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Sanyo DP40142 LED/LCD TV Repair

By on October 8, 2018
oscilloscope kitset











I was watching my Sanyo DP40142 LED/LCD 40” TV the other day, and the screen just went black! I got my flashlight and checked the screen to see if the panel also went out, but it was still working, praise The Lord! So I knew that the problem was just affecting the backlight.

I went to turn on my vacuum cleaner to vacuum the dust off of the TV and my vacuum cleaner quit and tripped the breaker, as I mentioned in the previous article on my Hakko FX-888D soldering iron repair.

sanyo led tv repair

sanyo led tv fix

sanyo led tv fix and repair

sanyo dp40142 led tv fix and repair

So the first thing I did after checking the screen and taking the back off of the TV was to look the boards over good, and start checking voltages.

The voltages checked fine. The TV is not shutting down so I would imagine that there are no short circuits.

sanyo dp40142 led tv fix

sanyo dp40142 led tv repair

Here are some photos showing the IR board and Mainboard. The T-Con is integrated into the Zoran ZR748 SupraHD SoC, on the mainboard. The LED driver board must be inside the LCD module. I’m not sure why Sanyo calls it a LCD module. I would call it the LCD case.


Above are the Schottky Barrier Diodes and N-Channel Enhancement-Mode QFET/MOSFET’s. I removed them to put some fresh thermal compound on them. I also did the same with the Bridge Rectifier, which you can see in the next photo. The TV is six years old, so it’s a good idea to freshen up the thermal compound.

bridge rectifier led tv

sanyo led tv mainboard

brymen tbm869

In the photo above I am checking the voltage on the backlight DIM line with my amazing Brymen BM869s DMM and noticed that there is a 1.580V AC signal on it. I checked the connector on the mainboard to verify that the signal was coming from the mainboard and not the IR board, and it was.

I checked the AC signal with my Tek 2465A-DV oscilloscope. You can see in the next photo that the signal is a nice PWM square wave running at 119.9989Hz.

tektronix 2465a

JYE Tech DSO Shell Digital kit oscilloscope

In the photo above, I am checking the square wave signal with my small inexpensive JYE Tech DSO Shell Digital kit oscilloscope that I bought awhile back. It is reading the signal at 120.064Hz with a Duty Cycle of 62.4%. That is only 0.0651Hz off from my Tek scope. Not too shabby for an inexpensive little digital kit scope! I didn’t check the duty cycle with my Tek scope, but that looks about right judging from the graticules.

You will notice a vertical white line on the little DSO Shell scope display screen. If the seller had googled my name, they would have seen that I write electronics repair articles and that the scope could appear in one of my articles. They would have made sure that the screen they sent to me was perfect.

Or, maybe they sent it on purpose, hoping that I would repair it and write an article about it. Who knows?

After I get my oscilloscope taken care of, and build some test equipment that I need to build, I might look into repairing it. It does kind of get on my nerves.

bad capacitor in sanyo led tv

I decided to upgrade the primary filter cap with a low ESR Nichicon 105⁰C E-Cap. The new E-cap is quite a bit larger than the original and is rated 30 volts higher. It hangs off of the IR board a little bit, but that is no problem. There is plenty of room.

I put some clear indoor adhesive onto the E-cap to help hold it in place and give the leads some strain relief. The other e-caps look good.


In the photo above, I am testing the LED backlight with my TKDMR Model #TD3H backlight/component tester. There is no light emanating through the back of the LCD module.

lcd panel sanyo

I have the LCD screen and diffusers removed from the case and stacked onto a table. I taped the LCD panel board carefully onto the LCD screen with masking tape to keep from damaging the TFT’s. Masking tape is pretty easy to remove and doesn’t leave a bunch of adhesive on things.

I don’t trust suction cups much, so I used a piece of ply board with a thick towel over it to slide the LCD screen onto so I could remove it from the LCD module and carry it to the table safely. It worked out great.

sanyo led tv backlight

Everything is removed and you can see the LED driver board inside the LCD module. I’m ready to remove it from the module and start checking the LED strips.

sanyo led tv backlight strips

sanyo led tv backlight tester

With my backlight tester hooked up to light all of the LED strips, they did not light. After removing the first strips, (A) and (C) [that were hooked end to end with a small coupler], the rest of the strips lit up just fine. So I know that the problem is somewhere in one or both of the (A) or (C) strips, and that the LED driver board is probably ok.

The very first LED on the (A) strip would not light, and the third and fourth LED’s would light up weak and sporadically because of cold solder joints. I went ahead and fluxed/re-soldered all of the LED’s on the (A) strip with my soldering iron.

