This is really helpful! My High School has a bunch of old Civil Defense boxes full of equipment & I got a few items I’m getting more later, but I got a Dosimeter & its charger, so this really helped!
Great information, I’ve had one of these for years, actually keep it with my medicine so it’s always with me but wasn’t sure how to use it was was actually guessing it out the best I could!! Thanks again!!
An excellent, very informative video. Thank you. One correction regarding oscilloscopes. They certainly can have thousands of volts power supplies, but not at 3 to 4 amps. That would make the oscilloscope a multi-kilowatt device, which it is not.
What would you recommend as a replacement transistor if the existing one has failed? The manual lists the part as GE 40-16. Is it a General Electric (GE) part or a Germanium (Ge) transistor. I’d appreciate any insights you could provide. Thanks
Pretty good. But the fiber moves on electrostatic repulsion rather than any piezo or crystal effect. They used quartz but a carbon fiber can be used as in later models.
the charging contact in the pen is a spring loaded contact switch. it also activates when you are pushing down. if you cant get the pen to take a charge take a plastic pen and push on the contact for a few time then retry
Just got 3 of these pens (2 v-740s and 1 v-730) and a charger but i am unable to see the fiber. Is it possible that it shattered, there is a fair bit of particals on the lenses. Any help would be amazing!
Most likely it has drifted off scale. Press firmly like your charging it and try to adjust the knob clockwise and counter clockwise. The fiber should return within range of the scale. It might take a couple of tries. Good luck.
I work in a local museum and was interested in acquiring one of these pencil dosimeters in the original plastic bag with the packaging to exhibit with our area's other Civil Defense memorabelia. I would be inclined to believe that they are safe to own (particularly if they have never been used), but does anyone know if there is any harmful elements within one of these? I know proper contemporary geiger counters have a radialogical source inside them.
Have a 750 on the way in the mail to me, with some of the 754 pens, as well as a much rarer CD V-138 pen that has a range of 0-200 milliroentgen for training.
You can't really fix them, I have saved some in a vacuum chamber but usually doesn't work. Since you know how much it loses in a day, you could still use it knowing the rate of discharge. That number might get worse over time, so you would have to keep checking it over the years.
Mine has a germanium transistor in it. Can I switch to a silicon transistor without too many changes? I have a 943/2n1101 transistor in my v756 unit. I haven't found any cross reference to a silicon replacement yet.
Try. It's about the only thing that can go wrong in these chargers. You'll not find any direct replacement for a germanium transistor because they'll work down to lower voltage. But as said try. If it doesn't work satishfactory then try a transistor with higher or lower hFE than the one you first tried. That said you should be able to find suitable germanium transistors today. Mine has an OC83 in it. So if you can't find that exact then try another one with roughly similar data - it really doesn't matter that much. What matters most is that it can handle the power and voltage (voltage is not an issue here as the transistor only experiences 1,5v). OC83 can be easily found on ebay.
The transistor in mine is a CK721 which is one of the earliest experimenters transistors, i would try any low level PNP in it. I would try a 2n3905 - because i have a handful of them. The specs look like it will work.
They are only meant to be used for a short period of time, say a day or less. The model CD V742 shown goes to 200R which wouldn't kill you,, but would likely be sick with radiation poisoning. At 450R exposure you would have a 50% chance of death.
You're supposed to wear it clip to the outside of your shirt pocket so that does emitter hangs on the commonly worn on a string or lanyard around your neck. The idea of being is you would keep it close to the center of your chest to give you an idea of overall body absorption.
Oh, boy. You were doing pretty well till you hit 8:30 and then you went off the rails. First your description of equipment from the era shows a complete lack of knowledge. The 220 volts in the dosimeter charger is at a VERY small amperage. It is powered by a 1.5 volt battery. that means this is a 1.5 to 220 volts, a 1 to 145 which means the amperage is miniscule, the CK721 transistor is a germanium that is limited to less than 0.1 amps - above that it smokes. if i divide 0.1 amps by 145 I get 0.0007 amps or 700 microamps. You MIGHT get a shock. Because the oscillator frequency is high - listening to it m it is over 2khz. I would guess that less than .5 Microfarads is enough and that stores nearly nothing. A filter capo needs to store enough during the one half of the cycle to put out enough during the other half. The capacitor will be a low value, not storing much. I own the older model that is point to point wiring. The 900 volts in the Geiger counters is even less dangerous.
Your right on, the equipment isn't particularly dangerous at all however I usually try to avoid liability so saying words like "high voltage" is usually enough to discourage most people unfamiliar with electronics even though the current levels are very very low and the risk of shock is miniscule and might make you say a few choice words at best. If you notice I responded to a few comments years ago regarding electric shock stating the current levels were very low and I wouldn't worry about it. And before you go saying things like lack of understanding, my description of equipment from the era was aimed at equipment from the 20s - 40s, after reviewing it I cant believe I said 50s and 60s. must have had the dates mixed up in my head since most of my electronic equipment is from the second world war.
