Film-Tech Forum ARCHIVE: Reflecting surface falling off from mirror

This is topic Reflecting surface falling off from mirror - Bad mirror? in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Marin Zorica (Member # 1716) on 11-29-2006, 04:02 PM:

I installed new mirror in lamp house with Meopta 380mm diameter mirror and XBO2500 i vertical position. After 15-20 min of working I notticed that about of couple of centimeters silver reflecting surface was gone from mirror, it was fall of easily and after next 20 minutes of working about 30% of mirror was damaged.....lamp house has small mirror as well and cooling fans! I spoked with dealer who sold me this and he told that may bee i miss aligned small mirror (so the light is striking the big mirror - but If I miss aligned the I think less light will strike big mirror than was aligned?) but everything is properly aligned because on another projector is same XBO, with same mirror, lamp house, fans.....and everything is OK! And in all places i worked with this mirrors I newer had problems.

This mirror isn't produced anymore and I think this one is made in 1986....so maybe after long storing time this could happen?

Opinions, ideas.....????

Posted by Cameron Glendinning (Member # 3516) on 11-29-2006, 04:56 PM:

I think its time to get it resurfaced, If its not a kinoton style of mirror which is very different, a regular mirror shop might be a good place to ask where to get it done, only if you have a spare, otherwise a new one is needed.

Personally I am confused by your suppliers comments as I personally have never seen misalignment do this. mirrors do wear out over time due to heat ect.

Posted by Marin Zorica (Member # 1716) on 11-29-2006, 06:13 PM:

quote: Cameron Glendinning
Personally I am confused by your suppliers comments as I personally have never seen misalignment do this. mirrors do wear out over time due to heat ect.

Not only You are confused with it.....

Posted by Jonathan Bodge (Member # 4072) on 11-29-2006, 06:43 PM:

Hi there Marin, Question, how come the original mirror was replaced? Also, if the mirror (which isn't cheap) has a manufacturing (coating) defect do you really think the dealer would admit it? I have collectors (mirrors) in the field, same brand, some flake (over 5 years) and some don't. Your situation seems unusual.

Posted by Louis Bornwasser (Member # 3063) on 11-29-2006, 08:14 PM:

Jonathan; it really isn't up to the dealer. With single digit markups, the dealer can't afford to "eat" anything that expensive and the factories usually don't cover that problem after a certain time....30,60,90 days. This problem is made worse if your dealer actually stocks parts; they may have been on the shelf for months or a year. Louis

Posted by Gordon McLeod (Member # 33) on 11-30-2006, 07:00 PM:

A bi mirror system lamp focus is very critical
The small auxilary front mirror must produce a inverted image f the arc inside the electrode gap in the same exact plane (the small aux mirror is a spherical curve compared to the main reflector being elipical)
If it is focused so the image is on the electrodes they will be burned off faster than one blinks
If focused onto the main reflector it will scale