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Paul Patience, P.Eng, PMP, LEED AP


After 3 years with my Sony WegaKF42WE620, I found the screen looked splotchy in some areas.
After extensive reading in the various forums, I found many people talking about their various problems.
Some had blue, yellow, pink, or whatever blobs on their screen. Some had what looked like fingerprint smudges on their screen. Others had squiggles and lines.
Some of these problems are due to the LCD matrices growing images within their matrix, but many of the problems seem to be due to the fact that dust is actually collecting on the optical elements.
The LCD Projection TV's have an inherent problem with dust getting into the lense system.


The first approach to these problems is to ensure that the optical elements are free of dust.
In order to do this, a disassembly of the optical driver assembly is necessary.
To perform this work, I highly recommend that you have patience and careful repair practices to ensure that you do not damage your TV set.
The following procedure is not for the faint of heart and applies to a Sony Wega KF 42WE620. Many similar Projection LCD TV's will follow the same procedure.

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If your TV no longer works or something is wrong after attempting the following, DO NOT CONTACT ME.
I am not in the business of TV repair, there are people that get paid for that work.
If you are having trouble understanding what is written below or a procedure I have described,
then you should not attempt this repair yourself.
It is VERY EASY to break these components as they are very delicate and not meant to be serviced by the average consumer.



1) Remove the back lower panel.
2) Remove the front lower panel below the screen area. There are 3 pressure fit snaps that hold this panel in place as well as 2 thumb screws from the back of the TV on either side.
The pressure fit snaps are VERY snug and you need to get your hand behind the cover to unsnap them without breaking or unduly bending the front cover.
Make sure you keep the front cover coming straight out and not twisting it.
3) Remove the lamp from the front of the TV and disconnect the power light circuit card in the front as shown below.

4) Remove the fan and large metal plate from the back of the set and slide out the electronics section as pictured below.

5) To remove the optical assembly, the large black item as shown below, there are 3 screws that can be seen from the back that are down 3 channels of the assembly. You will need an extra long philips screwdriver to get to these. Disconnect the fan connectors and front lamp cover switch connector as shown disconnected below.

6) After pulling out the Optical Assembly, remove the fan on top, pictured below.

7) To clean this fan unit, I cut a diagonal off the end of a ball point pen housing and inserted it into the vacuum as shown in the image below. The image above is the cleaned unit and the image below is the dust after about 1 year since the last time I cleaned this unit. Our house is very clean but you can see that the unit still collects a lot of dust.

8) After removing the lamp fan, also remove the angled plastic top plate above the LCD matrix assembly and the plastic form on top of the optical assembly, this is in the center of the top of the unit as pictured below.

9) The next step is the most delicate, DO NOT FORCE ANYTHING.
10) The 3 ribbon cables in the top centre of the optical assembly connect the 3 red/green/blue LCD matrix units. You can see these ribbons in the picture below.
To disconnect the ribbon cable you must turn up the small brown wings sticking out from under the cable at the connector.
Use a very fine small screwdriver to bring one of the flaps of the brown ribbon holders up. This will release the ribbon and allow it to be easily removed from the socket.
Disconnect all 3 ribbon cables.

11) To remove the LCD matrix, prism and lens assembly, you must remove the 4 black screws from the front of the unit as well as 4 larger silver screws next to the black screws.
The picture below shows the unit removed with arrows on one side showing the back of the holes where you have to remove the screws.
Do not remove the silver screws holding 2 straight metal plates around the front of the large round lense unit.
After removing all 8 screws, the unit can slide out. Tuck the ribbons down before sliding the unit out from the main optical assembly.

12) The next task is to clean both sides of the 3 LCD matrix units as well as the 3 prism faces. The picture below is unfortunately not in focus but shows the areas that need to be cleaned.

Do not try to remove the LCD Matrix units held on by 3 screws each.
You will misalign your TV convergence!