Okay let me just speed this up for him so that he can stop talking so much about how this thing works it's very simple, you have a DC battery or 1.5 volt battery it drives a small transistor that creates a pulsing Square wave output at Polson Square wave output is then fed to a rectifier diode that rectifier diode then creates a slower Square wave output it is now pulsing DC that pulsing DC is fed through a capacitor that capacitor charges to a peak value and provides your high voltage DC to charge your pendocimeter the general things you have to watch out for the transistor used is made of germanium which is extremely sensitive and absorbs moisture over the last 60 years. I would also suggest not playing with the adjustment for the auto Transformer as it's actually a choke coil used to control the frequency of the oscillator circuit. In the manual it explains that you can replace the transistor with almost any equivalent or general purpose transistor is a state in the book. And only to make a slight adjustment to get the oscillator to function this is basically how your cheap inverters work nowadays, we take DC it runs a circuit that switches it on and off at a high speed we Rectify that pulsing output to create a rough AC signal and then we filter the signal. That's what this device is basically a miniature version of. If you find that pushing down on the switch is a problem. You can put softer Springs in. However make sure they're still enough tension at the switch returns to the full-up position or else the unit will stay running. Cleaning the contact with a Q-tip and rubbing alcohol, for intermittent connections also a Q-tip saturated with alcohol ran around the inside of the bottom of the cimeter pressing fairly hard, to force the Q-tip inside not so hard that you break the device but that you force it up against the lens internally. Originally these were distributed with a plastic cap that went over the end of the decimeter after and back to zero. The cap was installed partially to protect the unit from beta radiation and to keep dust and dirt from accumulating inside the end of the pen. Any trash or spots or Speckles you see when looking through the aperture of the pen. Is most likely on the lens at the bottom. As basically you're looking through a small microscope so even a small spot of dust is going to look quite large. So cleaning the inside of the pen thoroughly and even using some Electronics contact cleaner helps to reduce antioxidation. Because the only contact point is the shell of the pen and the center conductor. In some cases as the manufacturing tolerance is for somewhat wide on these wrap a small amount of foil around the post of the switch on the charger in the Box. It just increases the diameter slightly which makes it a little tighter fit and gives a little better connection. The V 138 is the decimeter that you want to have. That's the one that reads in Miller rankin. All other dosimeters were designed for high level Fallout team use. The ones that run in the 10 Rankin and in some cases 100 rent can you will never see them move with normal background radiation even after weeks. By the time the small fiber moves even off of the zero mark on a 10 rent can scale. The unit will most likely have lost its charge according to the manual for these units a decimeter once charged should stay functional reading background radiation for approximately one month this was in 1956. So again the standards are going to change a little bit as the vacuum inside the dosimeter pen has leaked down. There's only one company in the United States and it's the same one that will calibrate the civil defense Geiger counters will also calibrate your decimeters. It costs around $35 per decimeter to have it ran against a calibrated source and they produce a chart showing you its sensitivity. Frankly these are great toys to keep around for historical purposes but I would never count on one in actual radiological event. The modern digital equivalents are easily found on eBay and are not very expensive. The chances of this device being severely overloaded in a high radiation field. Such as the 200 M rentcon unit if taken into an actual environment that is say five rent can. Would cause the unit overload and you would have absolutely no idea of your exposure level. Hence why they were for training purposes only. Again if you're working with radiation or around it buy a reliable dosimeter. There are several digital models available on the market that are fairly inexpensive. And use a more modern device. I did wear one of these on my shirt when I worked at Lawrence Livermore Laboratories but it was mostly at The Conversation Piece rather than an actual diagnostic device. As there are quite a few that show the engineers at the lab wearing these old style decimeters. So for historical purposes I thought it was funny however I would check it against my film badge however usually the two were never even close to each other. As the film badge was far more sensitive and showed cumulative exposure over A month's time where the dosimeter was recharged daily. Most cases the decimeter display was actually very low due to the heavy shielding in the buildings we were in. And how well we were kept shielded from the radiological sources. Hope that's a better explanation that's a little faster to read.
This is really helpful! My High School has a bunch of old Civil Defense boxes full of equipment & I got a few items I’m getting more later, but I got a Dosimeter & its charger, so this really helped!
Great information, I’ve had one of these for years, actually keep it with my medicine so it’s always with me but wasn’t sure how to use it was was actually guessing it out the best I could!! Thanks again!!
An excellent, very informative video. Thank you.
One correction regarding oscilloscopes. They certainly can have thousands of volts power supplies, but not at 3 to 4 amps. That would make the oscilloscope a multi-kilowatt device, which it is not.
