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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Wed Jan 04, 2017 3:10 am Post subject: |
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I'm having the oddest problem and it's not making any logical sense!
Problem: In my own Ultra in my theater room, I have new LUG tubes installed.
The green tube is problematic. It focuses perfectly in the central zone. On the outer zones it doesn't focus properly.
I can push the outer zones into focus but only at the expense of getting central zone focus.
This problem appears even when the astig, convergence, and focus coils are UNPLUGGED.
I changed out the focus board, and swapped the LVPS as well.
No change.
So...I have a test chassis in the garage. I installed the green tube assembly in question in the test chassis, and determined that
the focus yoke was not very good. So I swapped it out for another focus yoke, and then that ran perfectly on the test unit. Sharp from corner to corner, even at high contrast.
I moved the tested, proven assembly back to my projector, did a quick magnetic alignment....
AND THE PROBLEM IS EXACTLY THE SAME.
I have one more thing to check, and that's the neck card. I can't imagine why a neck card could be affecting focus in the outer zones only, but I'm going to give it a shot!
If this doesn't fix it then, screw it, I'm going to pull the Ultra down and flip a coin. If it comes up heads I'm going to install my test chassis. If it comes up tails I'M PUTTING IN A G90.
This is like changing a flat tire and putting a brand new, freshly aired up tire on your car and as soon as you drop it off the jack, it's flat again. Jack the car back up again and the tire's at its intended pressure.
I'd be wondering if there was an extreme electronic noise issue at stake here but if that were the case, then it'd be just as noisy in the central area than it is on the edges.
Maybe the VIM is doing something screwy.....
I have a JVC RS45 D-ILA projector. I could always just make that my main PJ and sell off everything else, if I get angry enough.
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gregstv
Joined: 27 Aug 2007 Posts: 628 Location: Australia
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Link Posted: Wed Jan 04, 2017 4:33 am Post subject: |
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Do you have a degausing wond. May be try degausing the projector. This was a common problem with crt televisions. Not sure if projectors suffer from the same issue. They won't have the purity issue but it may affect the focus.
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Wed Jan 04, 2017 5:04 am Post subject: |
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I don't think it's that. There's no evidence of any magnetic problems, and I did check for that.
I may end up making a degaussing wand just in case, though.
I'm starting to wonder if it's a crosstalk issue on the VIM or maybe an issue with a neck card.
With a lot of work on astig and focus I was able to tame the issue to some extent but that masks the problem,
it doesn't fix the root problem. Really it's going to bug me until I get to the bottom of it and fix it
I did notice something which indicates it may be a crosstalk problem. You may have noticed that if you mute the red and blue tubes
on a Marquee and then bring up the menus, you'll still see traces of the menu page if you're looking directly into the red or blue lenses. (This actually applies to all colors.) When going through some adjustment, green should have been muted and it was, while I worked on the red tube, but the convergence grid that was displayed was visible when looking into the green lens, and significantly, it was brighter around the edges than it should have been. Bright at pretty much exactly the same places where it's not well focused.
So, though I can't explain the mechanism by which this possible crosstalk is occurring, it really does kind of look like a crosstalk issue.
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cmjohnson
Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s
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Link Posted: Wed Jan 04, 2017 5:38 am Post subject: |
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OK, I have confirmed that there's a very, very weird crosstalk problem going on here.
Please see if YOUR Marquee does this.
Test conditions: Display the convergence grid.
Video mute any two tubes (Press COLOR then 1, 2, 3, 4, 5, or 6.) and the look into one of the muted (dark) tubes
while ramping contrast up to 100.
You should see nothing in the muted tube. Of course, the active tube will have a bright grid showing. Back the contrast back down to normal levels and change which tubes are muted. Repeat this process for all tubes.
When I do it on this machine as described, when I'm looking at the muted green tube and ramp up the contrast, the image starts to be drawn on the green tube starting from the outer edge. The higher the contrast the closer to the center the now VISIBLE grid gets. It never gets close to the center but it does get in some distance from the edges.
The image shows up in a ring-shaped area. It starts at the outer edges and fills in more toward the center at higher contrast.
It seems to also match up exactly with the loss of focus as seen on the green raster. When it gets brighter, the out of focus area starts at the edge of the screen and grows inward with higher contrast settings.
This may also be an issue with the video blanking system. It may be on a neck card. It may not. I'll swap out some neck cards and see what happens next. If it's not the neck card, then the chassis has to come down. It's too close to the back wall for
me to be able to swap out the VIM with the unit on the ceiling.
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