Samsung LE40A859S1M - Panel defect - gate driver shorted - funny experiments with flashlight shooting at chips

This is not a success story, for a change. I bought the TV from eBay for 11€. The images of the seller were not inviting and that's why only one other bidder (obviously the seller's friend) had joined.

I learned something about image patterns, which appear when the gate and source driver chips fail on a panel.

Those were the pictures from ebay:

I did not see any horizontal lines, which are reliable indicators of panel faults, so I joined the auction. The blotchy, uneven image I had seen before with TCONs, which lost power.

This TV was the first LCD with fans. Not a bad idea at all, but boy, where they in a miserable condition!

Power supply fan:

TCON fan:

Clogged intake in back cover:

The device cleaned up. Oh my, the wiring!

I fired up the machine and there they were, the horizontal lines. Uh oh. Lines like this are 100% panel problems:

The inner, regular noise was probably the TCON's fault:

Image ghosting:

Weird red clouds in the upper right area:

Some other weirdo color smears:

I cleaned the LVDS connectors with the paper trick that norcal715 showed in one of his YouTube videos. There was quite some dirt on them. Unfortunately, this wasn't the problem.

I found a bad capacitor on the TCON, which buffered the 12V supply, but it had no influence. The image was the same with the cap missing or replaced.

Ok. This TV was very likely beyond repair, so I took the opportunity to explore. I always wanted to dismantle a panel.

Front bezel and frame removed. I wanted to get access to the gate and source drivers, which are integrated in the flat connectors attached to the panel screen:

Connector close-up:

I pressed and bent each of the connectors and none of them reacted. So, the connector bonding was not the problem.

Aha. Some dead pixels in irregular shape right in the area of the first gate drivers!

Could the panel have produced an internal short and that damaged the gate drivers and probably the TCON, too?

Suddenly, the image disappeared and looked like this:

I noticed that the top gate drivers (on the left and right side) got very hot. This panel was dead.

Then, something interesting happened. Just when I shot a photo of the driver with the flashlight activated, the image came back! This driver was light-sensitive and obviously not in order.

That called for experimentation! I picked up my big flash light and fired directly at the chip:

With each shot, the line pattern changed. Also, mechanical pressure on the chip had some effect.
I tried the same with a source driver. Brrrzzzzzzt! The flash killed it :-) Those chips are light-sensitive and too much photon energy causes havoc on them.

I think this incident also roasted something in the TCON, because I never got back the old image I had from the start. It became even more noisy.

A fried source driver:

Now I know the visual symptoms of a failed source driver. The white bar came from the fried chip. Its neighbor didn't look very healthy, either.

The image wasn't stable. It wouldn't take long and the white-out with the horizontal lines came back.

I removed the upper left driver chip and voila: image appeared. To my surprise the area of the missing driver (top left) wasn't looking so bad at all. Strangely, the lower parts looked worse this time.

I cut off the upper right gate driver and bam! Image completely gone:

How these panels work is still a mystery to me. The theoretical explanation I found on the net never included how the source and gate driver chips are organized. The source drivers are easier to understand because they seem to be independent from each other. The gate drivers however are interconnected and the failure of one can influence the others.

I need to study LCD panel internals more.

Samsung LE55B679 - not turning on - power up cycling

Repairing a 55 inch TV is a little daunting. There is no way to handle such a monster with only two hands. The LCD types are not that terribly heavy compared to a plasma, but the sheer size of it makes any maneuver difficult.

However, the opportunity was too inviting and I pulled a Samsung LE55B679T2SXZG from eBay for 165€. The seller said, it won't turn on and the stand by LED would blink constantly. He came home from a holiday trip and the TV would not start anymore. He said it worked perfectly before. That sounded like some power spike had hit the tuner or the mains.

Or finally a case of dead capacitors for me, for which Samsung TVs are famous for?

This thing is BIG:

I switched it on and it was as the seller said. The TV endlessly cycled its power-up sequence. The backlight won't turn on.

Ok, back cover removed. Wires falling off due to failing tapes. The usual.

