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How to replace the Laservue L75-A91 TI 1910-6143W Chip

post #1 of 24
Thread Starter 
I purchased my Laservue L75-A91 on 5/31/2010. In April 2013 it displayed 2 white dots which by May 2013 had increased into about 100 white & 200 black dots. I found out that this is an end of life wear out of the DMD chip where the digital micromirrors get stuck. This is a bummer paying $5K for the TV that lasts less than 3 years and finding out that Mitsubishi no longer sells the replacement light engine, nor are their authorized service centers willing to do out of warranty work on the TV set even though I'm willing to pay them to replace the Texas Instrument part number 1910-6143W chip (Mitsubishi part number 276P595010). I was not willing to take Mitsubishi's $1000 buy back offer if I could fix it myself for less than $200.00 using only 4 screw drivers (a Star Head/TORX® T20, a # 2 Philips, a # 1 Philips and a # 2 flat blade).

I found the 52 page L75-A91 ( Version 9.0 dated 11/12/2010 ) service manual online at:

http://www.nodevice.com/manual/l75-a91/get118503.html

It cost me a little over $5 to download as a 17.9Mb Adobe pdf file.

All other Laservue Model service manuals are there too.

I purchased the replacement chip which arrived June 13, 2013. Prices for the chip range from $135 purchased directly from China to $190 from ShopJimmy.com.
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The Service Manual only recommends removing as Field Replaceable Units the (1) Electrical Chassis Assembly, then (2) the Laser Light Source, and finally (3) the Optical Light Engine. The following 3 part numbers are what you'd search for on the internet.

(1) ASSY-CHASSIS 955B394002
(2) ASSY-LIGHT-SOURCE 870B009001
(3) ASSY-ENGINE 870B010001 (This is the assembly where I'll be replacing the defective chip.)

Clean up and remove as much dust as possible before you start the job, pay particular attention to the laser light source heat sink and fan assemblies that will likely have a lot of dust accumulation. Clean up all the dust you can. Wear clean, white cotton gloves and a grounding strap (both available at just about any electronic store) when you do this job. Static discharges that you can't feel can kill or injure sensitive electronic parts so grounding yourself is essential. Use anti static bags to lay the DMD board & chip on when you're working on them. Take care not to touch the micro mirror side of the chip or allow it to touch the table when you remove and reattach its heat sink. Treat exposed optics with care. Use an air brush designed for optical lens cleaning to remove dust. I've found that a brand new unused Swiffer duster wiped gently across the optical surfaces (but not the chip) does a great job while not harming them. I cannot stress enough how important it is to clean all optical surfaces you see. Any dust in the optical path (especially on the DLP chip) will result in gray splochy areas on an otherwise black screen. Rebuilding the Light Engine is best done in a Class 100 clean room or flow bench.

The laser light source in this TV can permanently blind you if you look directly at it or even have reflected laser light enter your eye. I was not worried about the laser though since the laser was not powered during the repair, and I assured I reinstall all protective shields the way they came off.

Because I've never repaired a TV before, it took me 4 hours to get to the defective DLP chip, and 2 hours to reassemble the TV.

My Laservue is back to its beautiful self again. I may buy a spare DLP chip to have on hand because this Laservue failure mode is well worth fixing.

Replacing the zero insertion force chip was easy after I got to the DMD board located on the bottom of the light engine, but to do that I had to:

1. Remove the 13 each Torx screws holding the rear cover on (8 on the back, 1 on the bottom left side, and 4 on the right side in the fan shroud) to remove the rear cover.

2. Remove the 6 each # 2 Philips screws securing the rear cabinet frame assembly (2 at the top, 2 at the bottom, and 2 to the chassis assembly) to remove the frame assembly.


3. I had to remove all of the connectors from the back of the chassis. Reassembly was easy because I labeled them with numbers as I removed them. I also had to remove three cables leading to the Laser Light assembly. Remove the cables by compressing the cable lock prior to pulling each connector out. Remove the 1 each Philips screw securing the electrical chassis assembly (it is located on the left side on the bottom of the electrical chassis) to remove the chassis. Slide the chassis up and out of the cabinet.
4. Remove the 8 each Philips screws securing the laser light source assembly. I only had to remove 3 cables from the Laser Light Source that ran between the Laser Light Source and the Chassis. You might do it differently. You can get 'stick-on numbers' to identify the cable and the adjoining plugs from Frys to help reassembly.

5. Remove the 3 each # 2 Philips screws securing the black plastic Service Cover to the top of the light engine assembly to remove the Service Cover.

