Why is there no power to my Samsung TV

Question

Samsung UN43NU6900FXZA Television

43 Inch 4k Samsung Flat Screen LED TV.

crwdns2934591:04crwdne2934591:0 crwdns2934593:0crwdne2934593:0

Sam Madland @sammadland

crwdns2934065:0crwdne2934065:0: 25

1

crwdns2931729:0crwdne2931729:0: Sun 17, 2021

crwdns2933897:0crwdne2933897:0

Why is there no power to my Samsung TV

I have a second hand Samsung TV model no:UN43NU6950FXZA that may have experienced a power surge with it's previous owner. It had no standby power light(the red LED) and naturally would not turn on when the power button was pressed, nor by remote control. I have tried plugging it into different outlets and surge protectors(all working) as well as holding the power for 30 seconds while plugged in/unplugged to reset it. Still wouldn't turn on.

Since none of those worked I took off the back panel and found a replacement main board(same board version:BZ01). I replaced it with the new one, all cables plugged in the same way and closed up the case. When I plugged it back into my working surge protector outlet it still has no red standby light and will not turn on

So I'm wondering if there's anything I've overlooked or if it's something to do with the backlight LED array being fried and needing to replace that too.

crwdns2934081:0crwdne2934081:0 crwdns2934083:0crwdne2934083:0 crwdns2934093:0crwdne2934093:0

crwdns2934109:0crwdne2934109:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0

crwdns2889612:0crwdne2889612:0 2

crwdns2934285:0crwdne2934285:0

crwdns2933313:01crwdne2933313:0

crwdns2934051:0crwdne2934051:0

jayeff @jayeff

crwdns2934065:0crwdne2934065:0: 449,1crwdns2936485:0crwdne2936485:0

11

366

1,4crwdns2936485:0crwdne2936485:0

crwdns2931729:0crwdne2931729:0: Sun 17, 2021

crwdns2933897:0crwdne2933897:0

Hi,

Have you checked that the fuse on the board is still OK and not that it blew when you connected it all up and applied power to the TV, you didn’t say?

Disconnect the power from the TV and use an Ohmmeter to check the fuse.

If you still have the old mainboard/power board check its fuse also to see whether it is OK or not.

If it is blown then the reason for that will have to be found. You could try replacing the fuse and then disconnecting the LED backlights and then connecting the power to the TV and check if the red standby light comes on.

If not check the fuse again and if it is OK then check if the IR board is OK. If the power button is on the same board it may be causing the problem. This is only conjecture but you have to start eliminating things in order to find out what’s wrong.

It would be a lot easier with the schematic or a service manual but I can’t find either. You may have better luck

Be safety aware when working in the back of the TV as there is exposed lethal AC power on the board when the power is connected to the TV. Stay focused on what you are doing.

Note:

The fuse is designated as 250V T3.15 AL so make sure that the fuse is a 250V 3.15 ''slow blow'' axial fuse as a standard (aka fast acting) 250V 3.15 fuse would blow immediately when the power was connected due to the high inrush current when the power is first connected. T= Timed (aka slow blow)

A slow blow fuse is designed to hold for the 10-12 mS before this current subsides. Getting 10 fuses may also help if you need to replace it a few times during the course of testing where the problem is.

I mentioned that it is an axial type that you have to search for or get as that signifies that the type of fuse has wire pigtails so that it can be soldered to the board and that it is not one that just plugs into a fuse holder

(click on image to enlarge for better viewing)

crwdns2934105:0crwdne2934105:0

crwdns2853045:0crwdne2853045:0 crwdns2853046:0crwdne2853046:0

crwdns2889612:0crwdne2889612:0 2

crwdns2944067:02crwdne2944067:0:

Sorry for the late reply, finally got around to opening things back up and tested the continuity on the fuse for both old and new mainboards. Both give a tone and appear to be fine so that doesn't seem to be the problem. I also took a look at the IR/power button and it doesn't look damaged although I may see about finding a replacement for it just in case I'm missing something

crwdns2934271:0Yan 1, 2021crwdnd2934271:0 Sam Madland crwdne2934271:0

@Sam Madland

If the fuse is OK you need to check that the standby voltage being supplied by the power board to the mainboard.

It is the mainboard that turns on the red standby LED indicating that power is connected.

There should be some mention of a STBY test point somewhere on the board

crwdns2934271:0Yan 1, 2021crwdnd2934271:0 jayeff crwdne2934271:0

crwdns2934285:0crwdne2934285:0

Sorry for the late reply, finally got around to opening things back up and tested the continuity on the fuse for both old and new mainboards. Both give a tone and appear to be fine so that doesn't seem to be the problem. I also took a look at the IR/power button and it doesn't look damaged although I may see about finding a replacement for it just in case I'm missing something — Sam Madland
@Sam Madland

If the fuse is OK you need to check that the standby voltage being supplied by the power board to the mainboard.

It is the mainboard that turns on the red standby LED indicating that power is connected.

There should be some mention of a STBY test point somewhere on the board — jayeff

Samsung UN43NU6900FXZA Television

Why is there no power to my Samsung TV

crwdns2933313:01crwdne2933313:0

crwdns2934229:0crwdne2934229:0