What would you recommend as a replacement transistor if the existing one has failed? The manual lists the part as GE 40-16. Is it a General Electric (GE) part or a Germanium (Ge) transistor. I’d appreciate any insights you could provide. Thanks
Pretty good. But the fiber moves on electrostatic repulsion rather than any piezo or crystal effect. They used quartz but a carbon fiber can be used as in later models.
How do I know what type / rating capacitor and transistor to order?
Thanks! Good educational video
the charging contact in the pen is a spring loaded contact switch. it also activates when you are pushing down. if you cant get the pen to take a charge take a plastic pen and push on the contact for a few time then retry
Just got 3 of these pens (2 v-740s and 1 v-730) and a charger but i am unable to see the fiber. Is it possible that it shattered, there is a fair bit of particals on the lenses. Any help would be amazing!
Most likely it has drifted off scale. Press firmly like your charging it and try to adjust the knob clockwise and counter clockwise. The fiber should return within range of the scale. It might take a couple of tries. Good luck.
Does the cd v-717 have high voltage as well? And do you have to discharge it even to just install a battery?
I work in a local museum and was interested in acquiring one of these pencil dosimeters in the original plastic bag with the packaging to exhibit with our area's other Civil Defense memorabelia. I would be inclined to believe that they are safe to own (particularly if they have never been used), but does anyone know if there is any harmful elements within one of these? I know proper contemporary geiger counters have a radialogical source inside them.
Have a 750 on the way in the mail to me, with some of the 754 pens, as well as a much rarer CD V-138 pen that has a range of 0-200 milliroentgen for training.
Is there anything that can be done for leaky dosimeters? Maybe put them in a dehydrator a while? Mine is losing about 10 roentgens a day.
You can't really fix them, I have saved some in a vacuum chamber but usually doesn't work. Since you know how much it loses in a day, you could still use it knowing the rate of discharge. That number might get worse over time, so you would have to keep checking it over the years.
Mine has a germanium transistor in it. Can I switch to a silicon transistor without too many changes? I have a 943/2n1101 transistor in my v756 unit. I haven't found any cross reference to a silicon replacement yet.
Try. It's about the only thing that can go wrong in these chargers. You'll not find any direct replacement for a germanium transistor because they'll work down to lower voltage. But as said try. If it doesn't work satishfactory then try a transistor with higher or lower hFE than the one you first tried. That said you should be able to find suitable germanium transistors today. Mine has an OC83 in it. So if you can't find that exact then try another one with roughly similar data - it really doesn't matter that much. What matters most is that it can handle the power and voltage (voltage is not an issue here as the transistor only experiences 1,5v). OC83 can be easily found on ebay.
The transistor in mine is a CK721 which is one of the earliest experimenters transistors, i would try any low level PNP in it. I would try a 2n3905 - because i have a handful of them. The specs look like it will work.
How much the charge will laston the diosemeter meter.
And whats the safe range
Ratogens??
Sorry for my bad english
They are only meant to be used for a short period of time, say a day or less. The model CD V742 shown goes to 200R which wouldn't kill you,, but would likely be sick with radiation poisoning. At 450R exposure you would have a 50% chance of death.
Do you know what voltage the lamp runs on if it needs replaced?
It's a 1.3Volt 0.1Amp #131 screw type flashlight bulb. You should never have to change it, but if it goes bad he showed you the spare bulb inside.
@@ForbiddTV i believe in being prepared. My spare was missing on mine. Thanks for the info on the bulb.
I have the same device but have not used it yet, was a little worried about receiving a shock from it. ☺
I wouldn't worry about it, the hv is well contained and this device operates at low current.
@@highvoltagemayhem3345 I have a bad ticker so I'm usually a little more cautious, thanks! 😊👍🏻
So do wear it in a shirt pocket?
You're supposed to wear it clip to the outside of your shirt pocket so that does emitter hangs on the commonly worn on a string or lanyard around your neck. The idea of being is you would keep it close to the center of your chest to give you an idea of overall body absorption.
How do I remove the spare bulb
It's real tight in there. Try unscrewing it while pushing from up from the bottom with something like a butter knife.
Oh, boy. You were doing pretty well till you hit 8:30 and then you went off the rails. First your description of equipment from the era shows a complete lack of knowledge. The 220 volts in the dosimeter charger is at a VERY small amperage. It is powered by a 1.5 volt battery. that means this is a 1.5 to 220 volts, a 1 to 145 which means the amperage is miniscule, the CK721 transistor is a germanium that is limited to less than 0.1 amps - above that it smokes. if i divide 0.1 amps by 145 I get 0.0007 amps or 700 microamps. You MIGHT get a shock. Because the oscillator frequency is high - listening to it m it is over 2khz. I would guess that less than .5 Microfarads is enough and that stores nearly nothing. A filter capo needs to store enough during the one half of the cycle to put out enough during the other half. The capacitor will be a low value, not storing much. I own the older model that is point to point wiring. The 900 volts in the Geiger counters is even less dangerous.
