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tomgilmartin
Joined: 15 Jul 2006
Posts: 41
Location: Buffalo NY area
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| Posted: Wed Oct 08, 2008 12:15 pm Post subject: XG-1351LC Strange line across top of raster |
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Here are 2 screenshots of my XG-1351LC. Setup is 720P from a DirecTV HR21 HD DVR via HDMI through a Monoprice switch to an XG-FULLHD Moome HDMI card in the XG projector. Gamma is at full maximum on the Moome card. The screen is 120".
The first is a test pattern from HDNET, looking very good. For those who must know, the last lines say...
"
8 - if you can read these
9 - last few lines, your display
10 - is better than mine.
"
The second is a shot of a dark scene from "The Empire Strikes Back". The funny pixels are an artifact from the camera, a Nikon Coolpix E995, a 3megapixel (2048x1536) camera. What I am asking about is at upper right if you zoom in a horizontal line is visible, RGB not converged. Look closely and you will see that the line extends all the way across the screen, glinting off the gloss black finish of the screen housing. It's more visible at right because the wall is white. This is the top of the raster as the 16:9 image is shifted up to keep my screen as high as possible. Top blanking is on and adjusted to the edge of the white screen surface. This line seems unaffected by blanking. Anybody have a clue what's up with this damn line? It's distracting and the photo doesn't really do it justice. It's actually worse when projecting an image from the PS3. Is this a "front porch" timing issue?
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kschmit2
Joined: 09 Mar 2006
Posts: 1141
Location: Heidelberg, Germany
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| Posted: Wed Oct 08, 2008 3:06 pm Post subject: |
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Most likely the AKB lines. Turn AKB off and the lines should be gone.
You do not need to have AKB enabled all the time.
Press ADJUST, enter passcode, press INFO, scroll down to p02 and select AKB, hit ENTER, select OFF, hit ENTER
Press END, return to USER MODE, and SAVE if asked to do so.
Remeber to turn on AKB periodically (every 6-12 months or so), save, keep it on for 5-10 minutes, shut PJ down. Power it up again, turn AKB off, save.
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tomgilmartin
Joined: 15 Jul 2006
Posts: 41
Location: Buffalo NY area
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| Posted: Wed Oct 08, 2008 8:06 pm Post subject: |
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OK, what the hell is AKB? Why does it make a line? acronylfinder.com gives it as Automatic Kathode Bias, but that doesn't help much. I have never heard of this in 3 years of playing with a Barco 808 and my NEC XG1351LC.
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Brooklyn
Joined: 17 Sep 2007
Posts: 494
Location: Morgan Hill, CA
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| Posted: Wed Oct 08, 2008 8:10 pm Post subject: |
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AKB helps compensate for tube wear. I believe it adjusts your Kelvin levels automatically. (although someone can correct me here) When it is on, there are usually some lines above the picture. When it is off they are not there. Trying turning it off and see if it helps.
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Elaine Benes
Joined: 25 Apr 2006
Posts: 1416
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| Posted: Thu Oct 09, 2008 12:40 am Post subject: |
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Last edited by Elaine Benes on Thu Oct 09, 2008 12:01 pm; edited 1 time in total
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Satanier
Joined: 25 Aug 2008
Posts: 185
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| Posted: Thu Oct 09, 2008 1:09 am Post subject: |
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If I may interject, I have a related question.
I have an XG as well, and have been curious, how often and for how long should AKB be run?
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kschmit2
Joined: 09 Mar 2006
Posts: 1141
Location: Heidelberg, Germany
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| Posted: Thu Oct 09, 2008 7:26 am Post subject: |
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every couple of month for about 10 minutes as mentioned in my previous post.
Originally posted by Doug:
| dbaisey wrote: |
Just know the NECs and they run AKB in the off position by default and dont need that darn line up to tell it what to do. Every now and then you can balance by turning on for a few minutes (noted in the service manual) but thats about all it needs. Doug |
Axatax explained AKB a bit for the Sony G70, but the operating principle is the same for NEC PG and XG series PJs:
| Axatax wrote: | It's a closed feedback loop. If you look at the block diagrams in the service manual, you'll see there's a control line connected to a pin on each tube, which runs back to the C block, then back to either the B or Y* boards, which in turn signals the PA board to adjust output current for one of the CRT grids. That's *roughtly* how it works.
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kschmit2
Joined: 09 Mar 2006
Posts: 1141
Location: Heidelberg, Germany
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| Posted: Mon Oct 13, 2008 8:01 am Post subject: |
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Found another interesting post about AKB,
| TSE wrote: | Each neck card measures the beam current of each tube while it's line is present. The line is a known value of drive. I'll guess it's 5 or 10%. The projector then sets the cut-off so the line is indeed its 5 or 10% of max beam current. If the measurement is 3% of the expected current then the projector will increase the cut-off until the expected reading is attained. Opposite if the measurement is 15%. The cut-off can be changed with the G-2 or the G-1 or cathode voltage can be changed.
Scott |
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