Please post experience of JVC HD750/350/550/950 bulb lifetime / lamp brightness drop - Page 13 - AVS Forum
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post #361 of 738 Old 10-26-2010, 10:58 AM
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Originally Posted by Bches View Post

Makes sense -- It's hard for me to understand how increasing brightness would not change the contrast of a projected image. Increasing brightness would not make blacks blacker, but it would increase highlights etc.

It's all linear. If increasing brightness increased just the bright parts of the scene, we would all be in hog heaven with super-bright super-high c/r projectors. Unfortunately, the increase in brightness is linear across the whole IRE range. Making it non-linear is quite a trick that projector manufacturers are always looking to improve.
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post #362 of 738 Old 10-26-2010, 04:56 PM
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In other words: It also makes blacks less black.

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post #363 of 738 Old 10-26-2010, 07:04 PM
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Originally Posted by nathan_h View Post

In other words: It also makes blacks less black.

I tip my hat to a MOFW. Very succinct compared to my ramblings.
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post #364 of 738 Old 10-27-2010, 06:51 AM
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You guys do watch movies, right?

"What we do in life echoes in eternity." General Maximus Decimus Meridius
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post #365 of 738 Old 10-27-2010, 12:18 PM
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You guys do watch movies, right?

Who the heck watches movies? Test patterns baby, test patterns.
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post #366 of 738 Old 10-27-2010, 02:06 PM
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Originally Posted by lovingdvd View Post

Yes, I tried the lamp cleaning and had excellent results.

At first When I opened it up I was a bit disappointed to find that the socket didn't look that dirty at all. A bit "smoked over" looking (sort of like as shown in someones pictures in one of the articles above, but not quite as visible) but no real visible dust. I used a non-alcoholic environmentally safe glass cleaner on a microfiber lens cleaning cloth.

The cloth did not appear dirty or dusty after cleaning. Likewise the bulb was pretty clean too. But I wiped it down as well. A very small amount of residue there, I think mainly coming from the edges and not the glass itself. I let everything dry for a while before turning the pj back on.

When I fired the pj back up it looked noticeable brighter. When I walked in front of the lens I had to squint which I haven't noticed myself doing at all for a long time.

I then took out my meter and was stunned - it measured 89.1 lux, which was a whopping 75% increase!

What environments are the projectors being used in where a dramatic increase in brightness is seen after cleaning?

Jeff
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post #367 of 738 Old 10-27-2010, 02:08 PM
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Originally Posted by pepar View Post

What environments are the projectors being used in where a dramatic increase in brightness is seen after cleaning?

Jeff

The operating theory so far is that it is some sort of gas/resin and not smoke or dust/dirt, if that's what you are wondering.
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post #368 of 738 Old 10-27-2010, 02:17 PM
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Originally Posted by lovingdvd View Post

The operating theory so far is that it is some sort of gas/resin and not smoke or dust/dirt, if that's what you are wondering.

Precisely. So it's thought to be something that off-gassed from inside the projector?

Jeff
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post #369 of 738 Old 10-27-2010, 03:26 PM
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Originally Posted by pepar View Post

Precisely. So it's thought to be something that off-gassed from inside the projector?

Jeff

....I suspect this is what is behind the poor contrast being previously blamed on Prismasonic anamorphic lens.

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post #370 of 738 Old 10-27-2010, 03:32 PM
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Originally Posted by pepar View Post

Precisely. So it's thought to be something that off-gassed from inside the projector?

Jeff

Yes, mine's smoke free, dust free, and lives in a very clean little 4' x 5.5' projection booth with a door. Yet I had a very good result from cleaning (posted a while back).
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post #371 of 738 Old 10-27-2010, 03:34 PM
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Originally Posted by erkq View Post

It's all linear. If increasing brightness increased just the bright parts of the scene, we would all be in hog heaven with super-bright super-high c/r projectors. Unfortunately, the increase in brightness is linear across the whole IRE range. Making it non-linear is quite a trick that projector manufacturers are always looking to improve.

My experience shows the contrast improves remarkably after cleaning. How? The haze acts as a diffuser, scattering light in all the wrong directions just as the light beam leaves the lamp housing and enters the projector optics. Light scattering kills contrast.

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post #372 of 738 Old 10-27-2010, 03:39 PM
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Our guess is off gased from some part or parts holding the lamp or otherwise part of the lamp and cage assembly. Something directly exposed to the lamp heat. I think the cleaning of the prism should be considered a routine maintenance step say once evry 500 hours. It can`t hurt and it might help. Some may be reluctant to do it but its really really easy and it idiot proof providing the projector is cool and you unplug it.

