Samsung LN46C600F3FXZA - No backlight

[SurrealMustard]

I'm working on this Samsung L46C600F3F LCD which works, but isn't lighting up the backlight. Does anyone know of a good place to start troubleshooting this? Would the readings from the connector described in this other thread be a good place for me to start?

[Hamie]

Re: Samsung LN46C600F3FXZA - No backlight

Does the power supply get the BL-ON signal from the mainboard?

Upload some pics.

[SurrealMustard]

Measurements

Does the power supply get the BL-ON signal from the mainboard?

Upload some pics.

I'm not completely sure. Here's what I've got for measurements from the connection between the power supply and the mainboard (most of these look to be on par with the little chart, as pictured):

1. 12v
2. 0
3. 12v
4. 5v
5. 5v
6. 5v
7. 5v
8-11. Ground
12. 1v
13. 12v
14. 1v
15. 12v
16. 5v
17. 12v
18. 0

If it helps, I also measured the CN1802, which connects the power supply to the inverter. I got 12v on pin 1 and 9v on pins 6 and 7. Turning on the power with the mainboard disconnected from the power supply (as suggested in the other LN46C600F4FXZA thread) does not elicit a response either.

[budm]

Re: Samsung LN46C600F3FXZA - No backlight

You need to put the name of the next to the pin number so we will know what each pin is.
That thread in the link you post is a good thread to follow, since that cap is the commonly failed cap I would check its capacitance, or see if it has bulging to the side.

[SurrealMustard]

Results with definitions

You need to put the name of the next to the pin number so we will know what each pin is.

Here are the voltages with the pin names, going by the printout on the board next to the connector:

1 (B18VS). 12v
2 (SW_POWER). 0v
3 (B18VS). 12v
4 (A5V). 5v
5 (B5V). 5v
6 (B5V). 5v
7 (B5V). 5v
8 - 11 (GND). Ground
12 (FRC_HSYNC). 1v
13 (B13V). 12v
14 (PWM_DIMMING). 1v
15 (B13V). 12v
16 (SW_INVERTER). 5v
17 (B13V). 12v
18 (DET_5V). 0

That thread in the link you post is a good thread to follow, since that cap is the commonly failed cap I would check its capacitance, or see if it has bulging to the side.

I don't have a tool with which to do capacitor testing and they all look fine to me. Would the inverter be a possible culprit as well or should I focus more on the power supply board?

[budm]

Re: Samsung LN46C600F3FXZA - No backlight

OK, your pinout and the names are way off as printed on the board (BN44-00341B).
I.E.
Pin 1 = B13V
Pin 2 = LAMP_DET
.....
......

BTW, the exposed pins on the top side are the ODD NUMBER pin, the EVEN NUMBER PINS are on the bottom side of the board. The white triangle is pin 1.

POST 3
I'm not completely sure. Here's what I've got for measurements from the connection between the power supply and the mainboard (most of these look to be on par with the little chart, as pictured):

1. 12v
2. 0
3. 12v
4. 5v
5. 5v
6. 5v
7. 5v
8-11. Ground
12. 1v
13. 12v
14. 1v
15. 12v
16. 5v
17. 12v
18. 0

Post 5:
Here are the voltages with the pin names, going by the printout on the board next to the connector:

1 (B18VS). 12v
2 (SW_POWER). 0v
3 (B18VS). 12v
4 (A5V). 5v
5 (B5V). 5v
6 (B5V). 5v
7 (B5V). 5v
8 - 11 (GND). Ground
12 (FRC_HSYNC). 1v
13 (B13V). 12v
14 (PWM_DIMMING). 1v
15 (B13V). 12v
16 (SW_INVERTER). 5v
17 (B13V). 12v
18 (DET_5V). 0

[SurrealMustard]

I see

OK, your pinout and the names are way off as printed on the board (BN44-00341B).
I.E.
Pin 1 = B13V
Pin 2 = LAMP_DET
.....
......

BTW, the exposed pins on the top side are the ODD NUMBER pin, the EVEN NUMBER PINS are on the bottom side of the board. The white triangle is pin 1.

POST 3
I'm not completely sure. Here's what I've got for measurements from the connection between the power supply and the mainboard (most of these look to be on par with the little chart, as pictured):

1. 12v
2. 0
3. 12v
4. 5v
5. 5v
6. 5v
7. 5v
8-11. Ground
12. 1v
13. 12v
14. 1v
15. 12v
16. 5v
17. 12v
18. 0

Post 5:
Here are the voltages with the pin names, going by the printout on the board next to the connector:

1 (B18VS). 12v
2 (SW_POWER). 0v
3 (B18VS). 12v
4 (A5V). 5v
5 (B5V). 5v
6 (B5V). 5v
7 (B5V). 5v
8 - 11 (GND). Ground
12 (FRC_HSYNC). 1v
13 (B13V). 12v
14 (PWM_DIMMING). 1v
15 (B13V). 12v
16 (SW_INVERTER). 5v
17 (B13V). 12v
18 (DET_5V). 0

You know, I was looking at that and thought I had them the right way, but that was apparently not the case.

Given that we've figured out the correct values now, do you think are they on the right track for what the power supply should be putting out? All the names that have numbers in them closely match the actual voltage, so am I right in my assumption that everything on the power supply looks okay based on this? Would the inverter board be the more likely culprit?

[budm]

Re: Samsung LN46C600F3FXZA - No backlight

No, that readings with the name and pin numbers are wrong.
For example, pin 18 of the board is PWR-ON/OFF, you show pin 18 reading of 0V, that means the PS-ON is not present to turn on the power supply board.
Pin 7 you show that it has 5V which will be impossible since pin 7 is GND,
PIN 7, 9, 10, 12 are ground pin. You have "8 - 11 (GND). Ground"

You should take the Voltage readings again with correct pin names and numbers.
Without correct readings then we cannot tell what is going on.

[SurrealMustard]

Fixed

As suspected, the power supply was indeed the culprit.

Fixed!