are
90 volts for the B+, two "D" cells for the tube filaments, and a 4.5 volt
bias supply.
I went over the unit, replacing a selenium rectifier and testing the
tubes. The unit powers up, but generates a steady stream of pulses on it's
own, even with the probe detached. The frequency of the oscillation varies
with the range selector knob. The probe is working - when brought near a
source (a bunch of vaseline marbles) it will produce extra clicks in
addition to the stray ones generated by the unit.
I've checked all the other components - resistors, capacitors, etc. The
only thing I couldn't check is a very small tube, which looks like a
cold-cathode rectifier of some kind. I've also tried varying the B+ and
bias voltages. And I can't find a schematic, which makes matters worse.
I'm not sure what to do next. Any ideas?

 

[N_Cook]

Chris F. <zappyman@hotmail.com> wrote in message
news:4be34ede$0$12426$9a566e8b@news.aliant.net...

I finally got this working, at least to the point where it's now usable.
The
trick was to filter the B+ supply between the three tubes, with a
filter+inductor+filter combination, to prevent stray oscillation. It still
generates about 1 stray pulse every 5 seconds or so (not counting normal
background readings), but this may straighten out with some tweaking. Even
if not, the detector is now suitable for measuring above-background levels
of radiation, up to about 20 mr/hr. Should come in handy if the nearby
nuclear power plant ever blows....
Thanks to all for the advice.
"Chris F." <zappyman@hotmail.com> wrote in message
news:4bd08a44$0$12419$9a566e8b@news.aliant.net...
I recently bought an old Detectron model DG-7 geiger counter. This is
from the early 50's and has three 1U5 tubes inside. Power requirements
are
90 volts for the B+, two "D" cells for the tube filaments, and a 4.5
volt
bias supply.
I went over the unit, replacing a selenium rectifier and testing the
tubes. The unit powers up, but generates a steady stream of pulses on
it's
own, even with the probe detached. The frequency of the oscillation
varies
with the range selector knob. The probe is working - when brought near a
source (a bunch of vaseline marbles) it will produce extra clicks in
addition to the stray ones generated by the unit.
I've checked all the other components - resistors, capacitors, etc. The
only thing I couldn't check is a very small tube, which looks like a
cold-cathode rectifier of some kind. I've also tried varying the B+ and
bias voltages. And I can't find a schematic, which makes matters worse.
I'm not sure what to do next. Any ideas?

So what have you found for a long-term test source , high enough emitter at
a
repeatable distance, to say give a count at least 5 times more than
background?
I've managed to lose my old broken gas-lighting mantle I had retained for
this purpose

 

[Jeffrey D Angus]

Chris F. wrote:

Should come in handy if the nearby
nuclear power plant ever blows....

Homer Simpson laughing at the "Run for the hills" alert level
on the warning sign at the power plant. "That will never happen."
Lenny asks him if he thought the power plant was safe. "No, if
the plant blows up, there won't be any electricity to power the
sign."

Jeff


--
“Egotism is the anesthetic that dulls the pain of stupidity.”
Frank Leahy, Head coach, Notre Dame 1941-1954

http://www.stay-connect.com