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Discussion Starter · #1 ·
I set aside a good set of sd-187's a month or two ago face down on the shelf out of harms way. ( Needed to fix the broken green front glass before using them.)


Then I go to grab the other two to bleed them to get ready to put them in a pj and notice the red broke just sitting on the shelf at some point. WTF?


I can see that happening in shipping, in use, or in a garage with large temperature variations but we're talking in the house at a constant temperature.


Damn, I guess I won't ever put that off again.


Troy
 

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How big should the bubble be?


The bubble in my VDC P16 is a touch over 1/4" in diameter, when you point the tube straight up and get the bubble in the middle of the tube face.


Is that big enough?
 

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Discussion Starter · #3 ·
Sounds good. The problem seems to be when there is no expansion room left at all. Many tubes like nec pg's seem to have no bubble at all from the factory, and sure enough I had one break in shipping (from pressure not fedex) before I learned that the techs in the know bleed every tube they get as part of the rebuild process.


Only some tubes seem really succeptable from what I've seen... sony 130, 187, 07ms, nec pg tubes... Maybe 180dmb or dvb22 though they seem tougher.


I went ahead and bled the 180dmb's I'm putting into the latest barco I'm fixing and sure enough they had enough pressure that glycol squirted all over as soon as I took out the screw. (I must admit I haven't heard of them breaking yet), but no bubble and plenty of pressure apparently if they're a little old.


If you take out the fill drain screw and glycol squirts up at you then you know you haven't wasted your time that's for sure.


Troy
 

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Strange thing that happen to Troy.:confused:


About heat expansion (sd-187),

I think when doing defungus operation it could be possible to put too thin layer that sealant stuff. Then that sealant layer does not bend elastically enough when happen heat expansion. Then front glass might break.


When I did do defungus operation to my red sd-187, I put equivalent layer that sealant. Then I fill tube totally full (no buble) with glygol (room temp). Pj have used many houndred hours after that without problems. Before operation tube have big buble inside and I got nasty reflection to my screen.


About pressure issue (old tubes),

Maybe that sealant shrink during years and there will come some pressure?

I doubt that nobody (factory?) fill their tubes with cold glygol.
 

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All these tubes had a bubble in them when they were manufactured. Put a bubble back in them. The Glycol absorbs moisture and swells. Like brake fluid.


Marc
 

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Gremlin's


Chip
 

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Gremlins? I use a fogger for those. I think Raid makes one.


No Gremlins for 3 months, guaranteed.


Marc
 

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So how do you stop the glycol getting all over everything if it 'spurts' - I don't want that stuff on circuit boards
 

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Discussion Starter · #9 ·
If you can access the fill drain holes without removing the tubes then have it tilted forward so any run off goes to the front of the tube face, put a towell up against the face to catch any that runs out and hold a tissue around the base of your screwdriver while removing the screw to catch any that flies up.


It'll usually be anything from slowly running out to a small squirt but with a tissue and towell handy you should be able to keep it from getting on anything.


If there is no pressure nothing will happen.


Get a syringe from any pharmacy and withdraw a cc or two to give it an air bubble then seal it back up. Pharmacist may look at you funny, it's up to you not to twitch like a dope fiend.


Troy
 

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A sony tech once told me what I believe to be bit of an urban myth where a sony tech filled tubes on 3 projectors new out of the box and then set them up on the bench to run them in and two of them the glass shattered outwards enough to scratch the lenses badly on some vph-104x's back in the 80's.


I have always left a quarter inch gap of air in the top of the glycol chamber. It might be big but I have seen that gap get so small after hours of use, and you shouldnt be running that close to the edge on the tubes anyways ;)
 
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