Samsung un55js7000 no power

[Foofles]

Hey.

So, the tv seems to come on apart from the backlight. I can hear clicks through the speakers as I press menu buttons.

The power supply board is labeled bn44-00859a. The voltages from the backlight connector are < 1 volt. There seems to be a damaged coil on the board.... At least I think it's a coil. Labeled LP802CS. Seems to have holes melted on one side!

Should I try replacing just this one component? It doesn't have any markings that Google will find, so I'm not sure how to even get another one.

Board and damaged component pictures are attached. Any help is much appreciated.

[budm]

Re: Samsung un55js7000 no power

Hey.

So, the tv seems to come on apart from the backlight. I can hear clicks through the speakers as I press menu buttons.

The power supply board is labeled bn44-00859a. The voltages from the backlight connector are < 1 volt. There seems to be a damaged coil on the board.... At least I think it's a coil. Labeled LP802CS. Seems to have holes melted on one side!

Should I try replacing just this one component? It doesn't have any markings that Google will find, so I'm not sure how to even get another one.

Board and damaged component pictures are attached. Any help is much appreciated.

Those are PFC inductor, doubt that they are bad, you will not have PFC Boost Voltage of 380 ~ 400VDC on the main filter caps when PS-ON is present, you can easily verify that..
1) Remove the cable between main board and the power supply and inspect both ends of the cable, male pins of both board where the cable is plugged into.

2)You need to report the Voltage reading of the connector of the power supply board that goes to the main board when TV is plugged in and when power switch is activated.
The connector has pin names to tell you what each pins are for, so make sure the count the pin correctly since they are arranged in EVEN and ODD column pins per chart as printed on the board.
The format should be like this for example:

Pin x, name of the pin, reading when TV is plugged in, reading when power switch is activated so we can easily see what we have and do not have.

[budm]

Re: Samsung un55js7000 no power

....

[dick_barton]

Re: Samsung un55js7000 no power

What dc voltage do you have between any one of the two legs of the 60uF, 500V capacitors.

[Foofles]

Re: Samsung un55js7000 no power

Thanks for the replies.
The connector to the main board reads the proper voltages. The label says it should have four pins with 13v. I read 12.6ish on them.

The 500v 60uf caps near the inductor all read 391v.

[dick_barton]

Re: Samsung un55js7000 no power

So it looks like the PFC voltage is working since you have 390V.

Can you post the voltages on the power supply.....connector pin, name and voltage.

eg
Pin 1  STB   +5V
Pin 2  P_ON  +3.5V

You may be missing a voltage from the mainboard or have a problem with the led(s) but without voltage readings its difficult to identify any fault.

[Foofles]

Re: Samsung un55js7000 no power

I'm not sure what connector you want me to check. The one going to the main board seems okay, but the one going to the LEDs is not.

[budm]

Re: Samsung un55js7000 no power

I'm not sure what connector you want me to check. The one going to the main board seems okay, but the one going to the LEDs is not.

What do you mean 'seems OK'?

What are the Voltages on each one of those pins?

[Foofles]

Re: Samsung un55js7000 no power

The pinout is attached.
I measured each of the pins that are labeled with a voltage, and they're correct. Do I need to measure the others?

[budm]

Re: Samsung un55js7000 no power

CNM803 connector.

Pin 1 (Fail Count):: TV OFF = ????V, TV ON = ????? V
Pin 2 (ANA DIM.): TV OFF = ????V, TV ON = ????? V
Pin 4 (OD ON/OFF): TV OFF = ????V, TV ON = ????? V
Pin 6 (PWM_BLU): TV OFF = ????V, TV ON = ????? V
Pin 8 (POWER ON): TV OFF = ????V, TV ON = ????? V

[Foofles]

Re: Samsung un55js7000 no power

CNM803 connector.

Pin 1 (Fail Count):: TV OFF = 3.23V, TV ON = 3.24 V
Pin 2 (ANA DIM.): TV OFF = 3.332V, TV ON = 3.331 V
Pin 4 (OD ON/OFF): TV OFF = 3.295V, TV ON = 3.293 V
Pin 6 (PWM_BLU): TV OFF = 2.785V, TV ON = 2.778 V
Pin 8 (POWER ON): TV OFF = 3.313V, TV ON = 3.314 V

PWM_BLU varied sightly. Was .2v higher when I tested the first time. But yeah... No changes from being on vs off.

