arcadecup
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"Stop ohming yokes" rant follow up. Ionizing radiation event research. 161% increase.
This is in follow up to the yoke mismatching concerns rant that I have posted sometime ago.
https://forums.arcade-museum.com/showthread.php?t=392981
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Chad Entringer
05-20-2017
Purpose: To observe and determine radiation event differences on a CRT when the flyback anode high voltage potential exceeds normal operating conditions.
Since literally almost all monitor boards that I see in the amusements industry have its flyback high voltage potential generation factored by the monitor deflection coil (yoke) this is to address the concern of mismatching monitor boards to deflection coils it was not designed around.
Potential causes for excessive high voltage:
Monitor yoke mismatching. Flyback pulsing capacitors. Excessive monitor chassis B+. Incorrect glass tube used.
Charted is ionizing radiation events emitted from a 20" CRT acquired with a MAZUR PRM-9000 Radiation Monitor. The radiation counter has been positioned 1" from the face of the tube in the same spot through all 3 test modifiers.
The first 15 minute segment average CPM at the CRT turned off with 0kv anode voltage potential resulted in and average count of 87.6
This off state would include background radiation and tube elemental natural decay. I suspect there are possible radioactive phosphor isotopes contributing the higher than normal background readings of 29 CPM
The average background radiation activity level reading with the instrument set on an inert wooden counter was 29 CPM
The second 15 minute segment average CPM at the CRT turned on with a sustained 28.5kv anode voltage potential resulted in an average count of 87.933.
There is no detectable CPM difference detected between the CRT being off and turned on with a normal operation of tolerance of 28.5kv. However, I would expect a verified small increase if the same test was done over a long period such as 24 hours. Other instrumentation and methods would be able to demonstrate the subtle change better.
The third 15 minute segment average CPM at the CRT turned on with a sustained 32kv anode voltage potential resulted in an average count of 230.133
Conclusion: A 3.5kv difference anode voltage potential above a normal operating potential of 28.5kv resulted in a 161.7% increase in ionizing radiation event counts over a 15 minute period on the PRM-9000.
Considerations:
A scintillator would be a more interesting in order to calculate the energy levels (gamma spectroscopy) emitted and radiation types (weight) in order to calculate mR/hr. Future lab addition? Or perhaps good dosimeter that would pick up the energy ranges emitted.
An absorbed dose would be based on radiation weight, energy levels, surface area, what part(s) of the body it's zapping.
It is not possible to calculate the uSv/hr dose since my counter is calibrated in relation to a caesium-137 source.
The Food and Drug Administration strictly limits CRT emissions to .5 mR/hr.
No dose of radiation of safe.
[UPDATE 05-23]
Thanks for the all the supporters, challengers, contributors, the interest and the hunger for more knowledge. Question everything!
I will do more research as I mentioned and obtain accurate dose accumulations from CRT x-rays in normal to excessive HV. Whether extra x-rays are kicked off from excessive b+, a faulty flyback, incorrect PP drive pulsing capacitors, or the yoke by itself this is all fascinating and worthwhile to me.
It may very well end up that a couple cigarettes will deposit more of a radiation dose into tissue than a day or twos worth of an x-ray bath from a CRT. Or not. -->http://www.rmeswi.com/36.html (thanks to coinopper for the link on cig rads)
Thank you all.
This is in follow up to the yoke mismatching concerns rant that I have posted sometime ago.
https://forums.arcade-museum.com/showthread.php?t=392981
---------------------------------------------------------------------------------------
Chad Entringer
05-20-2017
Purpose: To observe and determine radiation event differences on a CRT when the flyback anode high voltage potential exceeds normal operating conditions.
Since literally almost all monitor boards that I see in the amusements industry have its flyback high voltage potential generation factored by the monitor deflection coil (yoke) this is to address the concern of mismatching monitor boards to deflection coils it was not designed around.
Potential causes for excessive high voltage:
Monitor yoke mismatching. Flyback pulsing capacitors. Excessive monitor chassis B+. Incorrect glass tube used.
Charted is ionizing radiation events emitted from a 20" CRT acquired with a MAZUR PRM-9000 Radiation Monitor. The radiation counter has been positioned 1" from the face of the tube in the same spot through all 3 test modifiers.
The first 15 minute segment average CPM at the CRT turned off with 0kv anode voltage potential resulted in and average count of 87.6
This off state would include background radiation and tube elemental natural decay. I suspect there are possible radioactive phosphor isotopes contributing the higher than normal background readings of 29 CPM
The average background radiation activity level reading with the instrument set on an inert wooden counter was 29 CPM
The second 15 minute segment average CPM at the CRT turned on with a sustained 28.5kv anode voltage potential resulted in an average count of 87.933.
There is no detectable CPM difference detected between the CRT being off and turned on with a normal operation of tolerance of 28.5kv. However, I would expect a verified small increase if the same test was done over a long period such as 24 hours. Other instrumentation and methods would be able to demonstrate the subtle change better.
The third 15 minute segment average CPM at the CRT turned on with a sustained 32kv anode voltage potential resulted in an average count of 230.133
Conclusion: A 3.5kv difference anode voltage potential above a normal operating potential of 28.5kv resulted in a 161.7% increase in ionizing radiation event counts over a 15 minute period on the PRM-9000.
Considerations:
A scintillator would be a more interesting in order to calculate the energy levels (gamma spectroscopy) emitted and radiation types (weight) in order to calculate mR/hr. Future lab addition? Or perhaps good dosimeter that would pick up the energy ranges emitted.
An absorbed dose would be based on radiation weight, energy levels, surface area, what part(s) of the body it's zapping.
It is not possible to calculate the uSv/hr dose since my counter is calibrated in relation to a caesium-137 source.
The Food and Drug Administration strictly limits CRT emissions to .5 mR/hr.
No dose of radiation of safe.
[UPDATE 05-23]
Thanks for the all the supporters, challengers, contributors, the interest and the hunger for more knowledge. Question everything!
I will do more research as I mentioned and obtain accurate dose accumulations from CRT x-rays in normal to excessive HV. Whether extra x-rays are kicked off from excessive b+, a faulty flyback, incorrect PP drive pulsing capacitors, or the yoke by itself this is all fascinating and worthwhile to me.
It may very well end up that a couple cigarettes will deposit more of a radiation dose into tissue than a day or twos worth of an x-ray bath from a CRT. Or not. -->http://www.rmeswi.com/36.html (thanks to coinopper for the link on cig rads)
Thank you all.
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