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X-rays on projection CRT

neazoi

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Hi I had given an old CRT-based rear-projection TV, which I dissasembled. But before doing so I opened it and operated it a few times (total 30 minutes or so). Within this time I think I have also removed the lens from the tubes and I operated it for a few minutes. I am not sure, but I think i did so (it was a few weeks ago).

Now I see this video https://youtu.be/mQbXZxLcqtY?t=75
His lenses write the warning about X-rays, but mine did not (Toshiba TV).
Well I did not stick my eyes in there for sure, I think I was at a distance of at least 0.5m or so from the tubes.

Is what I did really bad, Am I dead?!?!!
 

c_mitra

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It is a wise warning and better be safe.

It does produce a small amount of soft x-rays (you can see that the accelerating voltage is around 25kV and the tube is made of thick glass).

Although the electron beam is focused, the produced x-rays are not. They go in all directions and the intensity falls off if you move away.

It is good to use glasses (even if zero power) for such investigations. Also some zinc sulphide screens are there that show x-ray fluorescence. Can be very handy.

It is better to be prepared in advance. But then your old CRT TVs also produce soft x-rays (but you do not sit in front of the TV at 6 inches!!
 

vfone

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X-rays can cause mutations in human DNA and might lead to cancer.
But most probably the quantity per time of X-rays you took from the CRT tube, is hundreds (maybe thousands) times lower than a normal CT scan.
 

c_mitra

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X-rays can cause mutations in human DNA and might lead to cancer.
Sad but true.

It all depends on many factors. In fact too many.

X-rays are weakly absorbed by the human body. The part that is not absorbed has no effect.

Most important mode of absorption is ionization. Lots of ions (ion-pairs) are produced along the path and most of them promptly recombine (and become harmless) and a part of these ions can make some damage.

Within a cell, DNA takes up a small volume. But a cell that falls in the path of ionization of the x-ray most likely dies.

It is also possible that the x-ray hits the DNA and causes mutation but the cell lives. If the cell is not rapidly dividing, the damage to the DNA has no effect.

Most of the time, mutations in some random parts have little biological effect.

Most of the cells are not rapidly dividing but there are exceptions. For example, cells responsible for reproduction (testis and ovary) or mammary glands and stuff like that.

If the x-ray photon hits your gonads, and causes a mutation in some important part of the DNA and you are young and active, you be worried.

Also the energy of the x-ray matters: it determines the degree of ionization along its path within the cell (per unit length).

Summary: do not worry but be careful.
 

neazoi

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Sad but true.
Summary: do not worry but be careful.
Thanks!

I wonder many people in the past decades were in front of CRT screens, I mean close to them (thinking of the computer people). If significant X-ray radiation was escaping by them, we would be all dead.
Many ignored this fact completely. I have seen people even 10-15cm away from the screen for quite a few hours a day.
 

c_mitra

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If significant X-ray radiation was escaping by them, we would be all dead
Cancer can show up only if the cells are rapidly dividing. Most common cancers are of ovaries, prostate, testis, female breast- regions of high cellular activity.

Skin cancers are less common but not rare. We are exposed and skin cells are replenished regularly.

Tumors are another kind - but you are never sure of the cause. They may show up after long time.

I am not trying to say that the risks are small. I am simply saying that enjoy your work but always take care.
 

BradtheRad

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Once upon a time every town had a TV repair shop. Technicians worked on tv's all day long. They were close to the screen, and close to the tubes.

I asked one of them about exposure to rays from a color tv (because b&w was reputedly less harmful). He said reports were over-hyped.

He knew co-workers who'd been in the business for years with no ill effects. I asked if their children were normal, and he said Yes.
 

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