CurtPalme.com Home Theater Forum

[Ben851]

So you may have seen my previous thread asking about whether or not I could swap tube hardware with a PG and XG after cracking two of the glass plates on my XG housing - well today I decided to do the deed and rip apart my spare PG. I pulled all three tubes, brought them upstairs and set about removing the HV leads. I do this on all three tubes, and then set about fastening them to my new tubes.. Go back to the old tubes to find all three pieces of glass CRACKED. They were pristine when I brought them upstairs - I'm guessing that they weren't bled and the change in temperature from the basement to upstairs did them in.

So what are my options? Is this some special type of glass (optical?) Or can I take the one good piece I have to a glass shop and have them cut me two more? Does anyone happen to have a couple spare pieces of glass for an XG (or PG)?

I have my actual functioning PG that I could take down if all else fails but I REALLY don't want to take the chance on that... A functioning PG is better than a non functioning PG and XG.

[Ironman1965]

Well, with the luck I've had with my tube swap you may not want my advice, but I'll give it any way. I had a problem with broken glass and on the suggestion of Curt I bought a sheet of clear Lexan (polycarbonate) that is .11" thick. I cut pieces of the Lexan the same size as the original glass (on a table saw (be gentle cutting as chips quite easy)) then bucked off the corners at 45 deg. Make sure if you do this that you don't remove any of the protective film from the Lexan until you are completely ready to silicone it to the aluminum casting. Give your hands a good soap and water wash to get rid of any contamination or body oil from your skin, also vacuum the living daylights out of the Lexan before removing the film (to remove all traces of cuttings and dust) as well and make sure you are in as dust free of an environment as possible before removing the film and applying the Lexan to the casting. This stuff gets quite the static buildup when removing the film (if plastic, not sure about paper) and seems to attract dust from the next continent over (this was my learning experience doing this) Went through 3 or 4 pieces before I got it right and had no visible contamination or scuffs or finger prints in the glycol chamber on completion (it was truly flawless even under a relatively powerful magnifying glass ). The Lexan works fine and is even clearer than the original glass (don't know the tech speak for this property) so will allow more light through. Everything else went FUBAR on the PJ, but the Lexan held it's own. The stuff is very strong. It will scratch easier than glass so you must be careful. The one good thing is that if you develop a small scratch or scuff, there is a product made by Novus (there are other makes as well) specifically for removing heavy and fine scratches as well as a specially designed cleaner for plastics. I bought the complete kit of 3-8 oz. bottles (which is lots) that comes with 2 or 3 lint free cloths and instructions, on the bay for $26.42 shipped to Canada. This stuff is designed to be used on any acrylic. And I figured it probably wouldn't be a bad thing to have kicking around "just in case".

There is a glass option as well but didn't research it as much so not sure of the cost but it's probably not cheap as it is optical grade so here is a link if you must use glass...

[Ben851]

Hey Ironman,

Thanks for the tip - where did you pick up your lexan in Canada?

EDIT: After doing some more research, I've found that lexan "insulates better than glass" - to the experts out there - could this have been what caused Ironman's green tube to fail? The glycol not cooling as efficiently and thus overheating the tube?

[nuttall_chris]

[Ben851]

Thanks Chris,

I think the first thing I'm going to try is hidden option #3 - I have some Marquee tubes left over from a parts machine. I'll try grabbing the glass off of those and taking them to a glass shop to be cut down to XG size... If that doesn't work it will be off to HD for some Lexan I guess!

PS: Chris, did you still want a set of HD6s?

[Ironman1965]

[Mark_A_W]

The glycol absorbs water through the silicone (silicone is permeable to vapour), increasing the volume of liquid in the chamber.

The temp change causes the fluid to expand a bit, and the glass cracks.


You have to bleed your tubes. And leave a reasonable air bubble (20mm across or so).

[Ben851]

Mark,

Are you responding to the original post or to Ironman's post? Ironman, did you bleed your tube?

[benareeno]

NEC glass should be easy to come by...I wouldn't substitute something else in there...isn't there some amount of curvature to the glass or no?

Anyhow, I had extra tubes here and was able to swap glass. It was not without a hiccup or two...but I did it.

Find someone with a set of roasted tubes and get the glass!

[Mark_A_W]

The glass is flat.

But it does have an optical coating.


One of the Aussie guys did experiments and found that polycarbonate was as good or better than the original glass.

[erichf531]

My Nec 6PG cracked the glass on the green tube last fall and I am finally getting around to fixing it. I e-mailed VDC to see about getting replacement glass and they wanted me to just send it them for repairs along with $100 US. I think I am going to try the Lexan
as I am on a tight budget and I am not sure weather I am going to keep the projector or not. I released the pressure on the other two tubes so i dont have to worry about them cracking on me. Where Would I find replacement glycol? I think I only need about 2.5 oz or so. I managed to save almost all of what was in the tube but I will probably need a little more.

[Ben851]

thechemistrystore.com is where I got mine... after a lot of pain and suffering, the glass and glycol have been replaced for my tubes... still haven't gotten them in the PJ though

[erichf531]

Thanks, I check it out. I hear ya on the tubes, removing mine has sure been a learning experience. Hopefully the set doesnt smoke check after I get it back together, LOL!