Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

You need to check the resistance of R9162 and R9161 (done with power supply disconnected from ac)
It is hard to tell from the picture but I think R9162 is 27Ω, R9161 is 0.3Ω

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

As far as the LED drive on the supply board. Is it normal to get readings on CNL802 of
M1+ 217V
M2+. 185V
M3+. 154V
M4+. 123V
M5+. 92V

I may be really wrong but aren't these usually the same Voltage across the board or is this fine?

R9162- 2.2
R9161- 0.8

[budm]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Are those readings with LED connector in place or not in place?
Put the LED connector in placeDid you leave the black probe on the chassis and Red probe on M1+ then turn on the TV while watching the meter to see if the Voltage jumps up > 217?
What do you get on M1- when you move the red probe to M1- and then turn on the TV?
Based on your readings (if the LED connector is in place), it shows that M1 LED string has open circuit.
The LED strings are connected in series to form one large LED string.
M1+ the Anode of the first LED string that is fed by the LED power supply boost converter output, M1- is the Cathode of the LED #1 string, this cathode is then connected to the M2+ (Anode) of the #2 LED string, the M2- (Cathode) is connected to the M3+ (Anode) of the #3 LED string , and so on and on.

Samsung BN44-00774A
https://www.shopjimmy.com/samsung-bn...led-board.htm#

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

If those voltages were normal you would have your backlights, The M1+ is the main led supply to the first string, It should be +268 volts.
The difference between M1+ and M2+ is 32 volts, that line feeds one string of 14 led's so each led on the string is getting aprox, 2volts (I would guess they are lit but very dim) As you can see, each strinig is supplied by aproximately 30 volts, that is not enough voltage to light the led's, as each led needs around 3 volts
The diodes (DM841,2,3,4C) off of TM801CS transformer supply the base +217 volts and is filtered by CM841.
This voltage is feed through T9101C. It then needs to be BOOSTED by Q9101C to +268 volts. (similar to the pfc boost circuit) Q9101C is driven by IC9101, So it is possible IC9101 has a problem
Post the number of IC9101 so we can check to see if it has VCC etc. It might be a SEM5027

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Are those readings with LED connector in place or not in place?
Put the LED connector in placeDid you leave the black probe on the chassis and Red probe on M1+ then turn on the TV while watching the meter to see if the Voltage jumps up > 217?
What do you get on M1- when you move the red probe to M1- and then turn on the TV?
Based on your readings (if the LED connector is in place), it shows that M1 LED string has open circuit.
The LED strings are connected in series to form one large LED string.
M1+ the Anode of the first LED string that is fed by the LED power supply boost converter output, M1- is the Cathode of the LED #1 string, this cathode is then connected to the M2+ (Anode) of the #2 LED string, the M2- (Cathode) is connected to the M3+ (Anode) of the #3 LED string , and so on and on.

Samsung BN44-00774A
https://www.shopjimmy.com/samsung-bn...led-board.htm#

M1- is getting a 185V
Yes I have the black probe on the chasis and red on the pins.

And yeah those readings are with the LED connector. When the connector is off I get 217V on M1+

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

If those voltages were normal you would have your backlights, The M1+ is the main led supply to the first string, It should be +268 volts.
The difference between M1+ and M2+ is 32 volts, that line feeds one string of 14 led's so each led on the string is getting aprox, 2volts (I would guess they are lit but very dim) As you can see, each strinig is supplied by aproximately 30 volts, that is not enough voltage to light the led's, as each led needs around 3 volts
The diodes (DM841,2,3,4C) off of TM801CS transformer supply the base +217 volts and is filtered by CM841.
This voltage is feed through T9101C. It then needs to be BOOSTED by Q9101C to +268 volts. (similar to the pfc boost circuit) Q9101C is driven by IC9101, So it is possible IC9101 has a problem
Post the number of IC9101 so we can check to see if it has VCC etc.

C9101 if hats what you meant had 217V

[budm]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

M1- is getting a 185V
Yes I have the black probe on the chasis and red on the pins.

And yeah those readings are with the LED connector. When the connector is off I get 217V on M1+

But I thought they are .xxx V FOR 2 ~ 5.
M1+ 217V
M2+. 185V
M3+. 154V
M4+. 123V
M5+. 92V
So they are actually 185V, 154V, 123V, and 92V.
The key point is that the probes must be in place before turning on the TV, if that is what you did then the boost converter is not working as RJ suggested.

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

C9101 if hats what you meant had 217V

Have you had a look at the back of the board ? Q9101 is the FET that BOOSTS the raw 217 volts to 268 volts
I am gussing that CM888 is the Vcc supply filter cap. for the sop16 driver ic, check the voltage on J840 (ic9101 vcc) should be +13volts

[budm]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I would check boost converter diode D9101 also.

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I would check boost converter diode D9101 also.

D9101 gave me 217V reading

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Have you had a look at the back of the board ? Q9101 is the FET that BOOSTS the raw 217 volts to 268 volts
I am gussing that CM888 is the Vcc supply filter cap. for the sop16 driver ic, check the voltage on J840 (ic9101 vcc) should be +13volts

The voltage on J840 was 12.75volts
And the FET Q9101 gave me a reading of 217v

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I know you only have 217v on Q9101. Thats because that BOOST circuit is NOT working.
Check that D9101 is not shorted using diode test.
The drive ic is getting vcc so it could be that the ic is bad, or more likely the ic is in protection.
Are you sure the voltage on M1+ NEVER reaches 268 volts. You need to have the meter ON that point when the tv is first pluged in and turned on. If there is any error in the led current or voltage, the ic will shut down the boosted voltage within 1/2 a second and all you will read is the 217v.
Also check if you have the backlight ON voltage at the ic itself

[DeatRaton]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I included a picture of the diode reading I got.

And no M1+ goes up to 217 max, it creeps its way up to 217v its not an instant jump to 217 and never goes above that at any point. Not when its plugged in with negative on chasis and positive on M1+ pin before plugged in. When turned on as well only up to 217.

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Ok so the diode is ok. so the problem seems to be with the led driver/boost circuit, (whatever the ic is) is likely damaged but for now check that Q9101C is not shorted, also check Q9102C to make sure it is not shorted.

[budm]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

"And no M1+ goes up to 217 max, it creeps its way up to 217v"
It sounds to me that your HF meter is too slow for the fast rising of the power supply Voltage. I do not expect the Feeding Voltage that feeds the boost converter to rise up slowly.

[R_J]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

I would try checking that M1+ voltage without the led's connected, If the boost voltage IS there it should charge C0131 to the full 268v before discharging

[x-solja]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Hey All, not to highjack the thread, but I have the same TV, and have no backlights showing up as well.... I have been following along and testing as mentioned, however I do not get a hard set value when checking the M1+, or even the D9101.

With CNL802 connected and TV powered up, I see constant changing values:
M1+: 320, 311, 302, 293, 285 then back up to around 316, and back down through the same process.
D9101 does the same similar process where it will jump all over the place up to 400, then huge drops down after that and just keeps looping around.

I also notice when checking the lines across CNL802 (besides the varying voltages across each point), when I get to M9+ its showing 0V from then on...

Any ideas, or more things to check? ...or is this a clear sign my Power is bad?


Thanks,

-X-

[x-solja]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Correction to the above... By M9+ i mean the 9th pin and M4+


To add to the above, i found that if I bridge M4+ to M5- the leds will come on and everything works. ...So, i guess that would mean I have an issue with my M4/M5 led line

[nomoresonys]

Re: Samsung UN55J6201AFXZA Powers On+ Image but No Backlights

Any progress or update on this one DeatRaton?