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Please post experience of JVC HD750/350/550/950 bulb lifetime / lamp brightness drop - Page 5

post #121 of 738
4/5/10 at 9:21pm
And a single chip DLP wouldn`t have a prism. Three chip machines bulb lit use prisms.

My bet is the housing around the bulb gives off some gaseous emissions caused by the intense heat of the bulb and while the emissions do not affect the light output of the bulb very much, they have a tremendous effect on the transmissitivity of the prism. Cleaning the surface of the prism closest to the bulb must substantially improve the transmissitivity.
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post #122 of 738
4/5/10 at 9:36pm
Quote:
Originally Posted by erkq View Post

...This isn't dust...

Agree. Some people have said they think it is some sort of residue that forms from the plastic surrounding the bulb heating up - as if it emits some sort of gases that form a residue. Seems like a viable theory to me.
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post #123 of 738
4/6/10 at 2:42am
Thx for the clarification guys.
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post #124 of 738
4/6/10 at 5:55am
While the cure is easy, it probably will need repeating on a periodic bulb hour time basis. gathering data on this will be difficult because the presence of the residue is not always obvious and the difficulty for many of before and after measurement. THE ISSUE HERE IS is the problem continuous or is it say a one time period emission that ceases after burn in and subsequent cleaning. If it is continual, JVC and perhaps other projector manufacturers need to develop a material fix.

the vast majority of say JVC projectors are not sold to people who can do the cleaning.

Get my drift?
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post #125 of 738
4/6/10 at 6:07am
Quote:
Originally Posted by mark haflich View Post

...THE ISSUE HERE IS is the problem continuous or is it say a one time period emission that ceases after burn in and subsequent cleaning.

Good point. Another possibility is that it has an exponentially declining effect over time. I guess we will know more after another x hundred hours pass from the cleaning point and we can go back and see if the prism is smoked-over again and what before/after light measurements are after the next cleaning. Then again in x hundred hours etc. My guess is that it may be somewhat declining over time yet still have an impact so that periodically cleaning could have benefits.

Quote:


If it is continual, JVC and perhaps other projector manufacturers need to develop a material fix.

I think either way it would be great for the pj manufacturers to develop a fix so the issue doesn't even happen the first place.
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post #126 of 738
4/6/10 at 8:50am
Quote:
Originally Posted by lovingdvd View Post

Agree. Some people have said they think it is some sort of residue that forms from the plastic surrounding the bulb heating up - as if it emits some sort of gases that form a residue. Seems like a viable theory to me.

I agree. It seems like some kind of plastic residue to me.
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post #127 of 738
4/6/10 at 8:32pm
I suspect the residue is acting more as a reflector on the prism than as a mere absorber.
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post #128 of 738
4/7/10 at 1:01pm
Quote:
Originally Posted by lovingdvd View Post

Agree. Some people have said they think it is some sort of residue that forms from the plastic surrounding the bulb heating up - as if it emits some sort of gases that form a residue. Seems like a viable theory to me.

Yes; the hazy film we need to keep cleaning off the inside of our windshields is plastic evaporated from our cars' interior components.
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post #129 of 738
4/7/10 at 3:20pm
Quote:
Originally Posted by noah katz View Post

Yes; the hazy film we need to keep cleaning off the inside of our windshields is plastic evaporated from our cars' interior components.

F'n hell! Really?

(Clasps lungs...)
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post #130 of 738
4/7/10 at 4:15pm
Quote:
Originally Posted by R Harkness View Post

F'n hell! Really?

(Clasps lungs...)

It's not plastic. It's a solvent in the plastic that slowly leaches out. It's what keeps the plastic feeling soft.
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post #131 of 738
4/8/10 at 7:58am
I cleaned my 745 hour HD750 last night. The glass prism did have a noticeable smoked dull hue on the surface. You could easily see it when shining a flashlight on it. I used a dry microfiber cloth and the eraser end of a pencil to get right into the corners of the prism and made it perfectly clean. I also cleaned the bulb and the filter while I was at it.

Lets just say that I do not need a measuring tool to see the after results! I backed my iris down 8 clicks and the image is way brighter than before! With the regained brightness, it is like I have the pop of a new projector!