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post #373 of 738 Old 10-27-2010, 03:43 PM
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Quote:
Originally Posted by Jedi View Post

My experience shows the contrast improves remarkably after cleaning. How? The haze acts as a diffuser, scattering light in all the wrong directions just as the light beam leaves the lamp housing and enters the projector optics. Light scattering kills contrast.

I think that's a very good point. It wouldn't affect on/off but may affect (Are you watching Mark? Did I get that right?) intra-scene contrast. Projector optics hate light scatter.
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post #374 of 738 Old 10-27-2010, 04:05 PM
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Originally Posted by mark haflich View Post

....its really really easy and it idiot proof.

....I sprayed Windex in mine and now it won't work.

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post #375 of 738 Old 10-27-2010, 04:11 PM
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Originally Posted by Jedi View Post

....I sprayed Windex in mine and now it won't work.

Ok, almost idiot proof. I suspected there was bit more grime on mine that I could not see, so I used a dremel with the grinding wheel attachment. I think I lost a little sharpness...
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post #376 of 738 Old 10-27-2010, 04:16 PM
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Originally Posted by Jedi View Post

....I sprayed Windex in mine and now it won't work.

That just means there is a level beyond idiocy. But, really... it's still idiot proof.

Reminds me of helping an executive secretary at LS&Co. (back in the 80's) whose keyboard stopped working when she hit a key "somewhere up in the numeric keypad area." I prompted further and she said, "Yeah... I was wiping the coffee off and I hit some key up there and now it won't work." Ayayay...
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post #377 of 738 Old 10-27-2010, 04:56 PM
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I think its just blocking some of the light that would otherwise go through the prism. Nothing fancy, just the grime is reducing the overall light transmissivity of the prism.

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post #378 of 738 Old 10-27-2010, 05:36 PM
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from reading the thread saw several references to the process being idiot proof. Then did several searches for a lens cleaning process - nothing comes up. can someone point me to it?

Thanks!
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post #379 of 738 Old 10-27-2010, 05:50 PM
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First of all, this procedure does not involve cleaning the lens. The procedure for cleaning the prism can be found n this thread. It is easier for you to find then for me to reiterate it.

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post #380 of 738 Old 10-27-2010, 10:14 PM
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It will take me a day to post more complete data and pics of what we did, but center screen without Panamorph went from 44.3 lx to 103.4 lx post cleaning, and from 33.6 lx with lens to 75.8 lx post cleaning and lining the inside of the Panamorph with blackout felt.

The "prism-y" thingy just in front of the lamp had a thick haze over it. I have pics of that I will post.

I started this on the "Official" thread and will at least post a link there to what I post here. EVERY projector owner should at least be aware of this! The difference in the picture is NOT subtle. Sunday eve we will revisit the calibration which was done last Sunday.

Jeff
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post #381 of 738 Old 10-27-2010, 10:53 PM
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Quote:
Originally Posted by pepar View Post

It will take me a day to post more complete data and pics of what we did, but center screen without Panamorph went from 44.3 lx to 103.4 lx post cleaning, and from 33.6 lx with lens to 75.8 lx post cleaning and lining the inside of the Panamorph with blackout felt.

The "prism-y" thingy just in front of the lamp had a thick haze over it. I have pics of that I will post.

I started this on the "Official" thread and will at least post a link there to what I post here. EVERY projector owner should at least be aware of this! The difference in the picture is NOT subtle. Sunday eve we will revisit the calibration which was done last Sunday.

Jeff

Glad you had fantastic results. I did too. Oddly some folks report no benefit at all. One theory is that those folks may be using the newer bulb that supposedly replaced the original bulb used in the earlier runs of these projectors.
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post #382 of 738 Old 10-27-2010, 10:54 PM
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Originally Posted by pepar View Post

Precisely. So it's thought to be something that off-gassed from inside the projector?

Jeff

Yes. If you are interested in the details it was discussed in this thread several pages back.
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post #383 of 738 Old 10-28-2010, 07:26 AM
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Originally Posted by pepar View Post

EVERY projector owner should at least be aware of this! The difference in the picture is NOT subtle.

Jeff

I was among those at Jeff's last night. There were 2 incredible moments. One was when the thick haze was wiped off the prism and revealed just how restrictive the haze was, the second was when we saw the difference in light output and verified via light meter. After these pictures are posted, I predict projectors will be falling from the sky. And if they don't, they should!

