Need help with Samsung LN40E550f7f

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

http://www.shopjimmy.com/samsung-bn4...upply-unit.htm look closely is this your power supply?

[budm]

Re: Need help with Samsung LN40E550f7f

psb:
1. B13V -13.1V

2. DIM- 5V

3. B13V-13.1V

4. NC -0V

5. B13V- 13.1V

6.BLU_ON -0V

7. B13V-13.1V

8., 9., 10 GND- 0V

11.B5V- 5.1V

12 A5V - 5.1V

13. B5V- 5.1V

14. PS_ON- 3V

You have the correct Voltages but it is missing the BL-ON signal from the main board to turn on the backlights circuit, the power supply board may have pull-up resistors for the control signals pins to allow self test of the power supply board, do unhook the cable from the power supply board to the main board then pug the TV into the outlet to see if the backlights will come on and stay on as long as the TV is plug in or not.
If the backlights do not come on then you need to report the Voltage readings on that connector of the power supply board again (without it connecting to the main board), the reading will tell us if the power supply board has pull-up resistors or not.

[freakaftr8]

Re: Need help with Samsung LN40E550f7f

You have any dark lines spanning horizontally in the screen?

Just fixed one of these suckers the other night. 3 bad CCFL tubes. Usually represented with picture may or may not come on briefly but you can see with a flashlight. This model probably has pull up resistors so the CCFLs will come on if you disconnect the main board from the power supply.

If it does not look towards an inverter or CCFL failure.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Don't have a schematic, not sure if this one will do it, try unplug power supply board from main board, see if backlights go on.

It does not.

[budm]

Re: Need help with Samsung LN40E550f7f

BTW, your power supply board is not the typical power supply-inverter combo board.
The board has the Inverter transformer driver circuit with MOSFETs on the power supply board, they supply high frequency AC to connector CNI801 pin 3 (LOW 193VAC) and pin 1 (HIGH 373VAC) of the power supply board to drive the Primary winding of the Inveter transformers on the Inverter transformer board, CNI801 also supplies 12VDC (which you report as present) to run the protection circuit on the Inverter transformer board.

[budm]

Re: Need help with Samsung LN40E550f7f

It does not.

Please check the DC Voltages on those connector pins again (without the cable going to the main board in place), the readings will tell us if it has pull-up resistors for self test or not.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

No scorch marks. 450v caps read 375v. Everyone is talking about standby mode; on this t.v. , when is off, the indicator light stays red and I have no readings. If I turn it on, it chimes, the light flashes and then goes off. After several minutes, it shuts off.

I have a ln40c650, seems like normal operation is solid red standby light while off , when I turn it on I get 5 blinks then it goes off, the standby light that is. seems to be working fine.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

You have any dark lines spanning horizontally in the screen?

Just fixed one of these suckers the other night. 3 bad CCFL tubes. Usually represented with picture may or may not come on briefly but you can see with a flashlight. This model probably has pull up resistors so the CCFLs will come on if you disconnect the main board from the power supply.

If it does not look towards an inverter or CCFL failure.

I think you are right Freak.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

https://www.youtube.com/watch?v=Z1DEkSguWtg testing boards and troubleshooting.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

https://www.youtube.com/watch?v=Z1DEkSguWtg testing boards and troubleshooting.

He's on an led tv there, not exactly the same as an lcd, good info tho.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

http://www.shopjimmy.com/cmo-27-d070...t-inverter.htm probably time to test inverter, you have two right, so if they both test the same, they might both be good. then it's looking more like a bad ccfl/lamp.

[budm]

Re: Need help with Samsung LN40E550f7f

"6.blu_on -0v"

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

I think you are right Freak.

Nice fix btw, bet it was a tough to get done without breaking anything.

[Kindred1]

Re: Need help with Samsung LN40E550f7f

Sorry all,..internet went down again yesterday all afternoon and night. Grrr. Back at it now. Reading through my responses.

[freakaftr8]

Re: Need help with Samsung LN40E550f7f

Yea but at least it was only a 40 inch. Try removing an LCD from a 75 or 80 inch by yourself. Smh.

The one I worked on had a constant blu-on so maybe this one could be inverter related.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

Ok not sure but is this the type you can jump ps on blu on and standby together to start up the power supply board?

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

So if you jumper blu on and standby the backlights should go on and stay on, correct?

[Kindred1]

Re: Need help with Samsung LN40E550f7f

You have the correct Voltages but it is missing the BL-ON signal from the main board to turn on the backlights circuit, the power supply board may have pull-up resistors for the control signals pins to allow self test of the power supply board, do unhook the cable from the power supply board to the main board then pug the TV into the outlet to see if the backlights will come on and stay on as long as the TV is plug in or not.
If the backlights do not come on then you need to report the Voltage readings on that connector of the power supply board again (without it connecting to the main board), the reading will tell us if the power supply board has pull-up resistors or not.

Backlight does not come on. Voltages:

1. B13V -13.1V

2. DIM- 5.01V

3. B13V-13.1V

4. NC -0V

5. B13V- 13.1V

6.BLU_ON -0V

7. B13V-13.1V

8., 9., 10 GND- 0V

11.B5V- 5.18V

12 A5V - 5.18V

13. B5V- 5.18v

14. PS_ON- 3.07

[Kindred1]

Re: Need help with Samsung LN40E550f7f

You have any dark lines spanning horizontally in the screen?

Just fixed one of these suckers the other night. 3 bad CCFL tubes. Usually represented with picture may or may not come on briefly but you can see with a flashlight. This model probably has pull up resistors so the CCFLs will come on if you disconnect the main board from the power supply.

If it does not look towards an inverter or CCFL failure.

No, nothing on screen.

[nomoresonys]

Re: Need help with Samsung LN40E550f7f

https://www.youtube.com/watch?v=n54IurMvr6o here's a video explaining the jumper procedure.