The LED’s lit up great on the (C) strip, but one connector pad that couples into the (A) strip through the coupler, had a little burn mark on it.  The spring-pin for that pad inside of its coupler wasn’t sprung down well enough to make good contact with the contact pad either. I forgot to take a photo of it.

So I cleaned up the pad with emery cloth and alcohol and reached inside the coupler with a needle and bent the little spring-pin down some so it will make better contact with the connector pad.

led tv strips

In the photo above I am letting the adhesive set up on the LED light refractors for several hours. I forgot to get some Super Glue gel the last time I was at the store, so I used some small dots of E6000 adhesive to hold them down. I’ll go ahead and re-solder the LED’s on all of the strips if I have problems with the LED strips again.

led tv strips sanyo

Success!! The LED’s are working great! I repaired my TV and it didn’t cost me an arm and a leg! With the LED backlight tester outputting 122V at 59mA, the softly lit LED’s make a beautiful picture! Mr. Yong may choose to use this photo for the articles thumbnail!

led tv module sanyo

Now my Sanyo 40” LED/LCD TV is back together and lighting the LED’s very well. We can see some light emanating from the LCD module.

lcd tv panel holder

Looking from the back of my adjustable-top TV repair table, we can see the TV showing the Star Trek movie through the tempered glass. It looks like another successful repair is in the books. Now it is time for me to rebuild the fan motor and upgrade my Tektronics 2465A DV oscilloscope, and then start building some nice electronics test equipment. Till next time – take care, guys!

Please leave any comments or suggestions that you may have below. Thanks!

robert calk junior

Robert Calk Jr., is a Hobbyist from the U.S.A. that loves Electronics Device Repair.


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Please check out his previous repair article below:





  1. Mark

    October 8, 2018 at 7:25 pm

    Hey Robert,
    Good article and congrats on the repair.
    I have a JYE Tech DSO138 DIY Digital Oscilloscope that I put together that works really well. Did you assemble a kit or buy it complete? It might just have a bad connection on the screen.
    Nice job sorting out the LEDs.

    • Robert Calk Jr.

      October 8, 2018 at 9:17 pm

      Hi Mark,

      Thanks! It was a partially assembled kit. But it was fun - I enjoy putting kits together. And it is a pretty good scope. I was also thinking a bad connection on the screen. I will check it out one of these days. It doesn't affect the operation of the scope so I didn't worry about it. It is a nuisance though.

  2. Claude

    October 8, 2018 at 7:34 pm

    Very interesting how you detected the problem step by step. Trying hard to learn how to detect electronic issues.

    Your articles are great.

  3. Humphrey Mndaka

    October 8, 2018 at 8:15 pm

    Hi Robert Calk Jr, Amen the machine finally worked. My afternoon made..Thanks.

    Regards Humphrey

    • Robert Calk Jr.

      October 8, 2018 at 11:04 pm

      Thanks Humphrey. I'm glad that you enjoyed the article. I wonder how many people just replace LED's when the problem was just bad solder joints?

  4. Albert van Bemmelen

    October 8, 2018 at 8:17 pm

    Another great article with clear sharp photos and text balloons Robert! I recently bought that same Led tester after you recommended it, and sold my previous tester for less to my shopowner friend. I wonder how you did know that the T-Con board was integrated into the Zoran ZR748 SupraHD SoC? Were you able to get or buy a service manual for your about 6 year old 40 inch Sanyo? Because these aspects are not exactly general knowledge.

    • Robert Calk Jr.

      October 8, 2018 at 11:16 pm

      Thanks Albert. I am glad you enjoyed it. It is the first time that I have used one of the backlight testers. Just because I talk about something doesn't mean that I recommend it. I just liked the 1mA switch and the Pot's for adjusting the voltage and current. I don't like devices that doesn't allow us any control.

      It is mentioned in the service manual that the T-Con is integrated into the Zoran SoC. But I figured that it was because I couldn't find a T-Con board anywhere. I downloaded the service manual 4 years ago to make sure that I would have it when I needed it.

      • Albert van Bemmelen

        October 9, 2018 at 2:09 pm

        You were smart buying that service manual for your 40 inch Sanyo tv too in case you would need it Robert! The photo of the 122V at 59 mA working backlight leds with not all refractors glued on yet is a perfect demonstration why the TKDMR Model #TD3H backlight/component tester is an improvement over the standard testers without those extra pots. And using the small dots of E6000 adhesive glue was something worth knowing too! Using normal superglue can negatively effect the transparancy of the refractors because of the cyanide fumes coming from the glue. But knowing there are so many types of glue like E7000, E8000, T6000, T9000 or B6000 I am unaware of their specific application.

