CurtPalme.com Home Theater Forum

stefuel

AmPro's have a big honkin sheet metal shroud surrounding the tubes bell. What does the Marquee do? It it in the plastic tube covers?

David_Web · Joined: 02 May 2007 Posts: 418 Location: Sweden

Look at this pic from the other thread.
http://img14.imageshack.us/img14/9240/aaaaa006custom.jpg

See the white sheets (one with the yellow label on). It also hangs down on the sides. It's led.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Nope.

There are lead foil shields wrapped around red and blue, and one across the top, they are likely missing from the tubes you have seen.

.

menec · Joined: 17 Dec 2008 Posts: 74

How bad is it to operate a Marquee without the lead x-ray protection?!

My 8500 came without the x-ray protection and for some months I did not even know that it's actually missing. Then I saw some pictures here on curtpalme.com and bought this lead-thing together with some new tubes.

Tim in Phoenix · Joined: 21 Oct 2006 Posts: 4409 Location: Phoenix

Guys!

If someone has the appropriate test gear and a projector, it would be good to find out how much a hazard is this. TSE?

.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

there was a thread on the english AVForums on this, the giuy ahd a tester and said it was zilch with the shields on,I can't remember with out.

Athanasios

stefuel · Posted: Sat May 16, 2009 11:11 pm Post subject:

Is this lead attached to the tubes or the housings? Could someone post a picture of the lead. Is this only on original equipment and not there after a re-tube? You see I have this project brewing that uses Marquee liquid couplings but no plastic housings. I just want to make sure it's safe.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

Chip, the Led is not wraped around trhe housing at all. it is like a blanket going from the cross memeber that holds the three bulkheads of the tube housings about 10 inches down the tube. they also drop down around the tube on the left and right side of the Pj.

Athanasios

CIR Engineering · Posted: Sun May 17, 2009 3:46 pm Post subject:

Greg Eisemann has has a geiger counter and he says that he's looked at tubes before regarding radiation. He told me that he only can detect radiation when a tube is unshielded if he gets to within two feet or less of the tube with the counter... and it is still very low. I think the radiation that comes out of CRT's is a little over exaggerated. We have such strict standards on electronics and I think back in the day when all the effects from the abomb were on people's minds the radiation standards were being set. I don't know for sure though...

Another thing I have wondered about; is using a geiger counter for CRT testing even accurate. A geiger counter was designed for gamma radiation (I think it's gamma) and CRT's emit X-Ray so they are not the same. However, I still think the emissions for a CRT are minimal and probably not harmful even with massive exposure to CRT.

Also, anything dense will stop radiation, so your CRT metal case will most likely stop radiation as long as it is in place even without the extra lead sheet that Marquee installs. Also, wasn't the lead sheet only required in Canada? I thought USA Marquees did not require the extra radiation blocking?

And, most radiation from CRT is emitted from the front of the tube. A lot is also emitted from the flat ~2" sides that run around the bell of the tube. On all projectors the lens shields the front. On Marquee, the 2" bell is inserted into the thick aluminum bellow which will stop the radiation from exiting the cabinet. Other manufacturers like Sony and NEC use lead tape to wrap around the bell to stop radiation leakage.

craigr

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

The projector manufacturers added shielding as they thought necessary. There were probably some sort of government standards to meet. You can look at the followig attachments to get some idea of what the tubes produce. You may as well figure the anode voltage is +35kV. The anode current is typically 1000uA or less. As mentioned previously dense materials do attenuate the XRays as does distance. Some Wikipedia searching might give some ideas as to how much is acceptable.

Scott

ecrabb · Posted: Sun May 17, 2009 4:59 pm Post subject:

stefuel · Posted: Sun May 17, 2009 6:12 pm Post subject:

Problem solved. I'll post a picture of the solution shortly Cool

greg_mitch · Joined: 03 May 2006 Posts: 5320

stefuel · Posted: Sun May 17, 2009 8:26 pm Post subject:

That should about do it Cool

stefuel · Posted: Sun May 17, 2009 8:51 pm Post subject:

Just look at these attrocities. I make Josef Mengele look like the Pope Laughing

ecrabb · Posted: Sun May 17, 2009 8:59 pm Post subject:

CIR Engineering · Posted: Sun May 17, 2009 10:35 pm Post subject:

I actually thing that Greg's meter is a Geiger counter that he got off ebay from the old "back yard fall out shelter" era of the 1950's. So I do think it is actually a Geiger counter.

craigr

tse · Joined: 03 May 2006 Posts: 1014 Location: Sweatbucket, Fl.

stefuel · Posted: Sun May 17, 2009 11:57 pm Post subject:

mp20748 · Posted: Mon May 18, 2009 12:06 am Post subject:

I have seen in some commercial and government operations where any device that emitted ANY X-radiation had to have a yellow sticker attached to it. That also meant that from time to time, those same devices had to be tested for safety compliance. What I've never seen is one of the CRT projectors that we've serviced or worked on having one of those stickers attached to them.

The main reason I'm sure I've never seen a sticker on any of these projectors, is because the x-radiation tested from them is so low it's not a concern. If it was, you would have seen a yellow sticker on some of the units we see come available.

The Marquee I know has so much shielding than the rest is because the Canadian limits are far stricter than the US and most other countries. Our (USA) governing agency is the Department of Health and Human services. I think they're the same ones that set the requirements in occupational enviroments.

What I've been told is that the level of radiation from a CRT projector is near harmless, unless you poke your head into the lens area for a very long period of time.