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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Sun Aug 31, 2008 10:57 pm Post subject: |
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I remember asking if it was ok to squash the raster on the Sony 1252 to get to 16:9. lol We were all newbies once.
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Sun Aug 31, 2008 11:08 pm Post subject: |
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If the main problem with messed-with XGs is color balance, I wonder if it would be possible to correct it (or most of it) with a detailed gamma transform on an HTPC. There are some tools out there that allow 32 or even 64 point gamma curves per-channel. If you make R, G and B straight ramps and the correct brightness at the top, you should be golden (or white  ). Granted, it'd be a pain to do, and you'd have to use an HTPC - but it might be a way to resurrect an otherwise unusable NEC...
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AnalogRocks
Forum Moderator
Joined: 08 Mar 2006
Posts: 26706
Location: Toronto, Ontario, Canada
TV/Projector: Sony 1252Q, AMPRO 4000G
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| Posted: Sun Aug 31, 2008 11:21 pm Post subject: |
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| perisoft wrote: | | If the main problem with messed-with XGs is color balance, I wonder if it would be possible to correct it (or most of it) with a detailed gamma transform on an HTPC. There are some tools out there that allow 32 or even 64 point gamma curves per-channel. If you make R, G and B straight ramps and the correct brightness at the top, you should be golden (or white ). Granted, it'd be a pain to do, and you'd have to use an HTPC - but it might be a way to resurrect an otherwise unusable NEC... |
One of those twiddled with set's ( is that even a word? Did I just start a new term? ) where some genius has gone in a turned all the pots? That's a PITA idea but sounds like a fun project for someone with allot of time and patience.
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Sun Aug 31, 2008 11:38 pm Post subject: |
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| AnalogRocks wrote: | | perisoft wrote: | | If the main problem with messed-with XGs is color balance, I wonder if it would be possible to correct it (or most of it) with a detailed gamma transform on an HTPC. There are some tools out there that allow 32 or even 64 point gamma curves per-channel. If you make R, G and B straight ramps and the correct brightness at the top, you should be golden (or white ). Granted, it'd be a pain to do, and you'd have to use an HTPC - but it might be a way to resurrect an otherwise unusable NEC... |
One of those twiddled with set's ( is that even a word? Did I just start a new term? ) where some genius has gone in a turned all the pots? That's a PITA idea but sounds like a fun project for someone with allot of time and patience. |
I don't have time, but I apparently have a hell of a lot of patience. If somebody dropped a twiddled-with XG135LC on my doorstep, I'd probably have a look. 
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Mon Sep 01, 2008 12:05 am Post subject: |
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| perisoft wrote: | | If the main problem with messed-with XGs is color balance, I wonder if it would be possible to correct it (or most of it) with a detailed gamma transform on an HTPC. There are some tools out there that allow 32 or even 64 point gamma curves per-channel. If you make R, G and B straight ramps and the correct brightness at the top, you should be golden (or white ). Granted, it'd be a pain to do, and you'd have to use an HTPC - but it might be a way to resurrect an otherwise unusable NEC... |
No, it won't work.
But it's NOT THAT HARD.
And anyway, there really aren't that many fiddled (twiddled ~mod )XGs, most are FINE.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Sep 01, 2008 12:19 am Post subject: |
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I see no reason why you couldn't use an Eye One with Kal's quide to reset these adjustments. Maybe even better then factory. Actually factory adjustments are off after some time has been put on the tubes or a tube change. Just need someone to try it out.
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Mon Sep 01, 2008 12:31 am Post subject: |
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You don't need a colourimeter (handy in the final step but not essential), you need an oscilloscope.
Someone to try it out? Quite a few of us have redone the mechanical white balance on an XG/PG.
But most XG's will not need this.
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Sep 01, 2008 12:44 am Post subject: |
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I agree with your process Mark but what I was referring to is it could probably also be done with a colourimeter. This would give the adjustment ability to those who dont have a scope, service manual, ability to use and understand both or understand electronics at all.
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Mark_A_W
Joined: 15 Mar 2006
Posts: 3068
Location: Sunny Melbourne Australia
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| Posted: Mon Sep 01, 2008 12:54 am Post subject: |
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Ok, but I'm telling you that you can't.
The process is setting a variety of waveforms to specific voltage levels on a scope, based on instructions from the manual.
You barely look at the screen at all..