Cleaning the prism is well worth the effort and is really easy to do! But I do wonder how often one has to clean it?
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post #132 of 738
4/8/10 at 8:17am
Quote:
Originally Posted by shiznit View Post

I cleaned my 745 hour HD750 last night. The glass prism did have a noticeable smoked dull hue on the surface. You could easily see it when shining a flashlight on it. I used a dry microfiber cloth and the eraser end of a pencil to get right into the corners of the prism and made it perfectly clean. I also cleaned the bulb and the filter while I was at it.

Lets just say that I do not need a measuring tool to see the after results! I backed my iris down 8 clicks and the image is way brighter than before! With the regained brightness, it is like I have the pop of a new projector!

Cleaning the prism is well worth the effort and is really easy to do!

Glad you had great results. I picked up an increase of 75% by doing this. Sounds like you had about the same maybe. I too am greatly enjoying the projector again. Its been a few weeks since I did this, yet every time I turn it on it quickly comes back to me how much more vibrant and enjoyable the image is.

Quote:


But I do wonder how often one has to clean it?

That remains to be seen. The good news is that its easy enough to check. I'll check my brightness drop off using my light meter periodically. When it seems to be dropping at a rate I think its faster than normal bulb aging, I'll pull out the lamp and reclean the prism and remeasure. So I guess the short answer is that we'll know over time. My hunch is that the adverse effect lessens over time compared to when the plastic is new, but likely still occurs to a certain extent.
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post #133 of 738
4/8/10 at 8:30am
Checked my prism, HD-350 1900hrs, also had that light dirty coating + extra dirty around the edges used my LENSPEN, dry carbon optic cleaner, to clean.
Thanks to the OP for this, JVC should detail this in their manuals.
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post #134 of 738
4/11/10 at 3:34am
I cleaned my HD350 prism and the glass surface on the lamp itself too.
I used a cotton tip with some pure alcohol and finished both surfaces off with a Hama lens cleaning pen that I also use for my photocamera lenses.

On the lamp itself the glass was visibly dirty. On the prism itself I could not see very well if there was any residue.
I have about 1200 hours on the lamp and was already thinking of replacing it. Now after the cleaning I think it will be good for another 200-300 hours Not only a noticable increase in light output but also I think there is a gain in sharpness.

I am very happy with this excellent trick

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post #135 of 738
4/11/10 at 8:05am
As long as we're posting pics of tools we used to clean the prism... I have to say, the procedure didn't work very well.

Maybe I should have used a variable speed?

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post #136 of 738
4/12/10 at 11:48am
Quote:
Originally Posted by Sherardp View Post

I'm sort of a rookie to this (2nd PJ) and performed the task a few nights ago. I was running my PJ on hi-lamp since I have the pj paired with a larger screen (126" Carada BW). Afterward I could definitely tell I gained lumen output. Very bright so I bumped it back down to normal mode. One thing I did notice was kind of smoke like film on the glass but it easily wiped off.

Well worth the time and effort to clean both. Thanks gents.

One more with numbers, cleaned both on a rs20 with 830 hours on the clock and jumped from 54.5 lux to 95lux. attached the tracking info :



As you can see i 'refound' about 300hours of bulb time, thanks to the brave souls for finding this out. Pity that JVC doesn't tell us this since its on all HD/RS like models they most have known this for years.

Daniel.
LL
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post #137 of 738
4/12/10 at 1:32pm
I agree with comments above that JVC should really make all the benefits of this cleaning business well known, for it greatly increases the performance of their RSxx projectors.

And I can't thank Thebes (posts # 54, 57, 60 above) enough for discovering the French references to this cleaning issue. And also to lovingdvd (post # 61) who verified its dramatic effectiveness and publicized it so well to the rest of us. Of the very many things I've learned in the Forum over the 5 to 6 yrs that I've been participating, this is by far the most important.
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post #138 of 738
4/12/10 at 1:48pm
Quote:
Originally Posted by millerwill View Post

Of the very many things I've learned in the Forum over the 5 to 6 yrs that I've been participating, this is by far the most important.

And no "thank you's" for my past contributions "chew your food 100 chews before swallowing" to improve digestion and brush your teeth up & Down for a "really white smile" recommendations
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post #139 of 738
4/12/10 at 2:46pm
Quote:
Originally Posted by Alan Gouger View Post

And no "thank you's" for my past contributions "chew your food 100 chews before swallowing" to improve digestion and brush your teeth up & Down for a "really white smile" recommendations

Your illuminating comments, Alan, have been to numerous to list.
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post #140 of 738
4/13/10 at 8:30am
Has anybody noticed, when taking out the lamp assembly to do the cleaning, that the glass cover on the lamp assembly is cracked? (Sorry for the cross post, if you are reading the RS20 owners thread, I asked about this a few days ago, but figure non-RS20 owners, who also have the same kind of bulb, may see the query here, but didn't see it there.)

