Raster Bowing on XBR800 - AVS Forum
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post #1 of 11 Old 06-01-2011, 06:08 AM - Thread Starter
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As the attached pictures show, I've got quite severe bowing on the lower left side of the screen that isn't mirrored on the right side (there is some but not nearly as much) and I can't seem to correct it with the service menu adjustments. Is this one of those things that can only be fixed with magnets, or is there something I'm missing that I can tweak to fix this?

There's also some pincushion problems at the top and bottom (not really noticeable in the pictures as I hadn't reduced the VSIZ enough). I can only seem to get either the top OR bottom straight-ish, using VCEN and VPIN, but that doesn't really notice as much in normal use as the side bowing does.





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post #2 of 11 Old 06-10-2011, 09:43 PM
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Alot of that should be fixable via the geometry controls in the SM. It can be a little tricky tho since many of those controls interact.

You may also find that fixing the geo for one signal messes up the geo for another (a problem I don't have to deal with since I only use 1080i on my TV).

I'll look thru the notes on my 34XBR800 tho and see if I can give you any tips. Try also running a search on likely SM codes here. That may bring up some tips/advice as well.

If you really wanna get things straight as possible, a ruler will help (no joke).

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post #3 of 11 Old 06-11-2011, 01:03 PM
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post #4 of 11 Old 06-11-2011, 02:22 PM - Thread Starter
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Thanks ADU. I certainly haven't been able to find any SM geometry controls that are able to straighten out the left-hand side of the screen.
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post #5 of 11 Old 06-17-2011, 06:52 PM
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Sorry for the delay. Got stuck in a wormhole there for a bit.

I would start with VBOW and/or LBOW in category 2170D-2 in the SM.

If you can't get the sides of the screen pretty straight with one or both of those controls, then try to make the distortion as symmetrical as possible with VBOW and LBOW, so both sides are bowing slightly outward, or slightly inward. Then you can probably fix the remaining bowing with PIN, or possibly MPIN. It's been awhile since I tinkered with the geo on my 34XBR800, but I believe PIN is the main pincushion adjustment for the sides of the screen (which effects the corners most), and MPIN adjusts the pincushion effect more in-between the corners on the sides of the screen.

Bear in mind that most controls in the SM are context-sensitive, and store more than one value depending for example on the signal, zoom mode, picture mode, etc. So write down all the original values for these controls before you start changing them.

VBOW and LBOW appear to be "global" controls (ie, they only store one setting for all modes on my TV). PIN and MPIN appear to store two settings, one for the WIDE ZOOM mode on the TV, and another setting for everything else. It's possible things might work a little differently though on your TV because your 36XBR800 is a 4:3 set and my 34XBR800 is 16:9.

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post #6 of 11 Old 06-17-2011, 08:39 PM
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You might try this...

Set VBOW to 31. Then adjust LBOW (starting around 31) until the sides are symmetrical.

Might work, or might not on your TV.

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post #7 of 11 Old 06-18-2011, 07:10 AM - Thread Starter
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Cheers, I'll try all that and let you know how I get on.

My 36XBR800 is a 16:9 set but I never use anything other than FULL mode anyway, as it's only used with my PC and consoles, which lock it in that mode.
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post #8 of 11 Old 06-18-2011, 04:29 PM
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That may be the same tube as on my "34-inch" set then. (I think stuff gets measured a little differently here.)

I tried the above controls out on my TV, and I think VBOW and/or LBOW are the controls you're probably lookin for to fix the bowing on the left side of the screen. You may be able to fix the issue with just VBOW alone, because the effect of LBOW is more subtle.

On my TV, VBOW=31 and LBOW=40 (hence the previous suggestion). I've tweaked these and many of the other geo controls on my TV though, so there's a good chance my settings won't work on yours.

A couple patterns that may help you see and correct the distortion a little more easily (sorry I don't have any PAL format handy at the moment).

Grid sized for 2.5% Overscan...



Grid sized for 5% Overscan...


LL
LL

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post #9 of 11 Old 06-18-2011, 04:40 PM
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It looks like the raster on your set is slightly tilted as well. There should be a TILT control in the regular USER menus to tweak that. (On my TV the control is under SETUP.) Or, if you need finer control (or prefer to leave the User Menu Tilt control at 0), I believe 2170D-1 NSCO can be used to adjust that as well.

You can probably also fix the slight upward bow on the top and bottom of the screen with 2170D-1 VCEN.

Both of the above controls (2170D-1 NSCO & VCEN) are global on my TV, and only store one setting each. Just be sure to write down all the original settings before making changes.

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post #10 of 11 Old 06-21-2011, 12:32 PM
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I think that VCEN has a nasty habit of shifting the position of the image vertically, so fixing that slight upward bow may requiring tweaking a couple other controls as well. If you want some ideas on how to go about that, just say so.

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post #11 of 11 Old 06-25-2011, 03:49 PM - Thread Starter
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Thanks for all the tips ADU. I just haven't had a chance to tweak the set properly yet, although I think I've improved it somewhat with LBOW/VBOW. I think you were right about the TILT as well, as adjusting that seemed to help.

I'll post again when I've managed to have a real go at tweaking it
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