Official JVC HD-xxFH97 HD-xxFN97 HD-xxFC97 Owners Thread - Page 222 - AVS Forum
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post #6631 of 6633 Old 09-01-2014, 08:04 PM
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Originally Posted by drlava View Post
Hi everyone. I recently picked up a JVC HD-61FN97. After replacing the lamp, the yellow blobs were noticeable, mostly at the top of the picture. After doing some reading, I decided to look closer to see what the trouble was, expecting to find that same damaged filter, but found this (attached):

<pictures clipped>

The filter is perfect, but there is a burn spot and general haziness INSIDE the first PBS cube. This means that the PBS cube, as manufactured, was defective and the failure cause is not dust buildup because there is no way for dust to find its way into the inner optical surface of the PBS cube.

What is there in the BPS cube? the optical adhesive. Is it possible that JVC or the company that manufactured these optical blocks was using contaminated or defective optical adhesive? We know that the most common failure is the waveplate filter (retarder stack filter) at the entrance of the block which repolarizes blue from horizontal to vertical. Each of these filters is composed of several layers which are also attached to each other with optical adhesive. Let's review photos of a fractino of the failures which happen to be posted online:

<pictures clipped>

One thing becomes clear. The burns always begin at the location of highest optical flux, at the center of the input. The burns start over a 1/4" size area which browns first, then burns. The burns don't begin at speckled areas but evenly over a specific area. This is evidence that what is damaging these filters is not dust, but the filter construction and materials themselves, most likely, the optical adhesive failing in the same way it has failed in my PBS.

What this means is that each of these JVC TVs is at risk of burning and potentially fire in the plastic optical block area due to defective assembly, most likely defective or contaminated optical adhesive. This is not a 'natural aging' of the TVs core, but a widespread defect that existed from the moment they rolled off the assembly line. Not every component, as evidenced by these photos and my experience contains defective optical adhesive, but a significant portion of the TVs do. Mine was manufactured October 2006.

What do you think? Should this be enough to get JVC to do something about it?

You said "The filter is perfect, but there is a burn spot and general haziness INSIDE the first PBS cube."

What I have seen is that the haziness is in fact in the RSF. If you remove it by cutting the little blobs of glue top and bottom, I believe you will see that the cube is fine. The seal between the RSF and the cube is poor too, and there can be a layer of dust between the two.

I doubt if JVC will do much about it at such a late date.

These RSF's don't all do this. I don't know why you can take apart these sets of the same age and find that some of them are still fine and some look like they were tortured with a cigarette butt. Environment may have something to do with it, as a dirty piece of optics will absorb more heat than a clean one. There will also be variances in airflow due to component tolerances.

I've replaced mine with a salvaged unit. All JVC D-ILA tv sets use these same RSF's, they are interchangeable even though they might look a little different.

I have slightly modified the copper plenum cover that sits under the optical engine so a little more air blows over the RSF. I have also changed one of the resistors in the set which controls the regulator that feeds the optical engine fan so that the fan blows just a little faster. I won't know if these steps make any difference for a year or two.

Last edited by ChuckF.; 09-01-2014 at 08:36 PM.
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post #6632 of 6633 Old 09-04-2014, 09:26 PM
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Originally Posted by ChuckF. View Post
You said "The filter is perfect, but there is a burn spot and general haziness INSIDE the first PBS cube."

What I have seen is that the haziness is in fact in the RSF. If you remove it by cutting the little blobs of glue top and bottom, I believe you will see that the cube is fine. The seal between the RSF and the cube is poor too, and there can be a layer of dust between the two.

I doubt if JVC will do much about it at such a late date.

These RSF's don't all do this. I don't know why you can take apart these sets of the same age and find that some of them are still fine and some look like they were tortured with a cigarette butt. Environment may have something to do with it, as a dirty piece of optics will absorb more heat than a clean one. There will also be variances in airflow due to component tolerances.

I've replaced mine with a salvaged unit. All JVC D-ILA tv sets use these same RSF's, they are interchangeable even though they might look a little different.

I have slightly modified the copper plenum cover that sits under the optical engine so a little more air blows over the RSF. I have also changed one of the resistors in the set which controls the regulator that feeds the optical engine fan so that the fan blows just a little faster. I won't know if these steps make any difference for a year or two.
I know the images don't give 3D vision, so I've taken the filter off so you can see:


The spot and hazing really is in the PBS cube.

Take a close look at your burned filters. If you have any that haven't burned, but browned, look very closely and see if the browning is on the front or back, or instead inside the filter.

If you have a light engine that has a good PBS cube, I'd be interested in replacing the blue-off cube in this set.
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Last edited by drlava; 09-04-2014 at 09:35 PM.
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post #6633 of 6633 Old 09-05-2014, 09:43 PM
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Originally Posted by drlava View Post
I know the images don't give 3D vision, so I've taken the filter off so you can see:

<clipped pictures>

The spot and hazing really is in the PBS cube.

Take a close look at your burned filters. If you have any that haven't burned, but browned, look very closely and see if the browning is on the front or back, or instead inside the filter.

If you have a light engine that has a good PBS cube, I'd be interested in replacing the blue-off cube in this set.
I've not seen a defect like that in a JVC D-ILA X-cube, but it's certainly possible. I have seen defects in the X-cube in Sony and Hitachi 3-LCD sets that I suspect are partial fractures of one of the glued joints. That manifests as an inability to get one of the colors to sharply focus.

In my FN the bad RSF first showed up in the picture as a faint yellow cloud high-left and a magenta cloud low-right. The filter only looked a little cloudy, nowhere near the charred spot like some of the bad ones in this thread.

I replaced my 61FN RSF with a better RSF from an older 61Z456, a 720p set, which you can do. The rest of the cube though is quite different in the 1080p set. If you want to replace your 52/61/70FN (or FH, FC, FB) X-cube I believe you need to stick with those codes.

One of these days I want to set up a R, G & B source (LEDs) and some polarizing filters and test the marginal RSF's to see what they look like.
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