Your right on, the equipment isn't particularly dangerous at all however I usually try to avoid liability so saying words like "high voltage" is usually enough to discourage most people unfamiliar with electronics even though the current levels are very very low and the risk of shock is miniscule and might make you say a few choice words at best. If you notice I responded to a few comments years ago regarding electric shock stating the current levels were very low and I wouldn't worry about it. And before you go saying things like lack of understanding, my description of equipment from the era was aimed at equipment from the 20s - 40s, after reviewing it I cant believe I said 50s and 60s. must have had the dates mixed up in my head since most of my electronic equipment is from the second world war.
Okay let me just speed this up for him so that he can stop talking so much about how this thing works it's very simple, you have a DC battery or 1.5 volt battery it drives a small transistor that creates a pulsing Square wave output at Polson Square wave output is then fed to a rectifier diode that rectifier diode then creates a slower Square wave output it is now pulsing DC that pulsing DC is fed through a capacitor that capacitor charges to a peak value and provides your high voltage DC to charge your pendocimeter the general things you have to watch out for the transistor used is made of germanium which is extremely sensitive and absorbs moisture over the last 60 years. I would also suggest not playing with the adjustment for the auto Transformer as it's actually a choke coil used to control the frequency of the oscillator circuit. In the manual it explains that you can replace the transistor with almost any equivalent or general purpose transistor is a state in the book. And only to make a slight adjustment to get the oscillator to function this is basically how your cheap inverters work nowadays, we take DC it runs a circuit that switches it on and off at a high speed we Rectify that pulsing output to create a rough AC signal and then we filter the signal. That's what this device is basically a miniature version of. If you find that pushing down on the switch is a problem. You can put softer Springs in. However make sure they're still enough tension at the switch returns to the full-up position or else the unit will stay running. Cleaning the contact with a Q-tip and rubbing alcohol, for intermittent connections also a Q-tip saturated with alcohol ran around the inside of the bottom of the cimeter pressing fairly hard, to force the Q-tip inside not so hard that you break the device but that you force it up against the lens internally. Originally these were distributed with a plastic cap that went over the end of the decimeter after and back to zero. The cap was installed partially to protect the unit from beta radiation and to keep dust and dirt from accumulating inside the end of the pen. Any trash or spots or Speckles you see when looking through the aperture of the pen. Is most likely on the lens at the bottom. As basically you're looking through a small microscope so even a small spot of dust is going to look quite large. So cleaning the inside of the pen thoroughly and even using some Electronics contact cleaner helps to reduce antioxidation. Because the only contact point is the shell of the pen and the center conductor. In some cases as the manufacturing tolerance is for somewhat wide on these wrap a small amount of foil around the post of the switch on the charger in the Box. It just increases the diameter slightly which makes it a little tighter fit and gives a little better connection. The V 138 is the decimeter that you want to have. That's the one that reads in Miller rankin. All other dosimeters were designed for high level Fallout team use. The ones that run in the 10 Rankin and in some cases 100 rent can you will never see them move with normal background radiation even after weeks. By the time the small fiber moves even off of the zero mark on a 10 rent can scale. The unit will most likely have lost its charge according to the manual for these units a decimeter once charged should stay functional reading background radiation for approximately one month this was in 1956. So again the standards are going to change a little bit as the vacuum inside the dosimeter pen has leaked down. There's only one company in the United States and it's the same one that will calibrate the civil defense Geiger counters will also calibrate your decimeters. It costs around $35 per decimeter to have it ran against a calibrated source and they produce a chart showing you its sensitivity. Frankly these are great toys to keep around for historical purposes but I would never count on one in actual radiological event. The modern digital equivalents are easily found on eBay and are not very expensive. The chances of this device being severely overloaded in a high radiation field. Such as the 200 M rentcon unit if taken into an actual environment that is say five rent can. Would cause the unit overload and you would have absolutely no idea of your exposure level. Hence why they were for training purposes only. Again if you're working with radiation or around it buy a reliable dosimeter. There are several digital models available on the market that are fairly inexpensive. And use a more modern device. I did wear one of these on my shirt when I worked at Lawrence Livermore Laboratories but it was mostly at The Conversation Piece rather than an actual diagnostic device. As there are quite a few that show the engineers at the lab wearing these old style decimeters. So for historical purposes I thought it was funny however I would check it against my film badge however usually the two were never even close to each other. As the film badge was far more sensitive and showed cumulative exposure over A month's time where the dosimeter was recharged daily. Most cases the decimeter display was actually very low due to the heavy shielding in the buildings we were in. And how well we were kept shielded from the radiological sources. Hope that's a better explanation that's a little faster to read.
Variable "transformer" - no, potentiometer. A variable resistor.
Arkie Shibley is that you?