[budm]

Re: Samsung un55js7000 no power

Pin 1 (Fail Count):: TV OFF = 3.23V, TV ON = 3.24 V. I do not know exactly this pin is for.

Pin 2 (ANA DIM.): TV OFF = 3.332V, TV ON = 3.331 V. This is the receiving pin for backlights Analog Dimming control signal from main board. it will vary with Backlights level setting. More then likely that this TV does not use this signal, it probably use the PWM.

Pin 4 (OD ON/OFF): TV OFF = 3.295V, TV ON = 3.293 V. This is the receiving pin for the BL-ON Backlights ON/OFF control signal form main board, <1V = OFF, >2V = ON, so when TV is OFF it should be <1V.

Pin 6 (PWM_BLU): TV OFF = 2.785V, TV ON = 2.778 V. This is the receiving pin for backlights PWM Dimming control signals from main board. it will vary with Backlights level setting.

Pin 8 (POWER ON): TV OFF = 3.313V, TV ON = 3.314 V. This is the receiving pin for Main Power supply control signal from main board. it should be <1V when TV is OFF, >2V when TV is on.

Are you measuring these pins with all the connectors in place?

[Foofles]

Re: Samsung un55js7000 no power

Are you measuring these pins with all the connectors in place?

Yeah. Everything is connected.

I should note that I hear the relay near the power plug click on a second or two after plugging it in. It seems to be turning itself on... I swear it wasn't doing this when I was testing the other day.
It is < 1v for the brief moment before I hear the relay click

Edit - the relay clicks when I plug it in even with the main board disconnected

[budm]

Re: Samsung un55js7000 no power

Well, I hope you do not have two problems.
1: the Backlights do not come on.
2: the main board POWER ON (PS-ON) and OD ON/OFF (BL-ON) are stuck high.

The board has Pull -up resistor to simulate the POWER ON (PS-ON) signal for power supply board self test. To find out if it has other pull-up resistors for other control pins, you need to test the those pins again without cable to the main board connected then we can try fixing the backlights first.

[Foofles]

Re: Samsung un55js7000 no power

To find out if it has other pull-up resistors for other control pins, you need to test the those pins again without cable to the main board connected then we can try fixing the backlights first.

With main board disconnected-

Fail count .8v
Ana dim 3.2
Od on off 3.6
Pwm Blu 3.6
Power on 4.5

[budm]

Re: Samsung un55js7000 no power

With main board disconnected-

Fail count .8v
Ana dim 3.2
Od on off 3.6
Pwm Blu 3.6
Power on 4.5

So they do have built-in pull-up resistors to perform stand alone power supply /LED driver board test.

As you report in your post #5 that you do have 391VDC on the main filter cap, so PFC Boosted Voltage circuit is working fine.

So now we need to find out why the backlights do not come on and stay on as long as the board is plugged into the AC outlet.

https://www.badcaps.net/forum/attach...5&d=1597799898

The picture is too blur and too dark for me to read any prints on the board, I also need closed up pictures around the LED connector so I can see how many wires it has on the connector, and also need the straight shots of the whole bottom side of the power supply board, BN44-00859A.

[Foofles]

Re: Samsung un55js7000 no power

The picture is too blur and too dark for me to read any prints on the board, I also need closed up pictures around the LED connector so I can see how many wires it has on the connector, and also need the straight shots of the whole bottom side of the power supply board, BN44-00859A.

The led connector has four wires. It's disconnected in the attached pictures. The soldered on wires are coming from the main board connector.
Edit - 16 total pins on the led connector, but only 4 are used.

[Foofles]

Re: Samsung un55js7000 no power

Here's a better picture of the bottom of the led connector. The big caps near it had 390ish voltage.

[neilc6]

Re: Samsung un55js7000 no power

Samsung smart tvs will remember their last state so if it was on and the plug was pulled, they will power up on automatically when plugged in again.

I would guess you have bad backlights but I will let budm guide you through the troubleshooting process.

[Foofles]

Re: Samsung un55js7000 no power

Samsung smart tvs will remember their last state so if it was on and the plug was pulled, they will power up on automatically when plugged in again.

I would guess you have bad backlights but I will let budm guide you through the troubleshooting process.

That would explain why it acted differently the first time I plugged it in!