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it's definitely a heat issue.  be sure to change your filters as often as
your maintenance schedule allows (optimally once/month or more) and make
sure your projectors are in a well-ventilated area.

but yeah...LCDs just tend to discolor with age (faster if they're running
too hot).  that's one of their disadvantages.  you can always get them
repaired by the manufacturer, particularly (of course) if they're under
warranty.

-eric

Date:    Tue, 13 Apr 2010 09:57:25 -0700
> From:    Allan Ayres <[log in to unmask]>
> Subject: Yellow spots in video projectors?
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> Hi everyone,
>
> I posted this yesterday on the Science on a Sphere list, but I figured
> I'd ask here as well.
>
> I'm wondering if other video projector users have had yellow spots
> develop in their images over time.  We've particularly had problems
> with Sony projectors, including two of the VPL-FE40 units in our SoS
> installation and an older VPL-PX40 we took out of service a few years
> ago because of the spots.  (We don't have experience with any other
> brands, so I don't know if they have similar problems.)
>
> I dug out the old VPL-PX40 and took it apart, and it appears to be the
> blue LCD element itself that has the splotches in it.  That's a
> bummer, as I suppose an LCD panel is more expensive to replace than,
> say, one of the polarizers or other little plastic filters that are
> scattered around the system (i.e. probably some significant fraction
> of the cost of a new projector).
>
> Anyway, I just wanted to throw the question out to see if anyone else
> had faced this problem.  If so, has anyone had any success with
> getting projectors repaired and/or cleaned?
>
> Thanks!
> ~~~~~~~~~~~~~~~~~~~~~~~~~
> Allan Ayres
> Exhibit Developer
> Lawrence Hall of Science
> University of California, Berkeley
> Berkeley, CA 94720-5200
> [log in to unmask]
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> Date:    Tue, 13 Apr 2010 11:07:57 -0600
> From:    Bruce Wyman <[log in to unmask]>
> Subject: Re: Yellow spots in video projectors?
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> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
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> institutions.
>
> *****************************************************************************
>
> >I'm wondering if other video projector users have had yellow spots
> >develop in their images over time.  We've particularly had problems
> >with Sony projectors, including two of the VPL-FE40 units in our SoS
> >installation and an older VPL-PX40 we took out of service a few
> >years ago because of the spots.  (We don't have experience with any
> >other brands, so I don't know if they have similar problems.)
>
> I've seen it as a problem with LCD projectors, never with DLP
> projectors. We usually see it as a blue haze forming around the
> periphery of the projected image which eventually spreads across the
> entire image like a cataract (primarily with Viewsonic projectors
> (PJ1172, which are really rebranded hitachis)).
>
> I have the unique case of being at higher altitude than most other
> people (we're about a mile above sea level) and I think the
> underlying issue is one of heat. At altitude, we just have less air
> to move around to cool off the projectors (and lower end projectors
> don't have a secret altitude setting in firmware). Every LCD
> projector I've used eventually has problems with the screen closest
> to the heat source in the projector. The problem is definitely
> compounded if the projectors are being used outside of the
> recommended angles and positioning of the manufacturer.
>
> I've talked with Sony, Hitachi, and Panasonic reps and I've never had
> a consistent answer so the above is a bit of conjecture. But, for
> stuff that we're using in exhibits and where airflow may be a
> potential issue, we're using DLP projectors exclusively.
>
> -bw.
> --
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
> Bruce Wyman, Director of Technology
> Denver Art Museum  /  100 W 14th Ave. Pkwy, Denver, CO 80204
> office: 720.913.0159  /  fax: 720.913.0002
> <[log in to unmask]>
>

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