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Discussion Starter · #1 ·
Hey ppl


I thought I would ask this question here and maybe see if this has happened to anybody else or maybe someone would explain how the f**k this happened. I had just finished centering the raster on my NEC 9pg folling the pdf manual that Tinman wrote, when I had done that I pressed the Pic mute button and went on to read the next paragraph and then heard a crack, yes the face of the blue tube cracked. I cant understand why this would happen except that maybe the glass was warm and being not a warm night it might have reacted. I have attached a pic of the cracked tube, has anybody seen this happen before. I am really worried that if I dont find out the cause and I go ahead and buy new tubes that its a fault with the projector and will crack the new tube.


Nick
 

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Nicke, it appears there is burn in a relatively small portion of the tube. Could it be there was too much energy/heat on one part of the tube face and not adjacent areas that created a difference in temperature between the two? Just a thought.

Marvin
 

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Whoa!


Never saw that one before. Also the raster was run too small. Was the fluid level full? Looks like stress cracked it. How large was the raster at the time, and how bright (contrast) was it run? You CAN replace that glass, btw. Did it get hit with cold air from an AC duct by any chance?


Marc
 

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I've heard of this happening if the raster was either off-center or too large for the tube face and hitting the non-phosphor area.


Cary
 

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The thing here is that the FRONT glass broke, and not the tube itself. It's fixable. It's almost as if there was not enough of an air bubble in the glycol chamber to allow adequate expansion of the fluid, and bam. It should be fixable just like the Sony SD-187 tubes, maybe not as easy to cut the seal, but the same thing. A new glass can be cut at a glass shop. It's been done before, just tedious. Although I'm not sure I would WANT to use that blue with such a small raster worn into it. It'll certainly show up when it's expanded.

But the CRT is not a loss. Guys, keep in mind that there MUST be a bubble in each tube to allow the glycol to expand as it gets hot. I'm really thinking this is what happened due to the circular break in the center. Looks like pressure induced failure.


Marc
 

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I had this on a sd130 out of a little vph1020. The front glass of the tube broke due to the expansion of the glycol. :(

It was fixable on sony tube, I don't know on nec ones, but as said by Tinman i won't use that tube, it has been badly used !!


Ciao!
 

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I just took a look at a spare tube in the garage, and yes, it's fixable just like the sony tubes.


Marc
 

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Thanks for all the replies guys Nick is still is shock I think, he rang me when it happened. It sounded to me like it was warm and a cold draft of air hit the tube. He was centering the raster with the lens off, so not caused by off center raster. But as he said it was cold in the house and with the lens off it would be unprotected from the cold air.


GYZMO
 

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Sounds plausible. Tell him to get out a razor blade and some black hi-temp silicone. A trip to the glass shop will fix this. The CRT has to be removed and unscrewed from the metal housing it sits in. The rest is totally obvious. And.... maybe warm the house a bit next time.


Marc
 

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...or leave the lenses on. I would think that would have to be an awfully cold BLAST of air as the tube face really doesn't get very warm...in fact running one at high contrast, full white screen for 10 minutes produced no warmth on the tube face of both a Marquee 8500 and a Ampro 3600...the outer surface just doesn't warm up.
 

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Discussion Starter · #14 ·
Hi guys, just as gyzmo said I just got over my shock .. thankyou to all that replied. I think it might have been that there was no room for expansion in the glycol chamber as tinman said as for the wear, was like that when I got it I was looking at retubing anyway ... just not so soon :( .. the only adjustments I did do when I was centering was the brightness and contrast, they where contrast 0 and brightness 100 .. I never touched the G2s or take the raster to close the the end edge of the phosfer ... but I was there a while and using a short ruler to make sure I was dead set in the center and not more the 1/2 an inch from the edge (was exactally 20mm each side).. it was cool in the house and the fan under the tube face was blowing but that was in the downward direction ...


vern .. answer is still in the chamber .. only lost acouple of drops...


Thanks again to all that replied


Nike (The tube cracker)
 

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Quote:
Originally posted by Nicke
I did do when I was centering was the brightness and contrast, they where contrast 0 and brightness 100 .. I never touched the G2s Nike (The tube cracker)
Just something for you to add to your bank of knowledge...when you change brightness settings, you are in fact changing G2.

Brightness is really a fine tuning of G2.
 

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Discussion Starter · #16 ·
Hi all, update on the horror of the tube .. instead of 1 cracked tube I just found now I have 3 .... I hadnt done anything since last night and just had a look at it tonight and there were two more cracked tubes .... Now the other 2 cracked by themselves and that I cant explain.. although I am now back in "SHOCK MODE"


Nick
http://www.gyzmo.com.au/G70/DCP_1941.JPG
 

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I've cracked a blue tube, and initially thought we had done it in a similar manner since I'm sure I cracked mine by running the beam off the side and overheating it, BUT with all three of yours cracked, I'd be placing my money on some overtorqued screws in that puppy. Check to see how tightly the screws which hold the crt's in their aluminum frames are, and how tightly the screws for the toe in are srewed into the same basket. I'd bet all those screws are super tight, and the pressure cracked the tubes, let us know if you find anything conclusive.
 

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Wow.... this is weird....


Marc
 

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My condolences...this is painful to watch. Sort of like staring at a car accident. I am getting scared to turn on my projector.
 

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Nicke,

I have seen this before many times, just not all 3 at the same time. I use to save these to look at like pictures on the top shelf if the tube has wear. The ones with the tube envelope broke really look cool but the glycol made a mess.


I need to ask if they cracked with the lenses on or off or if you removed them then reinstalled and it sat.


There are 3 things that will do this, glycol expansion, raster off to the side with no memory to hold it, and stress.


Knowing the steps you took will narrow it down to one thing, we can eliminate the raster off to the side because this would have cracked the tube itself and not the chamber glass. So we are down to two possible reasons.


The glycol expansion is heat related and raster size or the combination of both.


Stress is reshaping the glass to fast either by touque or the weight of the tube hanging without the counter balance of the lens weight.


In either your lucky the tube itself isnt cracked.


This is under normal conditions, if you left the tube faces exposed to a a/c vent when hot it could do this also, The glass itself doesnt get that hot but the surrounding metal does, I guess that would be called stress.


We all learn from these things so I really have to say thanks for the post. Doug
 
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