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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 01, 2008 12:56 am Post subject: |
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| stefuel wrote: | | kal wrote: | | macgyver655 wrote: | | In my opinion, the only people that should be buying used projector's from people they don't know is someone who knows hot to fix it themselves. Other wise it can end up costing you double or triple of what a fully tested one for Curt would cost. |
I would have to agree.
Whenever someone asks "what should I look for?" that means they don't know enough about projectors to buy one like this where all sales are final (unless they're willing to take the risk of course).
Kal |
Oh you guy's are killing me. I need some Depends. 
I wonder what kind of questions I'd dig up if I was to drudge through the AVS archives for some of youz guy's first posts.
Mine was some useless ECP questions. Remember when they were the hot item  |
I remember that time well! And if you search back in the AVS archives you'll get a lot of questions from me for sure. But I realized a few months into reading about CRT projectors that I was over my head so my FIRST crt projector was bought from Curt for that exact reason, so that I had piece of mind.
The hardest thing for someone to know is when they don't know something. That's really why I posted what I did above. If someone has to ask "What should I look for?" they really know know enough to buy a projector sight-unseen from an unknown vendor without some sort of risk. I'm not saying that they shouldn't buy it, I'm just saying it's impossible to teach someone in a post or two for "what to look for". There are simply too many things that an experienced user takes for granted.
The question is very similar to buying a used car. Imagine someone who doesn't know a carborator from a transmission asking in a car forum: "I'm going to go see a used model XYZ car that's for sale, what should I look for?". There are litterally a million things that the person should know if they want to truly make sure the car is ok.
Kal
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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 01, 2008 1:03 am Post subject: |
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| macgyver655 wrote: | | I agree with your process Mark but what I was referring to is it could probably also be done with a colourimeter. This would give the adjustment ability to those who dont have a scope, service manual, ability to use and understand both or understand electronics at all. |
| Mark_A_W wrote: | Ok, but I'm telling you that you can't.
The process is setting a variety of waveforms to specific voltage levels on a scope, based on instructions from the manual.
You barely look at the screen at all.. |
Mark is 100% right.
The white balance settings on an XG have actually nothing to do with greyscale. It goes much deeper than that.
It's about how the projector productes colours & white levels. As he stated it's about getting the projector to perform within a correct dynamic range with a correct balance. Requires a 'scope, a Japanese to English dictionary and a deep understanding of video signals. I'm making this up a bit but for example, they'll tell you you to "display a 15.6Khz SMPTE pattern and adjust pot G602 until pedistal measures 0.2Vpp". That's it. You need to know what pedistal means, you need to know what SMPTE pattern means, and so on. It's meant for video technicians. If that previous sentence together with a screenshot of the 'scope signal isn't enough for someone to understand what to do then they're not going to be able to adjust those pots correctly. There is zero hand-holding here.
You couldn't adjust in an HTPC either. It goes well below that. It's all about getting the XG to display a fundamentally correctly balanced image. As Mark stated you never even look at the screen. You spend all your time looking at the waveforms on the 'scope.
I spent a couple of days trying to get a 'twiddled' XG to work correctly using a 'scope and the service manual but gave up because (a) my 'scope is older and noisy, and (b) I'm not a video technician so some of the terms (even after searching) got to me.
Kal
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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 01, 2008 1:13 am Post subject: |
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Ok, so here's an example taking directly from the XG service manual for those that still wondering if they'd be able to perform the adjustments:
That's it. That's all you get. This partial procedure is not for the white balance pot adjustments but it shows you something similar (how to properly adjust pots VR703 and VR812 after they've been messed with or you've replaced this card).
So hopefully you can all see that following these sorts of instructions and succeeding is not something that everyone can perform. Just like most service manuals, they're meant for service technicians.
Kal
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Last edited by kal on Mon Sep 01, 2008 1:14 am; edited 1 time in total
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stefuel
Joined: 07 Mar 2006
Posts: 3353
Location: Green Harbor MA USA
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| Posted: Mon Sep 01, 2008 1:14 am Post subject: |
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| Mark_A_W wrote: | You don't need a colourimeter (handy in the final step but not essential), you need an oscilloscope.
Someone to try it out? Quite a few of us have redone the mechanical white balance on an XG/PG.