Already re-dressed wiring. Lonely boards in the vastness of space:

A visual inspection did not reveal any bloated capacitors on the power board. I took my ESR meter and measured all of them. They were all in perfect condition, except for one 50V 47µ, which measured worse compared to an identical one on the board. I replaced it just to be safe. As expected that did not fix anything. I also checked the voltages on the power board and they were all ok with no suspicious noise. The power-ok line coming from the main board went low in regular intervals, which made the TV reboot.

Aha, so the mainboard did some funny things. I unplugged the mainboard connector. The power board then produced all voltages it has. The backlight turned on and it looked even and clean. Good, so the inverters were ok and no lamps shot.

Hang on, the power board had an interesting design date! April 2015? What the heck! (Update: or maybe it was 15th of April 2009?)

So, somebody already took a chance to fix this TV! That properly explained the perfect condition of the caps and why there wasn't any dust inside the case. The cheeky seller did omit this little detail. Fair enough, I got a TV with a brand new power board. Thank you, this narrows down the possible defect sources :-) I guess the amounting repair costs went too high and the guy decided to buy a new TV instead.

I poked around on the main board and tested all voltage regulators I could identify. Nothing abnormal there. Then I disconnected the TCON and soldered a wire to its 13V line to test it in isolation with the bench supply. It pulled a constant 0.7A, which is the usual amount. Chances were high that the TCON was not the trouble maker.

There had to be something wrong with the main board. As all voltages were ok and also all the crystals were oscillating happily, I had no means to further diagnose it. Most likely some memory chip is busted or maybe the tuner or some other chip had blown. A replacement was needed.

The main board's number is BN41-02626V. You have to be very careful here when searching for a replacement. There are plenty of identical-looking boards from smaller TVs, whose number may differ in just the last character. There  is an "R" type for  the 32 inch model, for example, and according to www.samsungersatzteile.com the "V" has two successors "M" and "E". Sometimes the difference is obvious: either the SAT tuner and/or the Ethernet socket are missing.

The board number is printed on the sticker on the tuner. Don't just use the "PCB Code" printed on the board as this does not encode the fitted features.

Any football fans in the engineering department?

At samgsunersatzteile they charge a whopping 240€ for a new "M" type. The "V" is not available anymore. No thanks.

I don't know what the differences are between boards for larger and smaller TVs, but I recon it has something to do with the panels and some factory-preset parameters. I wanted to be on the safe side and looked for an exact replacement. None was available from eBay or from my favorite seller flattvparts.co.uk. After a while I found one for 90€ at the Romanian repair shop piese-servicelcd.ro. It looked like a serious dealer to me and so I ordered the board.

That fixed the TV. Nice.


This will most likely be the last Samsung TV for me. Why? Because their so-called service manuals are utter junk. There is nothing in them besides an incomplete bill of materials, some exploded views, and a silly diagnose flow-chart, which gives you nothing and in my case did not even match the device. There are no schematics. The TVs don't self-diagnose and display error codes with the stand-by LED, unlike Panasonic, Sony or Philips.

Toshiba 37RV635D - distorted picture - wrong model ID and panel ID in system configuration - update via USB fails

This was a fun repair and I have learned a lot from it. I picked up a Toshiba 37RV635D from eBay Classifieds for 45€. The owner said that all of a sudden the image got a yellowish tint. The images he provided showed a lot more than that. Weird image noise and color distortion.

So, when I started the TV at home with a program fed into HDMI, I got this:

Wow, this may go as modern art, but it's far from a good image :-)

Something on the main board is going very wrong, I thought. A TCON board cannot produce such images. There were no errors in the scanning. Everything was at its intended place on the screen, but the colors were all wrong and there was noise inside the shapes, especially where white areas were supposed to be.

Zooming into the image; interesting block structures:

The menu at close-up. The entries were still readable, so I was able to at least control the TV.

The image supplied by my Nexus 7 looked nowhere near the original:

Software Update Woes

At a couple of places I read that re-initializing the TV with a software update could sometimes straighten weird image distortions. So, I downloaded the latest firmware and put it on a USB stick, which I formatted with FAT (not FAT32) as required by Toshiba. 

The TV just wouldn't accept the data on the USB stick, even though the media player was able to navigate into it. I browsed through a number of forums and one guy recommended to format the stick with HP USB Disk Storage Format Tool.  I mean, really? Well, I tried that and it worked! No comment...

Alas, the update did not fix it.

Getting On

Even though I immediately suspected the main board, I started my standard routine checks. 

