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opv
Joined: 18 May 2010
Posts: 202
Location: Emek Hefer,Israel
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| Posted: Wed Jun 13, 2012 8:56 am Post subject: BG1209s horizontal linearity issue |
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Hi,
I have a horizontal linearity problem on my BG1209s.
In the geometry pattern, with the 4 small circles and one bug circle in the middle, the circles on the right side of the screen are ~10% wider than the ones on the left.
I tried adjusting P1 pot on the horizontal deflection, but it only makes the left circles narrower.
Any ideas?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Jun 13, 2012 1:17 pm Post subject: |
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You may be able to get rid of some of it with a convergence on green board. (COG), or by replacing the H deflection board. Some Barcos had an optional H linearity board, but I've tried twice now to put one into a set that didn't have it, and they didn't work for some reason.
I've got COG boards for $150, H deflection for $50 plus shipping.
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opv
Joined: 18 May 2010
Posts: 202
Location: Emek Hefer,Israel
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| Posted: Wed Jun 13, 2012 1:26 pm Post subject: |
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I had a COG board in my previous BG808s, it caused a lot of video noise.
Do you that a problem in the H deflection board is causing this problem?
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Curt Palme
CRT Tech
Joined: 08 Mar 2006
Posts: 24396
Location: Langley, BC
TV/Projector: All of them!
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| Posted: Wed Jun 13, 2012 1:58 pm Post subject: |
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THat's where the problem should be. I have not had issues with a COG causing video noise, every planetarium I deal with has them installed, but maybe they do?
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opv
Joined: 18 May 2010
Posts: 202
Location: Emek Hefer,Israel
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| Posted: Thu Jun 21, 2012 6:13 am Post subject: |
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CAn the source cause such a problem? maybe due to small porches maybe?
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jask
Joined: 17 Mar 2006
Posts: 10187
Location: kamloops BC
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| Posted: Thu Jun 21, 2012 7:36 am Post subject: |
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Have you confirmed that your projector to screen geometry is correct?
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Ile
Joined: 09 Mar 2006
Posts: 1491
Location: Jyväskylä, Finland
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| Posted: Thu Jun 21, 2012 8:04 am Post subject: |
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I think it's possible that too small porches can cause this, but in that case problem should chance to left when you adjust Hphase to left.
What resolution you are using and is your projector in high freq mode? (green led at Hdef sub board)
If you are running around 60-75 kHz and projector is not in high freq mode, switching point can be adjusted by P1 at vertical deflection board. High freq mode should work better for example 1080p with limited porches.
Then you have also other ways for for Hlinearity than just Hdef P1. Hdef boards linearity coils core (15kHz) and P1(18kHz) are used for low freq mode adjustment, but should also have some effect for high freq mode. Then there is P64 at Hdef sub board for high freq mode Hlinearity adjustment.
I have also found out that raster width coils could have some effect to Hlinearity, so tweaking green width coil might also help.
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opv
Joined: 18 May 2010
Posts: 202
Location: Emek Hefer,Israel
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| Posted: Thu Jun 21, 2012 9:54 am Post subject: |
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jask,
The PJ to screen geometry is OK, but not perfect. however, I did try to tilt the screen to see if the problem goes away. I have to use one big tilt to even get close to the amount of mismatch I have.
Ile,
I working at 1080P @50Hz. low freq mode. using high frequency mode causes ringing and jail bars that I simply can't accept.
the linearity coil P1 doesn't solve the problem. it can only make the left side even narrower.
The raster width coils are a good direction.
Since I don't have a VP and the picture I got at 1080P@50Hz, was to small, I had to max out the master width coil.
This might be the reason for the linearity problem I have.
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