For definitions of c-element, liquid coupling (LC), or air coupling (AC),
see this
page. Many liquid coupled (LC) projectors were originally manufactured with clear
red and green c-elements in order to increase the overall light output of the
projector. Some home theater enthusiasts choose to replace clear
c-elements with tinted ones in order to achieve more accurate colours (i.e. more
accurate SMPTE-C primaries). This is referred to as colour filtering.
How
much of a difference this actually makes to the projected image is hotly
disputed on many online forums with some saying the difference is huge and
others indicating that it's not worth the hassle. Proponents of colour filtering
will tell you that without colour filtering reds tend to look orange and greens
tend to look yellow. Regardless of the projector in question, only the red
and green are ever colour filtered. Blue is never colour filtered. Below is a
screenshot with the red tube displaying an image. The left half of the
image is un-tinted while the right side shows the effect of tinting.
Red tube output: No colour filtering on the left, colour
filtering on the right
(Thanks to cmjohnson [CJ] for the example photo)
Every manufacturer is different.
In the case of the Marquee 9500LC the c-element on the green tube of is already
tinted green. Only the red needs replacing. In the case of the Barco
1209s, both the red and green c-elements are clear.
Some LC coupled projectors already have both c-elements tinted. The Sony
G70 and the Zenith 1200 are two examples. Note: Colour filtering of LC
projectors can only be achieved by replacing the clear red and green c-elements
with tinted ones. Air-coupled (AC) projectors achieve colour filtering by using
tinted glycol in the coolant chamber in front of the CRT face (ex: Sony
125x/127x, Barco 800) or by using a tinted element with the lenses themselves
(ex: the HD-144 lenses on an NEC PG or XG). Many AC projectors do not use
colour filtering at all.
Sony 1272 air-coupled projector with tinted glycol
Barco 808 air-coupled projector with clear glycol This article
however, deals only with changing of c-elements for Barco LC projectors. Tinting
of air-coupled projectors will be dealt with a future article. Below is the procedure that
you can use if you want to do the c-element change yourself. This is considered a
very advanced procedure as it requires you to completely remove the tube(s) from
the projector. While this procedure was originally written for the Barco 1209s, it can be adopted for other projectors with clear
c-elements if needed. Tinted c-elements are available from both
VDC and 3M. The following procedure and pictures were graciously provided by
Bjørn Hegelstad of Norway. His web site can be found at:
http://www.crtht.com. Bjørn offers home
theater installations, CRT sales, CRT modifications, and gray scale calibrations.
Steps: Here is a little explanation of how I did the C-Element
change.
I have only done this is on a BarcoGraphics 1209s - other projectors maybe
require other procedures.
The new tinted Red and Green C-Elements
1. First I removed the tubes from the projector.
The tube removed from the chassis
The chassis with all tubes removed
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