|
Author
|
Topic: GS1200 Simple Fix for light uniformity
|
Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
|
posted April 25, 2013 12:04 PM
I have noticed on both my GS1200’s that the light on the screen is not uniform. In particular both projectors exhibit a less brightness on the right hand side of the screen. I had attributed this to the bulb not being perfectly in the center of the lamp reflector, in other words a problem with the bulb. But then I just purchased a couple of the new Fuji ESC lamps from Steve Osborne, and found the same problem, even though the overall brightness was far superior to the EJL lamps that I have been using. I tried rotating the lamp 180 degrees in the lamp holder, but it was still darker on the right side of the screen , so it was not a bulb problem. The fact that it was less bright on the right side of the screen seemed to indicate that the bulb was not centered on the lens axis, but was in fact positioned too far outward from the chassis wall.
The GS1200 lamp bracket is mounted to the chassis by two bolts along the top edge. One of the holes is oversized to permit vertical rotation alignment of the lamp. But there is no provision at all for horizontal alignment. Even worse, the lamp holder is located off the two small diameter bosses on the chassis wall, and there is no third mounting point on the bottom side of the lamp holder to ensure a precision horizontal positioning. In fact the diameter of the two chassis mounting bolts are so small that it is very unlikely that the lamp is positioned accurately in the horizontal direction. This is an incredible oversight by the Elmo designers, particularly considering that they were designing an ultra high end machine. Contrast this with the Eumig designs, where the lamp is located into a very rigid and precision feature casted as part of the chassis.
Anyway, I removed the lamp holder from the GS, clamped the top mounting flange edge into a vice and bent it over to an angle of about 5 to 10 degrees, thus moving the lamp closer to the chassis wall. This is such a small angle that the vertical position of the lamp is barely affected. When I remounted the lamp holder and switched on the projector the screen illumination was perfectly uniform - problem solved!
If your GS1200 suffers from non-uniform lighting, this will fix the problem.
As mentioned above I have now started using the new Fuji ESC lamps, which I got from Steve Osborne. I did not measure light output as I do not have a light meter, but I can say, like previous users, that the ESC is very noticeably brighter and whiter than the EJL lamps, so much so that I will never use the EJL lamps again.
--------------------
The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection,
Elmo GS1200 f1.0 2-blade
Eumig S938 Stereo f1.0 Ektar
Panasonic PT-AE4000U digital pj
| IP: Logged
|
|
|
|
|
|
|
|
|
UBBFriend: Email this page to someone!
Printer-friendly view of this topic