First, the power supply. Nothing caught my eye there and the caps measured all ok. Only top quality caps. Well done, Toshiba:

The 12V line measured a little low (11,7V) and was pretty noisy:

Well, that must have been the noisiest power supply I have seen so far, but it looked ok, nevertheless. All the regulated supplies on the main board were low noise and the voltages made sense.

Just when I looked up (and found) a replacement main board in my preferred sources, I remembered a repair story in Kent Liew's LCD TV Repair Tips 4.0, where he fixed a similar-looking problem by re-configuring a device via the service menu. It wasn't a Toshiba though, but I gave it a shot. The service manual is available from elektrotanya.com.

Among other things, the service manual describes how to configure the main board properly for the given TV type and panel type:

To switch the Toshiba into service mode, you do the following:

• Press and release the mute button on the remote twice
• Press and hold the mute button on the remote
• Press the Menu button on the TV

All that in quick succession. A red S appears at the top right corner. In the left corner, the individual config settings are shown, which can be paged with the Program Up/Down buttons and modified with the Volume +/- buttons on the remote.

The SETID specifies the TV model. It was way off and complete nonsense! I set it to 11hex according to the model table:

Same thing with the panel ID. It was set to 65hex, which belongs to the 32 inch model with a Samsung panel. Mine is a 37inch with an LG panel!

After that, you press the "Info" button on the remote and the "Program Up" on the TV at the same time. The TV reconfigures itself and reboots.

Tadaaaa! The image was back!

Actually, I had to repeat the process because the IDs were wrong again. Not so bad as the first time, just off by 1. Why? I don't know.

How does that finding fit the description I got from the seller? Normally, I would conclude that someone who had no clue what he was doing swapped the main board with a used one from eBay or so, and got stuck. However, the TV looked untouched. Anyway, it was a cheap and quick repair!

About Toshiba Service Mauals

The manual I've downloaded from elektrotanya comes in a strange format. It consists of a large number of HTML files, images, and DWF files. Opening the start HTML page will complain "The ZEUS engine cannot be located". The manuals require the installation of the ZEUS engine, which is also avaliable as a RAR from elektrotanya. This software is very old (2007) and consist of JavaScript files of the most peculiar kind. The installer says that IE6(!) or higher is required. I couldn't get the thing to run on my W7 64Bit machine with chrome. Bummer!

Some HTML pages may work nevertheless. The setup I've described is located in !adj-sm.html, for example.

Now, what are those DWF files? They are Autodesk project files and contain the schematics and board layouts. Nice! You need to download the free reader program Autodesk Design Review.

When you open a file, you will see nothing. It took me a while to grasp the program. First, the WHITE_MASK in the Layers list must be switched off:

After that, you'll see something like this:

The red thingies are layers for each(!) individual component to indicate its location. That is enormously useful with complex boards like the main board:

But I cannot tell the wood from the trees anymore! Well, you need to switch off all the component layers and then you can zoom into the details as much as you like. To locate a component, just switch its layer on.

This is pretty darn good! I spent so much time searching for components in the vector graphics of the Philips manuals.

The layers which reveal the complete drawing are called:

• 0
• BLACK
• GRAY
• HOLE
• MAGENTA

Unfortunately, some of them are right in between the components in the layer list, so it is a little tedious.

Philips 40PFL9715K - 9 blinks TCON board defect - FDS8813NZ MOSFET failure

A friend of mine is a big Philips Ambilight fan and asked for a TV for his parents. I came across this Philips 40PFL9715K in eBay Classifieds and picked it up for 125€. The seller said that the image unpredictably goes black. A quick test at the seller's place did not show the error and the panel looked 100% ok. That's always the first thing I'd like to be sure of when I start a TV project.

I switched it on at home and - nothing but flickering. TV won't start. Weird. It must be a semi-mechanical problem then. The vibrations during transport already had some influence, obviously.

Also, a regular clicking noise was emitted from the TCON. Oh, I hate clicking TCON boards! With mixed feelings, I opened up the machine.

This device is packed! A sattelite receiver, built-in WiFi with one antenna on each side, two woofer speakers and an Ambilight which also illuminates the top of the TV, not just the sides. And, thank you Philips (or Toshiba, for that matter, who produced the panel and the TCON), the TCON is deeply buried under plenty of cables and the holder for the stand. I hate this!