But most XG's will not need this. |
It ain't no thing. All you need is a scope, DMM, manual, 2-3 pots of coffee, some uppers, some downers, a hooker or two and be able to follow exacting instructons with hookers in da house
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A Barco is only a AmPro with training wheels
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Sep 01, 2008 1:18 am Post subject: |
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Thats like saying the only way to adjust G2 is with a scope. And thats not true. Also I just read the entire adjustment procedure on the PG extra and each section after a scope check refers to measure color temperature to make sure of certain settings and if not make adjustments to correct color temp. This would then change the just previous made scope setting. So the scope is not the final settings which could also indicate color balance supersedes scope settings. Also voltage and waveform settings dont allow for tube wear or lower tube emission which is why color balance comes into affect.
Buts thats as far as I will comment on this. No offense anywhere, just a suggestion.
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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 01, 2008 1:23 am Post subject: |
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| macgyver655 wrote: | | Thats like saying the only way to adjust G2 is with a scope. And thats not true. Also I just read the entire adjustment procedure on the PG extra and each section after a scope check refers to measure color temperature to make sure of certain settings and if not make adjustments to correct color temp. This would then change the just previous made scope setting. So the scope is not the final settings which could also indicate color balance supersedes scope settings. Also voltage and waveform settings dont allow for tube wear or lower tube emission which is why color balance comes into affect. |
Not sure who this comment is directed at, but as Mark stated, to adjust he white balance pots correctly on an XG, you need a 'scope. There's no other way. We're not taking about adjusting G2. Go read the XG service manual if you don't believe us. I really wish there was an easier way but there isn't.
Kal
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macgyver655
Joined: 22 Aug 2007
Posts: 8508
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| Posted: Mon Sep 01, 2008 1:26 am Post subject: |
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Which XG manual are you reading from so I can read from that one. I have all 3 manuals.
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Mon Sep 01, 2008 1:28 am Post subject: |
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OK, here's what I don't get: The PJ needs to take inputs (on each channel) going 10%, 20%, 30%, etc, and project with the same relative brightness - so you see 10%, 20%...
The PJ will ALWAYS project some curve along there. If things are totally hosed it might even go 10%, 30%, 20%... but it'll end up making some kind of ramp from 0 to 100% for each primary.
If you put those ramps through a lookup table so every point in maps to the right point out, it just WILL work. It cannot fail to work in any way I can see. Yes, the white could be totally screwed up, but again, change the top end so that R, G, and B are the same perceived brightness, and there's your white.
If I'm missing something here, what is it? If somehow these adjustments mean that you get a TOTALLY nutty curve, like 0% 100% 0% 100% 50% 50% 0% 0% 0% instead of 0% 10% 20% 30%... ok, I could see not being able to compensate for that. But based on what I'm seeing here that's not the case... so why won't very detailed level fixes work?
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kal
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kal
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| Posted: Mon Sep 01, 2008 1:45 am Post subject: |
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| perisoft wrote: | OK, here's what I don't get: The PJ needs to take inputs (on each channel) going 10%, 20%, 30%, etc, and project with the same relative brightness - so you see 10%, 20%...
The PJ will ALWAYS project some curve along there. If things are totally hosed it might even go 10%, 30%, 20%... but it'll end up making some kind of ramp from 0 to 100% for each primary.
If you put those ramps through a lookup table so every point in maps to the right point out, it just WILL work. It cannot fail to work in any way I can see. Yes, the white could be totally screwed up, but again, change the top end so that R, G, and B are the same perceived brightness, and there's your white.
If I'm missing something here, what is it? If somehow these adjustments mean that you get a TOTALLY nutty curve, like 0% 100% 0% 100% 50% 50% 0% 0% 0% instead of 0% 10% 20% 30%... ok, I could see not being able to compensate for that. But based on what I'm seeing here that's not the case... so why won't very detailed level fixes work? |
An input curve only works if you have a full range to work with. If the white balance pots are messed certain settings may only work above (say) 50 IRE so you have half the scale that can't be adjusted for.
Kal
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perisoft
Joined: 29 Aug 2007
Posts: 2920
Location: Ithaca, NY
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| Posted: Mon Sep 01, 2008 1:51 am Post subject: |
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| kal wrote: |
An input curve only works if you have a full range to work with. If the white balance pots are messed certain settings may only work above (say) 50 IRE so you have half the scale that can't be adjusted for.
Kal |
Yeah, that would make for a kind of dim projector (or pretty awful black levels). On the other hand, the tubes would last forever...
Still, it would seem that an input curve could get you the last 30% or even 40% of the way there - certainly better than having an XG doorstop.
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