[HELP] Random green image - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 9 Old 10-28-2019, 03:36 AM - Thread Starter
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Question [HELP] Random green image

Hello there,

I recent bought a VIEWSONIC PJD7822HDL projector (Open boxed) and sometimes, randomaly, the projection turns green for about 1s.
i search and someone aid to turn on High Altitude Mode to make the fan speeds up. This reduced the amount of times the problem occurs but still, sometimes the green projection shows again.
My questions are:

- What is the real problem and how can i fix it?
- Can i improve the fan to other more powerfull in therms of airflow?

Thanks for the help (im a n00b in DLP projectors and love to learn more)
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post #2 of 9 Old 10-28-2019, 05:31 AM - Thread Starter
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Infos and what i tried till now:

The projector is seating on a table with 60cm of hight +/-
Room temperature is in between 20-24ºC i think

i already tried different HDMI cables and the 2 HDMI input's with a nintendo Switch on Full Color Range and a Laptop.

BTW the problem is like this one but only with green and far less times showing
http s://w ww.yout ube.com /watch?v=plxc__EMRbI
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post #3 of 9 Old 10-28-2019, 06:10 AM
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Hope it is still under warranty. Most likely a defect in the HDMI inputs circuit. First I would suspect poor HDMI connections but if you tried multiple cables unless they are both cheap or defective cables it looks like a hardware issue with the projector. I doubt color wheel issues because it would just get random colors not just green. One other thing to try is force the projector into RGB instead of auto as I think if the input is RGB and the projector switches to YCB you get a green screen.

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post #4 of 9 Old 10-28-2019, 06:10 AM
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I think this is the video:
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post #5 of 9 Old 10-28-2019, 06:19 AM
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Hi Hugo,


my first guess is that there may be some faulty contact between the mainboard and the DMD chip, or between the mainboard and the color wheel, and that this faulty contact becomes increasingly worse as the projector heats up. Still, it's just a guess. You already tried different HDMI cables, but I would also try using the projector without any cables connected. If this issue occurs with just the projector menu, then you can completely eliminate an input problem. Sometimes, this can be fixed by reseating the cable.

My second guess would be that there is a mismatch between the internal signal and the color wheel, and, depending on the cause of this mismatch, it may or may not be fixed through the service menu.

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post #6 of 9 Old 10-28-2019, 06:38 AM - Thread Starter
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Quote:
Originally Posted by rekbones View Post
Hope it is still under warranty. Most likely a defect in the HDMI inputs circuit. First I would suspect poor HDMI connections but if you tried multiple cables unless they are both cheap or defective cables it looks like a hardware issue with the projector. I doubt color wheel issues because it would just get random colors not just green. One other thing to try is force the projector into RGB instead of auto as I think if the input is RGB and the projector switches to YCB you get a green screen.
Unfortunately is not, i bought it on ebay as Open Box for 190€.
When i get home i will force both the projector and Switch to display only RGB in full color range and limited.

Quote:
Originally Posted by descalabro View Post
Hi Hugo,


my first guess is that there may be some faulty contact between the mainboard and the DMD chip, or between the mainboard and the color wheel, and that this faulty contact becomes increasingly worse as the projector heats up. Still, it's just a guess. You already tried different HDMI cables, but I would also try using the projector without any cables connected. If this issue occurs with just the projector menu, then you can completely eliminate an input problem. Sometimes, this can be fixed by reseating the cable.

My second guess would be that there is a mismatch between the internal signal and the color wheel, and, depending on the cause of this mismatch, it may or may not be fixed through the service menu.
Hello there,

Any test that i can do more to mitigate the problem that let us know what really hapening?


Will try to record the problem but like i said is random and quick.
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post #7 of 9 Old 10-29-2019, 04:42 PM
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Quote:
Originally Posted by Hugo Rocha View Post
Unfortunately is not, i bought it on ebay as Open Box for 190€.
When i get home i will force both the projector and Switch to display only RGB in full color range and limited.



Hello there,

Any test that i can do more to mitigate the problem that let us know what really hapening?


Will try to record the problem but like i said is random and quick.
Sorry, I don't know of any test pattern that may help conclude much else about this issue. A Red and Blue test pattern may help you understand if the signal is turning to green or if it's losing its Red and Blue data. If it's losing its red and blue data, there's a greater chance of a bad contact on the DMD cable connection, in which case it may be worth to open the projector and reseat this cable. Otherwise, test patterns won't tell you the definitive origin of the issue. Testing the projector without any inputs is crucial in order to exclude the inputs as the cause of the issue.

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post #8 of 9 Old 10-29-2019, 07:40 PM
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Quote:
Originally Posted by descalabro View Post
Sorry, I don't know of any test pattern that may help conclude much else about this issue. A Red and Blue test pattern may help you understand if the signal is turning to green or if it's losing its Red and Blue data. If it's losing its red and blue data, there's a greater chance of a bad contact on the DMD cable connection, in which case it may be worth to open the projector and reseat this cable. Otherwise, test patterns won't tell you the definitive origin of the issue. Testing the projector without any inputs is crucial in order to exclude the inputs as the cause of the issue.
The DMD only produces pixels it has nothing to do with color other then syncing with the color wheel. A poor connection to the DMD would result in corrupted pixels not a color issue.

"Smart enough to know better, to old to care" ------ Dedicated Bat Cave Home Theater, JVC RS49U/Mitsubishi HC7900DW Projector, 110" 16:9 Jamestown screen with variable power masking for CIW 2.50:1 to 16:9, Marantz 7009 with 7.1.4 Atmos with Ohm mains,3 DIY Subs (2 15" (1 ported, 1 sealed and a 12" 4th order bandpass), 1 DIY butt kicker, Custom Built HTPC, 18TB DroboFS NAS
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post #9 of 9 Old 10-30-2019, 03:41 AM
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[HELP] Random green image

Quote:
Originally Posted by rekbones View Post
The DMD only produces pixels it has nothing to do with color other then syncing with the color wheel. A poor connection to the DMD would result in corrupted pixels not a color issue.


It’s the syncing I’m talking about. What if the signals for Red and Blue pixels aren’t passing properly, wouldn’t that make the DMD chip cut the light off for those 2 colors when the issue occurs?


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