The mounting on the steel plate that connects to the prism plate is very delicate with plastic connectors at the corners.
I almost broke one of them trying to take the LCD matrix off. I recommend taking a cue tip and using a needle nose pliers, pull off some of the cotton swab to make the cue tip thin enough to get between the matrix and the prism. Be careful not to leave any cotton strands behind. You can use a clean cotton t-shirt to clean off the exposed side of the LCD matrix units as well as the rounded lense cover.
DO NOT USE ANY SOLVENTS OR CLEANERS ON THE LENSES or LCD's. There are coatings that can be easily removed with any type of cleaner.

13) Remove the top circuit board from the main optical assembly, there were 3 screws.
14) Remove the flat black plastic cover on top of the main optical assembly unit. The picture below shows the circuit board and cover removed from the main optical assembly.

15) The next step is also a very delicate procedure and must be done with care. The 3 light focusing lenses and 3 colour filters still in the main optical assembly must be cleaned.
Referring to the picture below, the white arrows show 3 small screws holding each colour filter in place. I recommend proceeding with only 1 at a time so that you do not get them mixed up when replacing them. Remove the small screw at the top of the filter and remove the VERY delicate filter unit. Clean both sides with a piece of cotton and set it aside.
The Green filter has an extra filter behind it that must also be removed and cleaned. The yellow arrow below shows the screw and bracket holding that filter in place.

16) After cleaning a filter and before replacing it, use a piece of cotton cloth and clean the round light focusing lense behind the filter as shown by the blue arrow in the picture above.
A more close up, albeit out of focus, picture of this area is shown below.

17) The green arrow in the picture above points to the light tunnel that the lamp bolts against. You should clean this VERY well. I use high grade 100% alcohol to clean this face, not rubbing alcohol as that is mostly water and will not properly clean. I noticed there seemed to be quite a film built up on this face. Anything left behind will be BURNED onto the glass so I highly recommend that this face be VERY clean with absolutely NO fingerprints or anything else left behind.

18) There is another fan on the bottom of the main optical assembly that should be cleaned as best possible.
This fan blows air through the LCD matrix and filter area as shown by the white arrow in the picture above.
A close up of the fan is shown below. You will be able to see this in the cavity behind the blue filter shown on the right above.

19) After cleaning and vacuuming the unit, replace the LCD matrix, prism and lense unit, reconnect the ribbon cables, reinstall the flat black plastic cover.
20) Reinstall the top circuit board as well as the lamp fan and slide the unit back in place. Don't forget to feed the front power light connector back through the front hole.
21) Screw the main optical assembly back onto the TV frame with the 3 screws. You will notice in the picture above step 12 that you can see these 3 screws still attached to the matrix/prism/lense unit.
22) Reconnect the lamp fan electrical connectors, and the front lamp safety switch connector. Put the cable harness back in the holders and clamp downs.
23) Reconnect the front power light connector and slide the unit back in place.
24) Re-install the main lamp in the front and replace the protector cover.
25) Snap the front cover back on and tighten the rear thumb screws.
26) Push the electronic assembly back in place in the TV and replace the PC style fan and metal support plate in the back of the TV.

27) Now turn on your set before you put on the back cover to make sure that your TV works. Hopefully you will not have broken anything or forgotten to reconnect anything and your picture will now look as good as new.
28) If all is well, replace the back cover, sit back and enjoy. If not, time for you to troubleshoot and figure out what you missed.


If you really want to mess with your TV, here is a Service Manual for a similar model, the KF42WE610.
I do not know what all the settings do so this is a user beware warning.
Make sure to record all of your settings before making any changes.

For other manuals, try this site.

If your TV no longer works or something is wrong, DO NOT CONTACT ME.
I am not in the business of TV repair, there are people that get paid for that work.
If you are having trouble understanding what is written above or a procedure I have described,
then you should not have attempted this repair yourself.

Good luck.

Buy me a coffee

If this topic or the whole site has been helpful, please support further development by treating me to a cup of coffee. (click on the coffee mug)

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