6 Remove the 4 each # 2 Philips screws securing the light engine to the TV case. You'll have to remove all the wire and cables from this assembly. Mitsubishi doesn't recommend disassembling this assembly any further than to replace the DMD fan. But this is the assembly possessing the defective chip that is replaced in steps 7, 8 and 9.

7. Remove the 5 each # 1 Philips screws securing the ventilated cover with the DMD fan. Also remove the connector (blue arrow).

8. Before removing the DMD board from the bottom of the Light Engine you'll have to remove the 2 ribbon cables. The way you remove these cables is by unlocking them from the connector. Gently compress the black ears located to the sides of the ribbon cable and simultaneously applying extraction pressure to the ears (NOT the ribbon). When you feel the black ears rise, you're done. The ribbon cables are now unlocked and can be extracted. Do not touch the exposed ribbon cable conductors as your finger oils will cause a corrosion resulting in failure.

Remove the DMD board from the bottom of the Light Engine by first removing the 2 each Heat Sink screws securing the heat sink, and removing the 5 each # 1 Philips screws.

9. Rotate in a counterclockwise direction the flat blade black screw located to the side of the chip to unlock and remove the defective chip.

Reassembly.

10. Insert the new chip and rotate the screw located to the side of the chip to lock and secure the chip by rotating the locking screw in a clockwise direction.

11. After cleaning off the old grey heat sink tape that Mitsubishi installed, apply a thin coating of thermal compound to the heat sink contact area and reattach it.

I used some "Antec® Formula 7 Nano Diamond Thermal Compound" because it had the highest conductivity of 8.3W/mK. It cost about $15 at Fry's Electronics® but I'd estimate it is 2 to 3 times better at heat conduction than what the manufacturer used. I was taught in my Chemistry classes that every 10 degrees roughly doubles the rate of reaction. Since heat speeds the chip aging process, I figured using the best thermal compound would extend the chip's life.


12. Reinstall the DMD board with the 5 each # 1 Philips screws.

13. Reinstall the DMD boards ventilated cover with 5 each # 1 Philips screws; and reinstall the fan connector.

14. Reinstall the Light Engine with the 4 each # 2 Philips screws.

15. Reinstall the 3 each # 2 Philip screws securing the black plastic Service Cover to the top of the light engine assembly.

16. Reinstall the 8 each # 2 Philips screws securing the laser light source assembly.

17. Reinstall the 1 each # 2 Philips screw securing the electrical chassis assembly (it is located on the left side on the bottom of the electrical chassis).

18. Reinstall the 6 each # 2 Philips screws securing the rear cabinet frame assembly (2 at the top, 2 at the bottom, and 2 to the chassis assembly).

19. Reinstall all electrical connectors. Verify each is firmly seated again. Again, check to make sure all electrical connectors are reinstalled.

20. Reinstall the 13 Torx screws holding the rear cover on (8 on the back, 1 on the bottom left side, and 4 on the right side in the fan shroud).

21. Connect HDMI inputs back in, plug the TV back in to AC power and start it up.

Calibrate if necessary.

Edited by Antiepa - 6/22/13 at 12:38pm
post #2 of 24
Thread Starter 
No calibration was required. The set powered up perfectly without any dots.


Edited by Antiepa - 6/22/13 at 12:46pm
post #3 of 24
Wow, great job documenting that procedure. Good to see that the DMD is indeed replaceable in these high dollar sets. Just wondering why Mits seems to be turning their back supporting their last, best DLP based TV. I hope others having the DMD problem find this thread.
post #4 of 24
I purchased my Laservue L75-A91 in February 2011. The picture started fading in and out for a couple of months and finally the tv just shut down. Mitsubishi states the light source assembly needs to be replaced. Since this part is no longer available, will replacing the chip 1910-6143 fix my problem?
post #5 of 24
Thread Starter 
Probably not. Replacing the 1910-6143W chip will only fix the White/Black dot problem. Your problem may be caused either by the Power Supply Chassis, or the Laser Light Source.

Have you tried the following reset procedures?

1. System Reset, Press the side panel "POWER" button and hold it for 8 seconds.

2. Audio/Video Reset, Press the side panel "ACTIVITY" + "VOL left" buttons simultaneously holding them for 10 seconds.

3. User Level Initialization, Using the remote, press the "MENU" button followed by 1, 2, 3 number keys, and then the ENTER key.

