.

You've got it backwards. Glycol leaks are common on Air Coupled (AC) projectors. This does not happen to Liquid Coupled (LC) projectors.

I'll explain. All CRTs used in front projectors have glycol to cool the front of the tube. AC projectors have a flat piece of glass glued to the front of the tube, between this glass and the tube is the glycol. On this type of projector it is important to make sure that there is an air bubble above the glycol.

On a LC CRT there is a C-shape lense fixed to the front of the lense with a large rubber gasket. This gasket is soft and holds the glycol between the CRT and the C-Element. You don't need to worry about this leaking since the rubber expands if the glycol expands. (It can happen but its very rare compared to AC sets)

You really should go explorer Curt Palme's site it has really good pictures and explenations of all this stuff.

Brian

NEC and Sony LC sets require no maintenance basically.

Marquees, and some Barcos (correct me if I'm wrong) can get corrosion in the chamber leading to cloudy glycol.

I didn't realize that. I thought only LC did. Woops. Then why is it called "air coupled" if both use glycol?

So are there any dangers to LC sets? LC sets are then actually less prone to tube damage?

Glycol is used on ALL CRT's as a cooling meduim for the face of the tube.

Air Coupled means that there is an air gap between the glass on the front of the tube assy (the glass hold in the glycol) and the rear of the lens.

On an Liquid Coupled machine, instead of having a piece of glass they put the rear most lens's element (known as the CElement) on the tube housing so that it is in the glycol.

On an AC machine the light is going through glycol, a piece of glass and then air prior to hitting the rear lens element and that can cause halo's (I believe this has to do with the refraction index of the different mediums glycol and air?) whereas on an LC machine the light stays in glycol up to the rear lens's element.

http://www.curtpalme.com/TubeCondition.shtm this page shows the front of an AC housing. Notice the flat glass (this isn't the tube face)?? behind it is the glycol.

http://www.curtpalme.com/Changing_C_Elements2.shtm is a picture of a 9500 tube housing which is LC. Notice the curved CElement?? the glycol is low in this picture so you can see the space between the CElement and the face of the tube.

Terry

You want to read this article on "How to bleed AC tubes": http://www.curtpalme.com/Bleeding_CRT_Tubes1.shtm

There's also an article on "Venting LC tubes": http://www.curtpalme.com/Marquee_LCvent.shtm

In fact, all of the Advanced Procedures are useful! :)
See: http://www.curtpalme.com/Advanced_Procedures.shtm

There's a bit fat icon right on the main page of www.curtpalme.com entitled "Advanced Procedures" if ever you forget where to find this info. There's also the site search engine. You can also search for "Bleeding LC tubes" on Google and you'll come up with some of these pages.

Search engines are your friend!

Kal