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Thanks for the info. My standby light comes on sometimes. But when it doesn't, my TV doesn't work at all. Would you have any knowledge how this can happen? I have a 75" Model QN75Q7FAMFXZA.
And sorry for the rookie question, which of these is the power board and which is the main board (see picture)?
Thank you.
Here’s a link of pics of my PB.
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Hi @lioneld
If you have a DMM (digital multimeter) when the standby light is not on check if there's 7.5V DC on the STB ref point on the power board.
Here's an image taken from one of the images of the board you just posted showing where it is located.
Measure between the J2 link and an earth point e.g. screwhead of screw holding the board.
If there's no STB voltage or it is the wrong value then the power board is the problem.
If there is then it may be the cable/cable connection (at either end) between the power board and the mainboard or it could be the mainboard.
Be safety aware. Even though you're testing on the cold side of the board there's exposed lethal AC voltage on the hot side of the board. Watch where you place your hands etc
(click on image)
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I was able to test it. It showed 9.94V DC and the stand by light was on.
It's a bit high but maybe still OK. You need to test it when the light is off.
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@lioneld 1 is your main board; 2 is your power board and 3 is your LED driver board. This "standby light comes on sometimes. But when it doesn't, my TV doesn't work at all" is normal behavior. Your standby power is created by the power board and send to the main board. This means that your TV is ready to get turned on etc. The signal for all of that comes from the main board. Essentially, the main board tells the power board which circuits to turn on etc.
If you do not have standby power nothing will work. The first suspect here is the power board. Since this is an intermittent error and only occurs sometimes, check the IC's (chips) on that board. In particular, the ones that are utilizing a heatsink. Check for any damaged looking component and post a close-up picture of your power board so we can assist with that. Just make sure it is a well-focused picture :-)
Just as a sidebar, the large display TV's like yours still have issue with the panel. So right now, we don't rule anything out.
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thank you. I’ll send a high res picture tonight. When the problem started, I would look to see if the red standby light would be on. That’s how we knew we could watch TV that night. It just seems strange how sometimes it’s on and the TV works and other times, it’s off where the doesn’t work at all. I just bought a new TV. But I want to put this one upstairs if I can fix it.
Did you double check that the wall power outlet (or powerstrip?) that the TV is connected to is working OK or is working when the TV doesn't show the Standby power light?
Yes. Both the one connect box and TV are connected to a wall outlet.
@lioneld since this is an intermittent error and if your power LED is on, your power board will/should show the Stby voltage when it is on and no voltage when it is off. This sounds like an issue with a switching IC on your power board. Schematics are not available, so you are going to have to make a tough decision. you could try to continue to narrow this down without schematic or you could try to find a replacement board (even a used one will work at this time) Now use that to determine that this error is the power board and not the panel (Samsung, LG and Philips ae having issues with their large panels shorting out the power supply.
One more thing you want to look at is the backside of the power board. There are a few components as well. Look for any burn marks etc.
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So when the standby light does come on the TV is able to power on? Check the caps on the power board (2)
из Nvidia
Yes. When the standby light is on, I’m able to turn on the TV and it works perfectly. It never turns off automatically.
из Lionel D