samsung flashing/flickering/strobing

[zuehls]

I have Samsung UN55ES6150 TS01 tv that has a backlight that flashes/flickers/strobes. I have disconnected the cable between main board and power supply and the backlight stops flashing/flickering/strobing. I checked the voltage on power supply (BN44-00503a) CNL802 pin 4 (R-) and pin 6 (l+) and both are 141v each. It is also steady. If I reattach the cable between main board and power supply and plug in the tv it is steady and good at 141v for about 5-7 seconds and then the screen starts flickering/flashing/strobing and the voltage starts bouncing between 138-142. What is correct voltages on CNL802? Please help troubleshoot. BTW this pattern happens regardless of the input and the image is fine...it just strobes/flashes/flickers.

[neilc6]

Re: samsung flashing/flickering/strobing

Sounds like intermittent/failing LED strips. They are edge lit in this model. What happens when you turn the backlight level down in the picture menu?

[zuehls]

Re: samsung flashing/flickering/strobing

Turning the backlight down to the lowest setting does not have any effect.

By disconnecting the cable between the mainboard and the power supply the problem goes away. Does disconnecting the cable stop the led strips from powering?

Any other thoughts I can test to confirm?

[neilc6]

Re: samsung flashing/flickering/strobing

The main board sends a backlight on (BL-ON) signal to the power supply to turn on the backlights and a PWM signal to dim them. By disconnecting the cable, there is a pull up on the power supply to keep the backlights on. Flickering is a sign of LED failure. Very tricky on large edge lit models to replace the strips.

[budm]

Re: samsung flashing/flickering/strobing

" I have disconnected the cable between main board and power supply and the backlight stops flashing/flickering/strobing." When you perform this self test, the LEDs are driven at max. So the backlights stay on solid without flickering as long as the power is applied to the power supply board? If the LED are going bad then I would expect it to be flickering in self test mode.
Can we see the pictures of the whole backside of the TV showing all the boards?
May be the Dim control signal is varying and causes flickering.

[zuehls]

Re: samsung flashing/flickering/strobing

Pictures attached

[zuehls]

Re: samsung flashing/flickering/strobing

I wanted to provide more feedback for the flickering behavior. After power on AND NO INPUT source connect the following happens:

1. SamsungSmartTV logo flashes on screen
2. Tv presents message that there is 'weak or no signal'. No flickering at this time.
3. After 10 seconds the screen momentarily goes black (like it's sent a command to redraw the screen) and then is starts flickering.
4. If an input source is connected then step 3 does not happen for up to a few minutes before the screen starts flickering. The amount of time it takes varies between 1-4 minutes.

These behaviors regarding the different responses due to the input source is consistent. I've tried all HDMI inputs on the back with the same result.

Hope this helps diagnose.

[budm]

Re: samsung flashing/flickering/strobing

But do the backlights flicker if you do not have main board connected (power supply self test mode) and run it for 5 minutes or more? You indicated it does not flicker in post #1.

[zuehls]

Re: samsung flashing/flickering/strobing

When the mainboard cable is disconnected from the power board I've never seen the backlights flicker. I've had it disconnected for the last 30 minutes and it has not flickered.

[nomoresonys]

Re: samsung flashing/flickering/strobing

Hook everything back up and test pin 2 of connector CNM803 PWM_DIM, power tv on, what is the voltage and is it steady?

[zuehls]

Re: samsung flashing/flickering/strobing

What I did:
1. Reattach mainboard to power board
2. Power on unit
3. Measure pin 2 @ 1.99v (steady) UNTIL screen starts flickering (about 10 seconds). When screen is flickering the voltage fluctuates between 1.79 and 2.2v and it never settles down while the screen is flickering.


1. Power off unit
2. Detach mainboard from power board
3. Turn unit on
4. Measure pin 2 @ 3.13 (steady) never fluctuates

[Diah]

Re: samsung flashing/flickering/strobing

if there at picture setting "local Dimming" turn it off. and check
make hard reset to the TV and check.

[neilc6]

Re: samsung flashing/flickering/strobing

Not sure if this model has an eco sensor option which will adjust the backlight level based on an ambient light sensor. Make sure it is off and restart the tv.

[zuehls]

Re: samsung flashing/flickering/strobing

I've disabled all the eco settings I could find including the following but it has no effect.
energy saving
eco sensor
no signal power off
auto power off

One thing I've noticed is that when I adjust the backlight from 0-20 it does not make any noticeable difference on the screen. Does that point to anything?

[nomoresonys]

Re: samsung flashing/flickering/strobing

All the picture enhancement settings, I just turn off.

[dick_barton]

Re: samsung flashing/flickering/strobing

Does the set have Motion Lighting and if so is it set to ON. If so does turning it OFF stop the flickering

When on, the TV automatically adjusts the brightness of the screen in response to the brightness of the room. In bright light, the screen brightens. In dim light, the screen dims

[budwich]

Re: samsung flashing/flickering/strobing

I've disabled all the eco settings I could find including the following but it has no effect.
energy saving
eco sensor
no signal power off
auto power off

One thing I've noticed is that when I adjust the backlight from 0-20 it does not make any noticeable difference on the screen. Does that point to anything?

what picture mode are you using?

[zuehls]

Re: samsung flashing/flickering/strobing

I've tried all the picture modes, movie, standard, natural, etc.

[budwich]

Re: samsung flashing/flickering/strobing

You might want to try "gentle heating" on the main board at some "key places" and see if that speeds up or slows down the result. Do this with an input since that gives you the "most result" in terms of stability.

[zuehls]

Re: samsung flashing/flickering/strobing

After power on AND NO INPUT source connect the following happens:

1. SamsungSmartTV logo flashes on screen
2. Tv presents message that there is 'weak or no signal'. No flickering at this time.
3. After 10 seconds the screen momentarily goes black (like it's sent a command to redraw the screen) and then is starts flickering.

Can anyone shed light on what could be happening in this sequence to cause the flicker? Is there anything technically happening 10 seconds after the TV message 'weak or no signal' due to no input source being attached that would cause a shift in the stable backlight and causing it to flicker? Why wouldn't it start flickering from go?