When I first opened up my set, the Laser Light Source heat sink was caked with dust. I was surprised that it wasn't overheating and shutting down. If it had shut down due to overheat, the shop manual says that the Power LED indicator on the bottom right of the screen (which is normally green) would be a constant yellow. A blinking red Power LED indicates a circuit failure where the Self Diagnostic Test should be performed. A blinking yellow Power LED indicates that you have a problem with the "Cabinet panel or assembly problem" which too requires you to perform the Self Diagnostic Test. A defective Laser Light Source is indicated by the Power LED on the bottom right of the screen emitting a constant red color.

Self Diagnostics are activated by pressing the side panel "ACTIVITY" + "CH down" buttons at the same time and holding them for 5 seconds.

You read the 2 digit error code by counting the number of flashes emitted by the Power LED in 2 separate groups separated by a pause between groups of about 1/2 second. For example, if the error code is 12, the LED will flash one time, pause, and then flash 2 times. The error code is repeated 5 times.

The shop manual lists symptoms for the following error codes: 12, 13, 15, 17, 18, 23, 25, 26, 29, 33, 37, 39, 45, 46, 48, 56, 57, 67 & 68.
Edited by Antiepa - 6/20/13 at 6:15pm
post #6 of 24
Honestly you "are the man" for taking the time to do this. Will be taking this project on soon.
post #7 of 24
Great post! ( I hope I don't need to use the post smile.gif !) I was fortunate enough to be under warranty when my dots began on the A91. Don't feel bad about how long it took for you to do it. Two authorized service people took over two hours in my home to replace the chip...which turned out to be defective with a yellow discoloration. They came back and hauled the set to their shop and replaced the new dlp chip. Returned the set in perfect condition. I do love the picture!
post #8 of 24
Antiepa,

How many hours were on this set before the DMD failed?
post #9 of 24
Thread Starter 
I bought my Laservue L75-A91 on May 31, 2010. It started having problem pixel white/black dots in April 2013. By mid June 2013 it had hundreds of black & white dots after a total of 9896 hours of run time. That is 10 times less than what the DMD manufacturer's Reliability Growth predictions indicated back in 1997.

I read a paper on the DMD failures. It said that the primary failure mode is hinge fatigue and particulate contamination. The remaining three contributors to nonfunctional mirrors were capillary condensation, CMOS defects, and van der Waals forces.


Edited by Antiepa - 7/1/13 at 3:31pm
post #10 of 24
So roughly 10k hours and 24 months... That is high usage I am at 5k hours on a 19 month old 92840... I have owned several DLPs over the years and none exhibited this issue. The non-laser sets were easier and much less expensive to find extended warranties. for I bought 4 extra years via a Costco Square Trade Warranty for a little over a hundred bucks.. for just such a case. The problem with the lasers is the lack of light engines and used spare parts in general will likely be wickedly hard to find, based on the low production numbers. One could likely find used working sets to scavenge light engines from as the light engines are pretty much same for each specific model year, so a 73" should work in a 92". Mits should be horsewhipped for not having spare light engines on such expensive sets.
post #11 of 24
Thread Starter 
Actually roughly 10k hours in 36 months which at 19 months is 5279 hours.

My usage rate is almost the same as yours.

Your TI 1910-6143W DMD chip will catch up to my failed chip in about 17 months.

Regards,
post #12 of 24
biggrin.gif Thanks for this writeup! I just successfully replaced the DLP chip in my L65-A90 (65", 1st gen Laservue) successfully and eliminated all of those white dots/dead pixels... same part number as the L75-A91. In the L65-A90, pulling the optical engine out and taking care of the optical cables had me very nervous, I've never had the TV apart this far.
post #13 of 24
Thread Starter 
Congratulations!

Considering all the photographs in my post, how similar did you find the L65-A90 to the L75-A91?

What did you have to do different?
post #14 of 24
Quote:
Originally Posted by Antiepa View Post

Congratulations!

Considering all the photographs in my post, how similar did you find the L65-A90 to the L75-A91?

What did you have to do different?

The L65-A90's internal layout is quite a bit different than the L75-A91, and based on your pictures, I would say the L65-A90's internals are more delicate, primarily because the laser assembly/light source is not directly connected to the optical engine. Instead there is a three foot bundle of fiber optic cables that connect it to the optical engine, and even though this cable is wrapped in a metal flexible shroud, it is part of the optical assembly and cannot be disconnected.

The service manual does a decent job of describing disassembly - take the back upper panel off, disconnect all of the cables to the power supply/TV motherboard unit and remove it. Once that has been removed, I removed the screws holding the laser assembly and carefully slide it away from the back of the TV and connect the brackets to allow it to hang from the back of the TV. This exposes the four fiber optic cables that connect to the laser modules (yes, four.. I thought there was only RGB so four surprised me) and this is where I got frustrated with the service manual because it misleads you to believe you shouldn't loosen or tighten the 8mm nuts that hold the cables on. So, trying to honor the warning in the service manual, I tried every other possible way to disconnect the optical cable only to do exactly what they were warning me not to do - disconnect the optical cable tip from the fitting! Seeing a 2 inch section of raw fiber optic cable scared me and I thought for sure I had ruined the cable.

