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Discussion Starter · #1 ·
I'm assuming most all projectors have a Phase and Frequency adjustment. For my projector, the frequency is fine and constant, but the phase is not. I have a bitmap from Mark Reijhon for looking at phase discrepencies, and I can easily see when I'm out of phase. I can adjust the phase setting on my projector and make the output perfect. If I look at it later, however, often it is misadjusted. I'll have to move it 7 clicks to the right or left to get the phase back correct.


Is this a power problem? Is something changing in my input power? Or is it some kind of interference? I'm guessing the former. Right now, I have the projector plugged straight into the wall. I'm wondering if plugging it into a voltage regulator (with brownout correction etc.) will help, or if I would need a top-of-the-line always-generating-perfect-sin-curve power supply.


What exactly is phase? How can you make sure it stays constant?


Thanks!


Mike



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Discussion Starter · #2 ·
Anyone?


Mike



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On my LT150 if auto-adjusted is checked, it'll auto-adjust phase every time when turned on. Is yours in the same boat? I personally auto-adjust to my HTPC every turn on as the projector can do it faster and better than I could with my naked eyes. I just bring the image down to the middle of screen as the auto-adjust tend to put the 16:9 image on top of 4:3 DMD.


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Discussion Starter · #4 ·
Yes, my projector auto-computes phase and frequency, but it does a pretty bad job for phase... Actually, now that I think of it, I wonder if putting it into standby and back causes it to recompute the phase. (It's a slider, so I can't just glance and see the exact value.)


Another point - while being out of phase looks very bad on the test bitmap (or the Windows shutdown screen), I can *never* notice it on either a regular desktop, or a movie... So maybe I should just not worry about it...


Mike



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I think Phase is the timming adjustment of the AtoD (Analog to Digital) converter and the H-sync. In theory, every pixel has a steady state voltage. When the video device changes from one pixel to the next, there is a change of voltage. The pj wants to sample that voltage in the middle of the pixel to avoid sampling switching noises before or after that pixel. When the pj warms up, the phase adjustment may drift. Some pjs may have better tracking than others.


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[This message has been edited by Disto (edited 10-02-2001).]
 

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Discussion Starter · #6 ·
Actually, if I hook up some more cables, I can get a digital reading. I wasn't really sure what that would accomplish, but now I think it would be useful. I'll be able to see if the phase setting is changing, or if the environment is changing.


Mike



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I have to agree with Tony - if you set the phase correctly

once, and it drifts back out of phase - it is most likely

the result of heating.


Heat can cause subtle changes to the electrical properties

of the various elements of the circuit. The once delicately

balanced circuit is no longer in balance after cooking for

a while.


Nothing new or unusual here - that's why they have these

adjustments - if everything stayed rock solid; the factory

would set it and not let you muck with it.


Greg
 

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Quote:
Originally posted by mflaster:

It's a slider, so I can't just glance and see the exact value.
Could you mark it on the screen with a post it and then look for a difference?



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[This message has been edited by Man E (edited 10-02-2001).]
 
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