Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

[DeatRaton]

Long story short guys, I was getting crazy readings on backlights from LED driver. Opened the tv up and found almost 1 to 2 bad leds on each strip. Purchased brand new LEDs, replaced all backlights.
Still no luck. At this point I unplugged Main board connector from power supply assuming if I had a bad main board the LEDs would actually light up and no luck. Does this mean power supply needs to be replaced?

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Check the voltage on CNL802 pin1 then check the voltage on pin12. You will need to have your probe on the pin when the tv is first turned on as the led supply will go into shutdown.
All strips are in series so check their interconnections.
Also what do you mean by purchased brand new leds? New led strips or did you replace the led's ON the strips.

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I replaced the LED strips, with brand new ones.

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

were the strips the same as the originals? IE 30055A or 30056A as there seems to be different strips for this model
what about the voltage on CNL802

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights


CNL-802 Pin 1
On-216v

CNL-802 Pin 12
On- 62V

[neilc6]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Bad LEDs can damage the power supply on Samsung models. Check for shorts on the power diodes in that section (all along the left in your picture). Looks like a replacement board is only around $30 on ebay. Your part number in BN44-00774A.

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

These were the ones I purchased were exactly the same as the ones on my TV as far as style and placement.

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

So quick question. I'm supposed to get stand by reading of 8v? I cannot get a read in on that, on the diagram my power supply it point to a small dot and I get no reading from putting my tester end in that slot.

One more thing is the readings on my power supply connection to main board are not matching the chart but as soon as I remove the main board connection all the readings are back to normal.

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Seems like the voltage on pin 1 is Low, It should be around +268v. Check this voltage when the tv is first pluged in and turned on. I suspect it comes up then drops down. It could be low because the power supply is not being turned on with the PS_ON command from the main board.

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

So quick question. I'm supposed to get stand by reading of 8v? I cannot get a read in on that, on the diagram my power supply it point to a small dot and I get no reading from putting my tester end in that slot.

One more thing is the readings on my power supply connection to main board are not matching the chart but as soon as I remove the main board connection all the readings are back to normal.

What do you mean :" I cannot get a read in on that" Are you getting 0 volts?
Do you have A13v ?
what is the voltage on PS_ON (J833)? Does this voltage change when the power button is pressed?

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

TV off.

Stb: 0.
Od/ud: 11.8
Blu_pwm:11.8
Ps on: 11.8
Gnd: 11.8
Gnd: 0

Tv on
Od/ud: 12.78
Blu_pwm: 12.78
Ps on: 12.78
Gnd. 12.78
Gnd 0

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Those 12.78v are pins 1,3,5,7 GND is pin10. There are two rows onf pins on CNM803. Check the voltage on pins 2,4 and 6. with the tv OFF then ON
J833 connects to the PS_ON pin4
J832 (STB:8V↑) connects directly to pins 1,3,5,7 of cnm803 (it does NOT connect to the hole above the ↑)

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

TV off
OD/ UD : 3.3V
BLU_PWM: 3.3V
PS ON : 3.3V

Powered on it has the same readings nothing changes.

J832 TV off 11.8V
J832 TV on 12.8V

Thank you for your help. I'm barely learning

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

If the BLU_PWM and the PS_ON stays at 3.3 volts, what is telling you the tv is actually turning ON and OFF? Those voltages should change.
If the tv is indeed turning on and the backlight is not, you should be able to see the picture on the screen using a flashlight, you should also have the source audio. You may need to press the menu to see anything on the screen if you have no source connected.

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Yea I do have image on the screen, I actually included a picture on my first post up top of the menu. That's why I had assumed it was the LED Strips from the start

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I did'nt look that close at the picture, One thig to check is the voltage across the main filter cap CP810S, This voltage should be around 160vdc in standby but will increase to around 380vdc when the tv is on. If this pfc voltage is low, that could explain the low led voltage
I would also check the value of R9162, it is in the led return line and R9161
It seems like Q910c is not boosting the led voltage from 210 to 268v, You can try unpluging CNL802, then monitor the voltage at test point CH1, with no led load this voltage should come up to around 300vdc when the tv is first turned on, the detect an open circuit and the voltage will drop to around 210v

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

TV Turned off
CP810S
164V

CR810S
391V

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

If that 391V is across CP810S then the pfc is working ok. Try the other test in post 16 (I edited)

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

With CNL802 unplugged CH1 got up 217V upon turning the TV on, and it remained at 217V. I plugged CNL802 back in and did the same thing and upon turning the TV on CH1 had the same readings. Reached 217V and it remained at that voltage.

I see R9162 but not sure if I am testing it right. I have positive on one side and negative on the other side. Is that correct if so I am getting no readings.

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Edited last message with more info