Once the fiber optic cable bundle has been disconnected from the light source, it is just a matter of removing the lower back panel, unscrewing the optical engine and sliding the whole assembly out, exposing the lens, mirror, and a "V" shaped mirror that can be adjusted for physical geometry alignment. From there, I believe there are three or four screws that hold the DLP module in place and it follows your pictures almost exactly from that point.. the biggest problem being that you're having to be careful of the three foot fiber optic cable attached to the DLP module the entire time.

After replacing the chip and following your advice to scrape away the thermal tape and replace it with thermal transfer grease, I began reassembly and managed to carefully work the "damaged" fiber optic cable tip back onto the cable, said a short prayer before hitting the power button and was very happy to find that everything worked and the dead pixels were gone.

Unfortunately, I'll need to pull apart the unit again and use camera lens cleaner on the mirrors as I picked up a little bit of dust which does affect the picture slightly with small areas of the screen showing a slight reduction in luminance when viewing the 50% gray test pattern. The mirrors on this unit are "wide open" once the back panel is off and just handling the assembly made me very nervous.

So far the unit is back to "good as new" condition! Considering that my L65-A90 was a display at Fry's Electronics (and was heavily discounted), I'm not surprised that the DLP chip began to wear out - it had over 7,000 hours according to the internal diagnostics page when I bought the unit, and I'm still very happy with this TV.. in my opinion, it still holds its own compared to even the newest sets available, and the 24fps native playback feature is just now starting to show up in newer TVs. I'm debating whether it makes sense to purchase a second DLP chip and keep it sealed since I don't know how much longer they'll be making these, and $200 to restore the set to new condition was totally worth it.

For anyone considering this, I spent about 9 hours total between disassembly, cleaning (vacuuming) dust out of the set, and reassembly but I'm very slow and picky, so it may not take you nearly as long as it took me.
post #15 of 24
I currently have a L75-A91 and I have noticed the picture seems like it is dimming for a brief second and then going back to normal.. its hardly noticeable until your looking for it... Its kind of hard to describe what its doing. You know how when you change the color temp on the TV it changes the brightness/color of the tv? that seems like what it is doing on its own for a brief second every few minutes.

what could be causing that, and what part would I need to correct it?

thanks
post #16 of 24
Mitsubishi LaserVue L65A90 was purchased in 2009 $6000 and just got my first white spot . I ran this tv all day long hours and hours .I just left it on
most of the time except sleep time . Hoping Mitsubishi will at least send me the chip part . Someone should make a youtube video . You mention camera lens cleaner on the mirrors ???? How was this done exactly ? and scrape away the thermal tape and replace it with thermal transfer grease ???
post #17 of 24
Mitsubishi has screwed me over .... NM
Edited by brownhatter - 1/21/14 at 5:03pm
post #18 of 24
HEY I got my money from Mitsubishi cool thing they did not take the tv so $2100 is mine and tv mine .So ready to replace part . Is there a youtube video on how to repair ? And where do I buy exact right part ....cool.gif
Edited by brownhatter - 1/22/14 at 12:23pm
post #19 of 24
That looks nothing like my Laservue L65-A90 after I opened it up .Wow now what do I do ?eek.gif Called service in my area no one worked on these .
Edited by brownhatter - 1/24/14 at 11:13am
post #20 of 24
Backside of L65-A90



Service manual I found at https://www.completeservicemanuals.com/index.php?_a=product&product_id=1430 but does not show how to remove dlp chip mad.gif
Edited by brownhatter - 1/26/14 at 7:26pm
post #21 of 24
ok I in the middle of changing my L65-A90 dlp chip wow so much easier then the L75-A91 .The board sits right off the back .Just waiting for the Antec® Formula 6 Nano Diamond Thermal Compound.
I did not get the formula 7 store only had number 6 ... hope this works back to work
post #22 of 24
Well it was as easy as changing a computer processor on my tv .But not working after completion . Nothing won't even turn on .
Maybe I got a back chip ?
post #23 of 24
Solution one screw on back was not on tight ... blinking code I could not read because I am color blind . Working great !
post #24 of 24
Did you ever work on your L65 - A90 ? Way different .Chip was easy to change now I got dirt on the picture not sure what the problem ?
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