Photo multipliers are extremely sensitive , a gen3 nvd tube might only be
40k-60k X light gain.
You can tell if the crystal is still good if it is clear, if it is dark and
discolored its bad.
/watch?v=kRVpm6JPibw
They will only light up enough to see it with the naked eye with a xray
source, and even with this it is much lower light output than a xray
intensifying screen.
I looked up the data for the 931A photomultiplier used in the 1077 and it’s
response dies around 670nm. Infrared starts at about 700nm so I think the
B&K just can’t “see” the remote controls output.
I think you confused IR and UV around, remotes use IR, not UV. (that looked
like a DirectTV remote, which if I recall can also do RF, but that doesn’t
matter here) As for the 60hz strobing LED picking up on that odd test rig
(interesting, I don’t think I caught what that was, and have no idea what
that would even be for)… I suspect that the photomultiplier tube is
either A) overwhelmed by the light, or the LED bulb is causing
interference. – I don’t recall if you mentioned if the scintillation
detector was working before you started taking it apart or not. As for the
crystal, I do recall someone doing a video on them, (here is one of them: a
close look INTO a scintillation crystal (radiation detector) / sodium
iodide + thallium / NaI(Tl)). Also while looking I found a really good
video comparing scintillators and Geiger counters (Geiger Counter vs.
Scintillator )
Hello, Well i should say ive watched all your vids. Just never said so
until now. But i do want to say, i was at my local supermarket a week or so
back and picked up out of the box some Tangelos, or Mandarins, one of the
2, i like them, easy to peal and nice taste, I looked again and it said
product of japan. First thought Fukushima. Next thought Tepco lies. LOL i
put them straight back and thought what a shame. I would never now want
anything from Japan. Nice old Geiger counter you have, fix it so i can loan
it aye, The supermarket trolleys are big enough to handle your old school
counter 🙂
Ps like ya underground vids the most
I, for one, am glad that Shango has decided to repair his safety equipment.
Once he has it operational, hopefully he’ll be able to adjust and calibrate
it to manufacturer’s specifications and use it as a safety monitor when
repairing/restoring vintage tube-chassis color television sets. When
working on these sets, one never knows how much X-radiation one is being
exposed to. It would be interesting to see it in action at the beach in
monitoring radioactive water currents/plutonium particles from Fukushima.
Folks might already know this, but that bit of radioactive material under
the tape on the side of the housing of the scintillation counter is there
so one can test to see if it’s working; just hold the probe up to it.
Growing up during the Cold War, these things were pretty commonplace back
then.
Hi Shango, I enjoy your site. When those crystals get yellow they are no
good. The yellowing is caused the the oxidation of the Na. Once you have a
scintillator tube open you have to let it sit for 8 hours or so until all
of the photons escape or else the detector will show a high background.
Those radiation levels I saw the guy in CA reading were really very small,
it takes 3300cpm to equal 1mR in many GM tubes.
Was the PMT getting any high voltage from the oremaster? Unplug the PMT and
check between pins 12 and 7 for about 1kv. You’ll need a very very high
impedance meter since the current is so small. The CRT hv meter should
work. Once you have high voltage, throw the bad crystal away and get one of
the plastic crystals on ebay. The plastic ones don’t absorb water and go
bad.
I all too often realize that I shouldn’t have taken something apart. But
haven’t we all.. Lol
Photo multipliers are extremely sensitive , a gen3 nvd tube might only be
40k-60k X light gain.
You can tell if the crystal is still good if it is clear, if it is dark and
discolored its bad.
/watch?v=kRVpm6JPibw
They will only light up enough to see it with the naked eye with a xray
source, and even with this it is much lower light output than a xray
intensifying screen.
I looked up the data for the 931A photomultiplier used in the 1077 and it’s
response dies around 670nm. Infrared starts at about 700nm so I think the
B&K just can’t “see” the remote controls output.
I think you confused IR and UV around, remotes use IR, not UV. (that looked
like a DirectTV remote, which if I recall can also do RF, but that doesn’t
matter here) As for the 60hz strobing LED picking up on that odd test rig
(interesting, I don’t think I caught what that was, and have no idea what
that would even be for)… I suspect that the photomultiplier tube is
either A) overwhelmed by the light, or the LED bulb is causing
interference. – I don’t recall if you mentioned if the scintillation
detector was working before you started taking it apart or not. As for the
crystal, I do recall someone doing a video on them, (here is one of them: a
close look INTO a scintillation crystal (radiation detector) / sodium
iodide + thallium / NaI(Tl)). Also while looking I found a really good
video comparing scintillators and Geiger counters (Geiger Counter vs.
Scintillator )
Nice bit of kit!!!!
Hello, Well i should say ive watched all your vids. Just never said so
until now. But i do want to say, i was at my local supermarket a week or so
back and picked up out of the box some Tangelos, or Mandarins, one of the
2, i like them, easy to peal and nice taste, I looked again and it said
product of japan. First thought Fukushima. Next thought Tepco lies. LOL i
put them straight back and thought what a shame. I would never now want
anything from Japan. Nice old Geiger counter you have, fix it so i can loan
it aye, The supermarket trolleys are big enough to handle your old school
counter 🙂
Ps like ya underground vids the most
Very interesting stuff you got there.
I, for one, am glad that Shango has decided to repair his safety equipment.
Once he has it operational, hopefully he’ll be able to adjust and calibrate
it to manufacturer’s specifications and use it as a safety monitor when
repairing/restoring vintage tube-chassis color television sets. When
working on these sets, one never knows how much X-radiation one is being
exposed to. It would be interesting to see it in action at the beach in
monitoring radioactive water currents/plutonium particles from Fukushima.
Folks might already know this, but that bit of radioactive material under
the tape on the side of the housing of the scintillation counter is there
so one can test to see if it’s working; just hold the probe up to it.
Growing up during the Cold War, these things were pretty commonplace back
then.
Interesting device.
Hi Shango, I enjoy your site. When those crystals get yellow they are no
good. The yellowing is caused the the oxidation of the Na. Once you have a
scintillator tube open you have to let it sit for 8 hours or so until all
of the photons escape or else the detector will show a high background.
Those radiation levels I saw the guy in CA reading were really very small,
it takes 3300cpm to equal 1mR in many GM tubes.
Was the PMT getting any high voltage from the oremaster? Unplug the PMT and
check between pins 12 and 7 for about 1kv. You’ll need a very very high
impedance meter since the current is so small. The CRT hv meter should
work. Once you have high voltage, throw the bad crystal away and get one of
the plastic crystals on ebay. The plastic ones don’t absorb water and go
bad.
Infrared is one thing and ultraviolet is other thing. The wavelenght is
different.
You murdered the photomultiplier the second you turned it on with ambient
light around.