Old TV x-ray exposure

[Thyratron]

After just posting a thread in the general topics forum on shoe fluoroscopes (which some of you may remember from years ago), it got me thinking: Many of the old TV repair books caution you from getting too close to the front of the screen when the TV is on. Was this just an "old wives' tale" that was proven generally unfounded later on, or did the old sets actually emit more x-radiation than modern sets do? It seems you don't hear that warning too much anymore.

Yes, the older TVs did emit more X radiation. Just stay more than 3 feet from the screen; the air will stop it. It really isn't that dangerous; I've been working on TVs for decades and I'm perfectly normal (it's everyone else who is screwed up).

[Arkay]

When I was growing up (well, to the extent that I ever did... ), my parents always insisted that we stay at least five feet from the TV screen, because it was "dangerous" (the X-ray thing) and "would wreck our eyes". Not sure about the X-ray issue (although if you think about how X-ray tubes work, it is a VERY reasonable possibility that TV tubes could emit some of those frequencies, too), I think they were right about the latter, for sure, judging from how computer screens at close range tire the eyes!

[OvenMaster]

From what I recall, legislation mandated X-ray protection via lead shielding on the picture tubes made after around 1970 or so. Other tubes emitted radiation as well.
http://hps.org/publicinformation/ate/q498.html
http://hps.org/publicinformation/ate/q4212.html
Tom

[Steve McVoy]

Xray radiation is related to anode voltage, so the main risk was from color sets, which use 20-25 kv. The radiation was both from the CRT and the hv shunt regulator tube.

B & W sets, which typically used 10-15 kv, were not an issue.

[old_tv_nut]

The main risk in a non-defective set was to servicemen running the sets with shielding removed and being constantly exposed day in and day out. The main risk in defective sets was from a defective regulator or rectifier tube (can't remember if it was either or both). The defect was a tilting of the internal parts of the tube, which allowed X-rays to be emitted around the metal parts in the bottom of the tube. Which side of the set would be "hot" depended on the mounting of the emitting tube. In some sets, this would be downward, so a kid sitting up close with feet under a consolette would get exposed. The tube problems were discovered and voluntarily reported by the manufacturer in parallel with instituting new QC measures to prevent defective tubes from being manufactured or sold. Even though the problem was fixed immediately as it was discovered, additional tests were added for all TV sets. I recall tests being done when I was at Motorola, but in general, the levels were so low as to be hard to measure. The introduction of solid-state rectifiers along with greater X-ray blocking in CRT glass eliminated the problem for good. (Now, of course, there are questions about CRT disposal because of the high lead content.)

[bgadow]

Xray exposure at the face of the tube didn't seem to be an issue. I have mentioned before about a service manual for an Admiral set that used the 21AXP22 and they warned about soft xrays at the center of the screen, but that the safety glass was enough to stop them. I guess some of the early bw projection sets ran voltages high enough for this to be an issue...I seem to recall a discussion of that some time ago on here. I have heard of figures like 40-80KV in some odd applications.

It would seem a metal cabinet set would be safest to protect from the HV tubes. There is a website out there featuring Xray photographs taken with the aid of, IIRC, a HV regulator. Kinda eerie.

GE was a company that had trouble with a few late 60s color sets going over the limit. They more than made up for it, switching to a lead-encased HV rectifier (3AT2?) and plastering the inside of some models with a big, bright radiation symbol to catch the attention of, I guess, DIY'ers.

I don't think there is much to worry about for us as hobbyists. I don't recall ever hearing about an epidemic of cancer among TV repairmen.

Sorry to resurrect an old thread, but a response posted recently to another thread

Originally Posted by Phil Nelson

With such extremely high voltage, would this critter be emitting X-rays?

Maybe you should invest in a lead apron -- or at least a tinfoil hat :-)

Phil Nelson

caused me to do a lot of thinking recently, on that restoration project. (B&W Projection TV, 5” tube, 40K Anode voltage.)

My question is, do any old vets out there really have any recommendations to share, with respect to X-Ray exposure? I’ve already taken just about every other precaution I can think of, including insulated workbench & workspace, isolation transformer, and a big sign that says “ONE HAND IN THE POCKET AT ALL TIMES” hung on the wall.

Please don’t tell me I also need to get leaded glass goggles and lead lined underwear too, to keep my eyeballs (and other balls) from falling out/off from working on this. I do want to fix this thing up, but I’d prefer not to die trying. :-)

I can deal with High Voltage, I've done that since High School. But X-Rays?

[mr_fixer]

It's kinda funny but i Have 3 old crt projection units, 2 barco, 1 bell and howell, all of these projectors have a thin sheet of lead either around the CRTs or around the the cabinet. I think on your b&w projector there is a lead coating painted black on the rear section of the crt. Logan

[poohsan]

electrons subjected to a voltage potential accelerate. accelerating electrons emit x-rays. are the x-rays generated by a CRT worth worrying about? probably not.

[markthefixer]

Originally Posted by poohsan

electrons subjected to a voltage potential accelerate. accelerating electrons emit x-rays. are the x-rays generated by a CRT worth worrying about? probably not.

It's the deaccelerating electrons we have to worry about...

The Bremsstrahlung effect, a contraction of the German brems for braking, and strahlung for radiation produces the x-rays.

a facinating read:
http://en.wikipedia.org/wiki/X-ray_tube

99 percent of the electron's energy goes towards heating the anode.

The crt glass is thick, and the extra lead mixed in stops it all. The regulator tubes had the thin pure glass envelopes that allowed more out.

Sitting back is/was more about eyestrain....

[Bill Cahill]

Hmmm. Is that why my friends say I have such a glowing personality???
Bill Cahill :lol:

[Bob E.]

Originally Posted by markthefixer

The crt glass is thick, and the extra lead mixed in stops it all. The regulator tubes had the thin pure glass envelopes that allowed more out.

How about a 3DR3 in its nice lead jacket? It has, printed on the side: "X-Ray warning -- This tube in operation may produce harmful radiation unless it is shielded". The lead coating is about 1/8" thick, and there is a removable paper warning that says "Caution: Contains 55% Lead Oxide, Toxic by Ingestion". I'm guessing it is from the tail-end of tube-production years, when we were all getting more paranoid about what television could do to us!

--Bob

[zenith2134]

Almost a year to the day, I found this thread.

Wondering if any news has surfaced on this issue.

IMO, I'd be slightly more concerned about the EMF from the deflection yoke. X-ray emission in a post-70s set are probably very small.

[kx250rider]

I don't think there's any risk from any X-rays from any TV. It's all a bunch of propaganda to facilitate lawsuits against TV manufacturers back then. Everything on Earth and in the universe can cause cancer, according to all collective research. We're all going to die. Some of us will die after a fulfilling, fun, care-free life; others after hiding from everything and living a sheltered, boring, ultra-safe life. Guess which way I'm seeking? Both of my friends who died young recently were vegetarian health nuts, and were scared of every new "health threat" conjured up by the media.

Charles