I recently purchase a lightly used RS20, fired it up, saw that it was working apparently correctly (ie, putting out an image, menus operated).

But before mounting it, I decided to clean it (filter, etc) and while checking the lamp housing area for cleanliness, I found that the front of the lamp housing, the glass, was cracked right across the full width of the housing.




full size detail: http://i208.photobucket.com/albums/b.../sale/lamp.jpg

Questions:

1. Is this a danger? It would seem that part of the function of that big piece of glass on on the front of the lamp housing is to protect the rest of the projector, if the lamp itself blows. Or not?

2. Is this a performance problem? IE, is it likely to impact light output, or the ability of the machine to correctly reach its stated specs/contrast ratio?

3. Will this shorten the lamp life itself?

4. Anyone ever seen this before?

I don't think this was due to rough handling, and I don't think this is the seller pulling a fast one.

It would seem it could have been this way for a while without a user knowing it -- perhaps wondering about a drop in performance, but not experiencing a total unit failure. Of course, it may just be luck that this didn't cause a catastrophic failure, yet. I don't know. So far, the advice I've received is "replace immediately" from everyone except one person, who apparently had the same issue.

Any advice or insight based on experience would be appreciated.
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post #141 of 738
4/13/10 at 3:32pm
Cleaned my RS20 and I am blown away at the difference..mine I can honestly say it's twice the light output from before. I must mention the prism itself was dirty and visibly so as I cleaned half of it to compare, the clean part looked new from the non cleaned section..wow. I also cleaned the lamp which was also dirty.

I have 1032 hours on my lamp and I was about to switch it this weekend until I read this thread. A big kudos to everyone that helped.
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post #142 of 738
4/13/10 at 8:35pm
I got a 40% increase in light output with my RS1 by cleaning the glass plate in front of the "lens integrator" (if I read the review from cine4home.com correctly) which is what one looks at in the projector after removing the bulb assembly. That glass didn't look particularly dirty but I cleaned off a fair amount of blackish material that appeared on several q-tips I used and it did look much cleaner afterwards. My projector has around 3000 hours' use, and I've used two lamps, that may explain why I didn't find much film on my second lamp assembly. There's mention of the film on that glass being the result of initial "outgassing" of plastic components within the projector, meaning that filming won't occur after so many - and who knows how many - hours of initial use.

This might apply to many projector makes with internal plastic parts that outgas and cloud optical elements, blocking light transmission. I'm thinking of some reports of a similar phenomenon with color wheels.
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post #143 of 738
4/13/10 at 9:50pm
Quote:
Originally Posted by nathan_h View Post

Has anybody noticed, when taking out the lamp assembly to do the cleaning, that the glass cover on the lamp assembly is cracked? (Sorry for the cross post, if you are reading the RS20 owners thread, I asked about this a few days ago, but figure non-RS20 owners, who also have the same kind of bulb, may see the query here, but didn't see it there.)

I recently purchase a lightly used RS20, fired it up, saw that it was working apparently correctly (ie, putting out an image, menus operated).

But before mounting it, I decided to clean it (filter, etc) and while checking the lamp housing area for cleanliness, I found that the front of the lamp housing, the glass, was cracked right across the full width of the housing.




full size detail: http://i208.photobucket.com/albums/b.../sale/lamp.jpg

Questions:

1. Is this a danger? It would seem that part of the function of that big piece of glass on on the front of the lamp housing is to protect the rest of the projector, if the lamp itself blows. Or not?

2. Is this a performance problem? IE, is it likely to impact light output, or the ability of the machine to correctly reach its stated specs/contrast ratio?

3. Will this shorten the lamp life itself?

4. Anyone ever seen this before?

I don't think this was due to rough handling, and I don't think this is the seller pulling a fast one.

It would seem it could have been this way for a while without a user knowing it -- perhaps wondering about a drop in performance, but not experiencing a total unit failure. Of course, it may just be luck that this didn't cause a catastrophic failure, yet. I don't know. So far, the advice I've received is "replace immediately" from everyone except one person, who apparently had the same issue.

