Film-Tech Forum ARCHIVE: Harkness Micro Perf Screen -Dust from Speaker Port visible on screen

This is topic Harkness Micro Perf Screen -Dust from Speaker Port visible on screen in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Adrian Hauser (Member # 4723) on 04-29-2016, 04:52 AM:

Hi,
A strange query here.
Recently we have noticed some soft wide vertical lines/marks on our screen, most noticeable with a full white test pattern.
We thought originally that something had gotten in the way of the Christie 2220's light path but a test today dousing the Lamp and shining a torch on the screen revealed the marks still there.
Pulling the screen down revealed the marks were most dense directly in front of where the two centre speaker Ports (JBL) are. The screen is perhaps a little too close to the Speakers and if need be we can move it away by Max 10 cm.
Has anyone else seen this and can you recommend a way to clean the MicoPerf Screen with this anomaly?
Thanks
Adrian

Posted by Dave Macaulay (Member # 813) on 04-29-2016, 06:04 AM:

This happens wherever there's air moving through the screen, like near a bass speaker or badly located HVAC duct opening.
I would vacuum from the back first. This kind of dirt gets stuck in the holes, so a vacuum with a small nozzle without brush sucks it out. Work from the back so you don't mar the front.
Any cleaning on the front can cause problems. The entire surface is likely to be a bit dirty, so cleaning just some of it shows up as a lighter spot.
If you do need to clean the front surface it is possible... unless it's a gain screen or silver 3D screen - results are poor to horrible on those in my experience.

Posted by Monte L Fullmer (Member # 2797) on 04-29-2016, 01:00 PM:

Check with your theatre supplier for a screen brush.

It's a elongated hooped shaped brush about 24 inches long that fits on a threaded pole.

Good for sweeping down screens.

Good luck - Monte