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Joachim
Joined: 22 Oct 2007
Posts: 10
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| Posted: Fri Aug 30, 2013 10:39 am Post subject: Barco 801s Slight banding on some refresh rates |
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Hi
I just noticed yesterday that my 801 show some slight banding issues. (I think it's banding, after I read the Marquee banding mod article.
In 1280x720@75Hz, the bottom part of the image is slightly brighter than the top part and there is a distinct line about mid-screen. It sucks because I think that's the sweetspot res and refresh for the beast 
This does not show up at 60Hz or 85Hz at the same resolution. Neither have I seen it in lower resolutions or 1600x900x60
I'm running the VGA out trough an INLINE 2160 "High Resolution VGA interface" that takes the VGA signal and gives it composite RGBS sync. It also has a setting for serration pulse removal which I have tried to see if it makes any difference but it doesn't.
I also tried redoing calibration, adjusted G2 voltages and ES Focus. As far as I can tell most of this comes from the green signal, or it is just mostly visible there. I cannot see it on any other tubes.
Any ideas why I get this slight artifact? The tubes are mint, about 1500hrs.
Oh, by the way. I also did a fan mod, I suppose not related to my banding issues. I exchanged the fans to more quiet SilenX 74cfm 15dB ones. And they are RED! Of course they are not 15dB, but at least a bit less noisy than the original ones. I just need to check the temps because I think they are a bit less effective too. Even thought the 74cfm rating is close to the original ones. I also removed the input 3 video board and the wired remote to get better airflow.
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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RaWsHaRk
Joined: 01 May 2009
Posts: 131
Location: Finland
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| Posted: Fri Aug 30, 2013 6:13 pm Post subject: |
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take those fans away and put the stockers back, that is asking for trouble.not many fans can beat the push/noise ratio of the originals.
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Fri Aug 30, 2013 6:18 pm Post subject: |
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My before/after temperature results of replacing my Barco fans with SilenX brand are here:
http://www.curtpalme.com/forum/viewtopic.php?p=39848#39848
| kal wrote: | Hi Walter,
Good timing! Below are my findings after a week of testing with a couple of temp probes.
I measured the temperature directly on a variety of the heat sinks at the same scanrate each time. This took me all week because (a) it somtimes takes up to 2 hours for each temp to stabilize, (b) I did 2 whole sets of tests from start to finish to make sure that temp probe placement didn't change too much based on positioning (it didn't), and (c) I had to put the all 3 old NMB stock fans back into the projector and redo all temp tests.
H-Shift/Focus board (middle): 46.0C (NMB) -> 54.5C (SilenX)
H-Shift/Focus board (bottom): 46.2C (NMB) -> 53.3C (SilenX)
Horiz board (on top): 28.0C (NMB) -> 42.5C (SilenX)
Vertical board (on top): 39.6C (NMB) -> 50.2C (SilenX)
SMPS (underneath): 36.8C (NMB) -> 41.1C (SilenX)
All tests done with a 1080i/60Hz signal as input.
Remember that I replaced the fans as follows:
Angled 80CFM NMB fan -> 72CFM SilenX fan (this one only cools the H-Shift/Focus board)
2 other NMB 80CFM fans -> 90 CFM SilenX fans (these cool everything else)
Some of these temp jumps are huge! For example, the horiz board which is basically cooled by one of the 80CFM NMB or 90CFM SilenX fans jumps 14.5C even though the new fan is 'supposed' to be 10CFM larger!
Same with the SMPS. The "Larger" 90CFM SilenX fan cools worse than the 80CFM NMB fan.
The NMB fans are staying in place. Anyone want to buy $120CAD worth of SilenX fans? |
Kal
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Joachim
Joined: 22 Oct 2007
Posts: 10
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| Posted: Sun Sep 01, 2013 2:39 pm Post subject: |
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Thanx this was excellent info. I was going to ask where i should monitor temps but after this there is no need to.
Sounds like I'm reverting to standard fans then and take the few extra dB's. Is there a third fan somewhere?
So although cfm is close to original fans on the silenx they have less pressure capability?
Thank you guys!
Regarding the "banding". Do you have any thoughts on that for me? Why the bottom of the picture is slightly brighter than the top, but only in some refresh rates?
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Sun Sep 01, 2013 6:18 pm Post subject: |
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CFM rating on SilenX may be the same, but that's only when running them in open air without any resistance at all. As soon as you put any resistance on them the CFM drops a lot while the original fans do not drop as much. This is called 'static pressure' if you want to look it up more. A good fan will have a curve that shows how the CFM drops over pressure. A poor fan like the SilenX will drop off faster.
Kal
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Mon Sep 02, 2013 8:03 am Post subject: |
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It's setup issue, too much electrical adjustment used. Two horizontal lines are overlapping.
search "barco horizontal line of coincidence"
Something to check:
-yokes horizontal leveling
-don't tilt projector downwards on ceiling installation
Even everything is fine this could exist with some resolution.
Playing with bow or keystone settings usually get it disappear.
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kal
Forum Administrator
Joined: 06 Mar 2006
Posts: 18114
Location: Ottawa, Canada
TV/Projector: JVC DLA-NZ7
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| Posted: Mon Sep 02, 2013 2:13 pm Post subject: |
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Ile is right: You're pushing some of the electronic menu controls too much. You need to do better with the physical alignment of the tubes first.
I found a quote from myself:
| Quote: | Q: I have an odd horizontal line visible at times, what is it?
A: At times you may see a horizontal line that fades in the middle of the picture but it quite visible at one end (often the right side), it will be most visible on bright scenes, all white fields or light blues. This is called the horizontal line of coincidence, to some extent it's natural on some models of projector but careful adjustment can remove or at least minimise it. Pause a scene where the line is plainly visible, note which side it shows the most, go to a genlocked pattern and adjust horizontal skew to lower the horizontal centre line on the opposite side to the worst one. Do this by only a small amount, say 4-5 clicks. Now adjust top and bottom keystone to correct the error the skew change introduced. Go back to the picture, is the line less? If it's worse you skewed the wrong way, if it's better carry on tweaking the skew and keystone to minimise or remove the line. You may end up with a horizontal skew error that's plainly visible on the test pattern, it should not be obvious on actual video. Excessive use of horizontal bow may also make the line worse, again it should be possible to reduce the effect by adjusting horizontal bow and correcting the resulting top / bottom bow errors. Removing the line completely may not be possible but you should be able to reduce it to an acceptable level. The line is caused by the projector set-up making several scan line converge as they cross the tube face, result: one large visible scan line.
If deflection coil angles are set wrong or the projector is not mounted flat it will not be possible to remove the line. To check deflection coil angles check the projector is flat with a spirit level, check the screen is flat with a spirit level, sent horizontal skew to 49, delete convergence settings for that block. Go to convergence and exactly centre red and blue on green using only the middle zone (actually raster shift). Now check the green horizontal line is parallel with the ground and that both red and blue exactly match green. If anything is wrong you have deflection coil angle problems. Correcting this will require all blocks to be deleted and the projector set to mid point in the service menu. At this point also check raster widths at approximately the scan frequency you intend to use (do this on an internal test pattern), this may save you a lot of convergence problems, including instability.
If you bought your projector from us deflection coil angles are definitely right, we do all projectors on an engineers table. If you seem to have a problem make sure the projector is mounted level. If deflection coil angle was set for a ceiling install and the projector is floor mounted there will be some error, and vice versa. |
Kal
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