Optoma HD72 Colors Wrong after replacing color wheel - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 9 Old 08-10-2014, 11:16 AM - Thread Starter
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Optoma HD72 Colors Wrong after replacing color wheel

My color wheel broke (clear segment detached), so I ordered a replacement from Ebay. They appeared to be identical, but after installation, the colors are very off. There's a red/brown cast to the whole image (even the menus and startup screen), and images (regardless of input signal) have a lot of banding and solarization to the colors. It's impossible to calibrate it to good results.

Did I receive the wrong model of color wheel, or is there likely some other problem that has been introduced while I was replacing the wheel?

The projector runs fine (no warning lights or automatic shut-downs).
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post #2 of 9 Old 08-10-2014, 12:48 PM
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Initially it sounded like the wheel might not be synchronizing consistently when powered on; but that's not the case if the same red/brown menu color-cast is appearing every time (and that color cast doesn't change to another color for the menus each time you power on).

It's very likely, then, as you suspect, that the color wheel replacement model is not an exact match to the one it replaced.

The firmware in any single-chip DLP projector is built to operate with only one wheel layout and the DMD is thus synchronized for that wheel only. Even small changes - say, a color wheel with the exact same order of segments but one of them being slightly larger in the replacement - would cause issues similar to what you're seeing.

BenQ W1070 Projector; Xtreamer Ultra 2 (running XBMC on OpenELEC) via Sony STR-DH540 AVR with Boston Acoustics SoundWare XS SE 5.1 Audio. MediaBrowser3 for Mobile Streaming.

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post #3 of 9 Old 08-10-2014, 01:08 PM - Thread Starter
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That totally makes sense as far as the color cast is concerned.

However, what about the banding and solarization that I'm seeing in the projected image? Would a color wheel mismatch cause that also?

Here's a photo of the new (left), and original broken wheel (right).

They appear to be very close, though the old one seems to be perhaps 1mm larger in diameter, and the segments may be slightly different in size, though they appear very close.
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post #4 of 9 Old 08-10-2014, 01:13 PM
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There we go!
That is absolutely not a matching color wheel: the segment sizes differ.

Yes, that will certainly explain your issues

BenQ W1070 Projector; Xtreamer Ultra 2 (running XBMC on OpenELEC) via Sony STR-DH540 AVR with Boston Acoustics SoundWare XS SE 5.1 Audio. MediaBrowser3 for Mobile Streaming.

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post #5 of 9 Old 08-10-2014, 01:28 PM - Thread Starter
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Allrighty - I will send back the color wheel and see if they can get it right this time or refund my money. Frustrating.

Any recommendations on reliable sources for an HD72 color wheel?
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post #6 of 9 Old 08-29-2014, 08:41 PM - Thread Starter
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Quote:
Originally Posted by cooperdw View Post
Allrighty - I will send back the color wheel and see if they can get it right this time or refund my money. Frustrating.

Any recommendations on reliable sources for an HD72 color wheel?
So ... I returned the color wheel I had ordered, got a refund, and ordered another color wheel from another vendor. This one actually *appears* to be more correct (just from memory, no measurements), but who knows. It dropped in easily, and the projector powered up without fuss.

Color problems are still there. There's an overall magenta cast to the image - even the menus and splash screen (which is magenta instead of blue), and I'm still seeing terrible banding in the images. Here are a couple of photos of grey ramps, showing strange banding and color artifacts in different parts of the value range depending on what I've got running for brightness / contrast controls. It's impossible to calibrate this properly.

Any ideas if another component (possibly the image processor?) has failed in the projector as well? I'd love to keep this one going if I can, otherwise it'll be time to start shopping.

Attached images ...

high_contrast - default contrast settings on the projector, large area of highlights are clipped, and magenta/green color banding near the highlights.
lo_contrast - very low contrast setting (-27), eliminates clipping at the high end, but moves the strange color bands to the mid-tones.

Unfortunately, these are iPhone photos, so white balance has tainted the overall color balance, but you get the idea ...
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post #7 of 9 Old 08-30-2014, 07:16 AM
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You need to find out how to access the service menu to adjust the color wheel timing. This causes the banding and solarization. My Planar had an issue with solarization and correcting the timing fixed the problem. The hard part will be finding how to access the service menu.
To fix you put up a colored ramp pattern that shows the issue and change the timing till the issue goes away..
Good luck

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post #8 of 9 Old 08-30-2014, 09:03 AM - Thread Starter
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Thanks for the suggestion, I'll take a look.

For anyone else who needs the service manual for their HD72 (which has instructions for entering service menus), I found it here:

http://www.manualslib.com/manual/698...toma-Hd72.html
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post #9 of 9 Old 08-30-2014, 09:50 AM - Thread Starter
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Adjusting the Color Wheel Index in the service menu did the trick, thank you!!!

Back up and running now - it's about time we can watch the new Doctor Who series
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