As always, some tapes and cable guides were loose due to dried glue. And some sloppy wiring here and there. Philips is not Panasonic or Sony:

The "eyes" of the so-called woofers reminded me of something...

The first thing I do is to check the power supply voltages. They all measured exactly as it is printed on the board. Except for the 12V line driving the TCON, which is supposed to have 12.5V and only had 11.9V. I found some cheap arse electrolytics:

I removed all the green ones to measure them individually, but none of them had any defect. ESR and capacity were perfect. Anyway, let's use the opportunity and put some quality Nichicon HD in instead. I had to bulge the back cover a little to make room for the big one :-)

The voltage was still at 11.9V, so that was most likely ok and the 12.5V were never there in the first place. A little irritating still. A quick check for supply line noises neither showed anything to get concerned.

I removed the TCON and attached it to my bench power supply to investigate the click noise. This was the biggest TCON board I've seen so far.

It behaved weirdly. Besides the clicking noise, the current consumption flipped between 1.4A and 0.8A. The voltages measured ok, basically, but the one for the big processor wasn't stable and the PWM impulse at the MOSFET gates regularily dropped out for a tiny amount of time.

The processors get really hot and I had to interrupt the diagnose often to let everything cool down. As I mentioned earlier, I suspected a mechanical problem, so I squeezed and twisted the board at various places. Nothing had any effect until I pressed my finger on the FDS8813 MOSFET. The board immediately stabilized. I suspected a wildly chirping DC/DC converter chip first. To find the FET was actually a relief.

A bad solder joint? I reflowed both FETs. The clicking was gone and the jumps in supply current also.

Back in the device, the TCON board behaved well until I plugged in the LVDS cable. Then the clicking started again and the TV standby blinked 9 times, which indicates a non-responsive TCON.

Nevertheless, I was sure that I had found the reason for the defect. Those FETs were not completely dead, but once they got under load, they misbehaved.

I browsed eBay. A refurbished board cost 125€. Outch! But what's this? Someone who had the same problem offered the exact same FETs I had my hands on. Great! And only 10€!

Ordered, soldered in, TCON drew a constant 0.8A, TV worked :-)

Why did the FET(s) die? They run extremely hot. A little heat conducting block connects them to the cover. The two processors steaming along at over 70°C are close by and grill the two FETs. What a cheap and stupid construction, Toshiba! I decided to improve matters and glued a heatsink on top of the FETs. This brought down the temperature there to about 55°C. The horizontal orientation isn't ideal, but I had no choice here because of the flat cables below it.

Also, to improve convection, I drilled holes into the back cover right on top of the heatsink:

I hope my friend's parents will enjoy their TV for a long time.

Can this TV beat a Plasma's image quality? No. Even with its direct LED backlight. Like all of the LCD TVs I have repaired, apart from the Sony, it produces a harsh, a little unnatural image for my taste. I am constantly aware that I look at a TV image. With the Panasonic plasmas, I am able to forget that, immerse into the images and feel like looking into the world (with full HD material at least).

Nevertheless, the Philips gives a very decent performance. The picture is crips, and the sound is voluminous thanks to the extra "woofers". The image tint is too much in the red, which can be adjusted via the individual white balance. The 9er series also has a nice heavy aluminum-style remote with precise buttons, not the cheap wobbly plastic one that the lower series have.

Update

The TV did not last long. My friend had it running for half an hour and then it started rebooting again. Now it doesn't even start at all anymore. Argh! It's going back on the lab table. Let this not be one of the BGA chips, please!

It turned out that the FDS8813 was broken once more. I think I made a mistake during reassembly last time and the transparent plastic piece sneaked between the metal cover and the heat-conducting block for the MOSFET. It is exactly in line and reaches just on top of the chip :-( So, I effectively isolated the chip from its heatsink.

Four evenings intensive testing at over 30° celsius room temperature and it is still running fine. I guess it's fixed for good. :-)

Update 2

The FDS8813 ist the strongest member of the FDS88xx family. It is still resonably cheap and can replace all the other 8880 (the companion FET on this TCON), 8884, 8882 (on some Philips main boards). There is no need to keep the others on stock.