Any advice or insight based on experience would be appreciated.

I don't have answers to you questions, but just wanted to chime in to say that this is not the first I've heard of someone with a cracked glass in the RS20 like you have reported.
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post #144 of 738
4/14/10 at 1:13am
Quote:
Originally Posted by lovingdvd View Post

I don't have answers to you questions, but just wanted to chime in to say that this is not the first I've heard of someone with a cracked glass in the RS20 like you have reported.

Indeed its the top glass (cover), mine is also cracked :

http://www.xs4all.nl/~daniel/ht/bulb_cr.png

I have decided to replace it just to be on the safe side even if its not the real bulb but just the cover it will probably grow and at some point fail. Seems that in some cases jvc is willing to reduce the price on a replacement.

Daniel.
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post #145 of 738
4/14/10 at 8:19am
Quote:
Originally Posted by danielo View Post

Indeed its the top glass (cover), mine is also cracked :

http://www.xs4all.nl/~daniel/ht/bulb_cr.png

I have decided to replace it just to be on the safe side even if its not the real bulb but just the cover it will probably grow and at some point fail. Seems that in some cases jvc is willing to reduce the price on a replacement.

Daniel.

Wouldn't this be a warranty issue? I just bought mine 2 months ago though I haven't checked for the crack yet.
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post #146 of 738
4/14/10 at 9:03am
Quote:
Originally Posted by danielo View Post

Seems that in some cases jvc is willing to reduce the price on a replacement.

Really? I'm curious to know under what circumstances. Though:


Quote:
Originally Posted by erkq View Post

Wouldn't this be a warranty issue?

I suppose it could be a warranty issue, if one finds it within the short warranty period for the bulb.

In my case, I bought the projector from a fellow AVS-er just a week ago, and found it this way. He was still on his original bulb, a bit over 500 hours on it, after about a year of use.

So in my case, not only has the warranty period on the bulb expired (like nine months ago or something) but since I am the second owner, getting warranty service would be complicated (the original owner offered to stand in for me if there is a warranty issue) and I'd only resort to it for a BIG repair situation.

----

So in this circumstance, I think I consider splitting the cost of a replacement with the original owner, but either way, I should probably replace it since it does appear that using the lamp housing this way is like driving a car without a seat belt: no danger, until there is an unusual situation (like the lamp itself blowing and not being contained by the broken housing glass) and then one really wishes one had been more cautious.
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post #147 of 738
4/17/10 at 11:37pm
Big thanks to millerwill who came by and showed me how to do the cleaning. It was much simpler than I imagined and the results were spectacular! Shining a light directly into the prism prior to cleaning revealed a layer of murkiness. I have 460 hours on my bulb, and did measurements both before and after. On low lamp, I got an 80% increase in brightness! On high lamp, 33% increase. With my screen size, I had fully expected to change the bulb every 500 hours, but this handy trick just bought me some extra time. Thanks AVS!
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post #148 of 738
4/21/10 at 1:33pm
interesting thread -
my first PJ and about 550 hrs on my RS25 - noticed I'm using high power more often when I zoom out to 125"
any downside to all this - damage possibility
so basically take out bulb, bulb housing and clean prism bulb shines thru?
my first PJ and have not even changed a bulb before so slightly hesitant
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post #149 of 738
4/21/10 at 1:45pm
I just read about a piece of advice I hadn't seen before that might be of use: Wear latex gloves when doing this (or just when replacing a bulb). The grease from one's hands can harm the optical components, when it gets superheated, causing cracks or more severe structural integrity problems, apparently.
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post #150 of 738
4/21/10 at 2:13pm
Quote:
Originally Posted by nathan_h View Post

I just read about a piece of advice I hadn't seen before that might be of use: Wear latex gloves when doing this (or just when replacing a bulb). The grease from one's hands can harm the optical components, when it gets superheated, causing cracks or more severe structural integrity problems, apparently.

Yes, it's very important to keep finger oils off high temp glass surfaces and gloves may be a good method. Oils cause differential heating and different expansion rates can cause a bulb to fail. The prism should be OK, though you'll want to clean everything off it regardless.
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AVS › AVS Forum › Display Devices › Digital Hi-End Projectors - $3,000+ USD MSRP › Please post experience of JVC HD750/350/550/950 bulb lifetime / lamp brightness drop