        • Robert Calk Jr.

          October 10, 2018 at 2:13 pm

          Thanks Albert. I'm pretty sure that I had to pay for the service manual, but I don't remember for sure. I figured that someday I would need it. I'm not sure how much fumes would come from a few small dabs of superglue. The E6000 is a high-strength adhesive. I am hoping that it can handle the heat of the LED's. We will find out.

  5. Robert Calk Jr.

    October 8, 2018 at 9:31 pm

    Thanks Claude! I am glad that you enjoyed the article. I started by getting books and learning the basics. Then I bought Mr. Yong's e-books, and many of the e-books listed on this website. That's the best way to learn; get the books, tools, and practice!

    But be careful and take your time - one mistake in electronics could be your last. And you must use an Isolation Transformer even if you have to build one yourself! And if you get tired and sleepy, stop and get some rest before you apply power to any device!

  6. Parasuraman S

    October 8, 2018 at 9:51 pm

    Very thorough, detailed article with running commentary! Superb work, indeed! Achieved what you wanted to inspite of all hurdles! Great! Very positive and hilarious way of looking at the supply of DSO!

    • Robert Calk Jr.

      October 8, 2018 at 11:26 pm

      Thanks Parasuraman. I am glad that you enjoyed the article. That means a lot to me coming from you guys that are a lot more experienced and knowledgeable than I am! But I'm learning and having a lot of fun doing it!

  7. Yogesh Panchal

    October 9, 2018 at 12:16 am

    lots of effort and detective work!
    Good Job Sir.

    • Robert Calk Jr.

      October 9, 2018 at 11:05 am

      Thanks Yogesh. I am glad that you enjoyed the article.

  8. Dave Smith

    October 9, 2018 at 4:37 am

    Very impressive Robert:) My company, Canada Training Group, teaches deductive reasoning to industrial troubleshooters throughout North America. Would you be interested in doing some part time instruction?

    Dave Smith
    Canada Training Group

    • Robert Calk Jr.

      October 9, 2018 at 11:14 am

      Thanks Dave. I am glad you liked the article. I don't think that I would be qualified for that. Besides that I am disabled with a bad back and neck that prevents me from standing or moving around much. I appreciate the offer though. Thanks.

  9. beh

    October 9, 2018 at 11:47 am

    Hi Robert
    Great repair, well done .

    • Robert Calk Jr.

      October 9, 2018 at 1:30 pm

      Hi Beh,

      Thanks Beh. I am glad that you enjoyed the article. I almost had a Samsung 65" or so to repair, but it has a clearly busted screen where something hit it.

  10. Andre Gopee

    October 9, 2018 at 11:06 pm

    Nice Jon Robert, Nice to know that the TV was working and just the back lights failed. I have to buy one of those LED testers, its a nice tool to have. Thanks for sharing.

    • Robert Calk Jr.

      October 10, 2018 at 2:20 pm

      Thanks Andre. Yes but the LED's were good, just cold solder joints. The LED tester seems to do a good job. I haven't had time to test it on components yet.

  11. Eric Leung

    October 10, 2018 at 10:48 am

    Great article! I have repaired several LED tv failed in Led strips. Unfortunately, I also broken some panels during removal operation. Can yu show me your method to remove the panel? highly appreciated. Thanks

    • Robert Calk Jr.

      October 10, 2018 at 2:28 pm

      Thanks Eric. I am glad that you enjoyed the article. I explained it to you in the comments on Albert's TV repair article. I basically just use a piece of plyboard covered by a thick towel in one hand while lifting the panel up with a suction cup a little bit. Then I just slide the panel onto the covered plyboard and set the whole thing down on a table.


    October 10, 2018 at 2:07 pm

    Thanks I am glad that to receive this article. I received many from Mr. Yong's I want to get his books, but we are in africa , in Sudan & we have no way to buy outside our country

    • Robert Calk Jr.

      October 10, 2018 at 8:51 pm

      Thanks Mubaruk. I am glad that you enjoyed the article. I am sure that if you email Mr. Yong yall can find a way for you to get his e-books. Take care.

  13. Humberto

    October 12, 2018 at 12:01 am

    Wow! Robert, congratulations. You have done a real repair step by step, taking into account a great patience. By the way, you own good tools.

  14. Robert Calk Jr.

    October 12, 2018 at 8:40 am

    Thanks Humberto. They are pretty good tools for what I can afford. People that have more money have much better tools than I do.


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