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.