Dr V
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post #384 of 738 Old 10-28-2010, 07:51 AM
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Seeing how it's free to check and clean, and could produce a dramatic improvement, it seems like a no-brainer.

I worked on creating images of the before and after measurements, and I have them of the cleaning process, but won't be able to post everything until this afternoon. I'll apply some math to everything for a summation.

Here's another teaser ... after cleaning without lens measurements increased from 107% to 183%. The biggest increase occurred in the lower right corner which previously had the biggest variation (negative) from the center of the screen. Cleaning the "prism" made the output across the image considerably more uniform .. as it the haze was not uniform and caused the variations.

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post #385 of 738 Old 10-28-2010, 08:25 AM
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For months I have told people to do this and I wasn`t the first to endorse this and learned about from a call from lovingdvd, who did the Nike bit on me, Just Do It for my customers. Hell I don`t even own a JVC myself though I have tested, run in, and set up many RS35 though. It will take more time to read about people doing it and their results and tests than it would take to do it. And one gains nothing from all that reading once the difficult, complex, and extremely dangerous procedural steps are mastered.

Huh. What`s he saying about difficult, complex, and dang.....? Gotcha.


Let me simplify. People will change a bulb on their own. The bulb changing procedure is in the manual.

Follow the procedure therein but don`t change the bulb, don`t reset the bulb hour meter, just clean the glass window (wipe the whole surface gently) you see when you take the bulb out with a piece of micro fiber lens cleaning cloth. That`s it.

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post #386 of 738 Old 10-28-2010, 09:35 AM
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Quote:
Originally Posted by pepar View Post

It will take me a day to post more complete data and pics of what we did, but center screen without Panamorph went from 44.3 lx to 103.4 lx post cleaning, and from 33.6 lx with lens to 75.8 lx post cleaning and lining the inside of the Panamorph with blackout felt.

The "prism-y" thingy just in front of the lamp had a thick haze over it. I have pics of that I will post.

I started this on the "Official" thread and will at least post a link there to what I post here. EVERY projector owner should at least be aware of this! The difference in the picture is NOT subtle. Sunday eve we will revisit the calibration which was done last Sunday.

Jeff

I also got more than a factor of 2x increase in lumens upon my first cleaning. Of the reports I've seen, I think we two have seen the greatest increase. Neat!
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post #387 of 738 Old 10-28-2010, 10:49 AM
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And here's another bizarre twist to the story... Out of those of us who had great results (say 1.5x brightness improvement or more) from an initial cleaning, only some of us reported improvement from a second cleaning hundreds of bulb hours later.

For instance at around 700 hours or so (can't quite recall but its probably somewhere in this thread) I had a huge improvement in brightness. But when I tried again a couple hundred hours later there was NO measured improvement whatsoever. Whereas some have repeated the cleaning and got improvements a second time. Weird.
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post #388 of 738 Old 10-28-2010, 10:53 AM
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Originally Posted by lovingdvd View Post

And here's another bizarre twist to the story... Out of those of us who had great results (say 1.5x brightness improvement or more) from an initial cleaning, only some of us reported improvement from a second cleaning hundreds of bulb hours later.

For instance at around 700 hours or so (can't quite recall but its probably somewhere in this thread) I had a huge improvement in brightness. But when I tried again a couple hundred hours later there was NO measured improvement whatsoever. Whereas some have repeated the cleaning and got improvements a second time. Weird.

I got some improvement the second time--don't remember how much offhand, but did post it above--but not nearly so much as the first time. (And thanks still again for initially beating the drum for this process!)
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post #389 of 738 Old 10-28-2010, 11:04 AM
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Originally Posted by lovingdvd View Post

And here's another bizarre twist to the story... Out of those of us who had great results (say 1.5x brightness improvement or more) from an initial cleaning, only some of us reported improvement from a second cleaning hundreds of bulb hours later.

Perhaps it's due to differences between resin batches used to make the plastic parts inside the pj.

Outgassing plastic is my hypothesis, like the film that forms on the inside of windshields from the interior parts outgassing.

Noah
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post #390 of 738 Old 10-28-2010, 11:10 AM
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I got some improvement the second time--don't remember how much offhand, but did post it above--but not nearly so much as the first time. (And thanks still again for initially beating the drum for this process!)

I was just surprised to see that I got ZERO improvement from a second cleaning. Measured identically before and after. Kinda was bummed. It's like getting a free lunch. That being said, I hope JVC has identified this issue and the new line will not be subject to whatever it is that causes this.
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