Samsung LN55C610

[Rithops]

I have a Samsung LN55C610 which I suspect has a backlight problem. The screen started blacking out sometimes when I turned it on, but could be temporarily fixed by turning it off and back on. Now the screen never lights up.

From what I've read I'm guessing it's a power supply issue, but I'm not sure how to check. The power board is a BN44-00342B. I've checked the voltage on the two large capacitors in the center of the board, and they read about 390V when the power is on. I don't see any obviously failed capacitors. What should I check?

Thanks

[budm]

Re: Samsung LN55C610

Check that white rectangular in the middle of the board right next to the white, verify that the capacitance comes out as printed on the top of the cap, you will have to remove the cap to make the measurement.
It is very commonly failed cap.
https://www.badcaps.net/forum/showth...42B#post546037

[Louis82]

Re: Samsung LN55C610

I have repaired 4 of these tv's by replacing that white capacitor (next to fuse) that budm has mentioned. Also check for any signs of burned or cracked on the thermistor. This is the green color component that looks like a disc, next to your main AC fuse.

[Rithops]

Re: Samsung LN55C610

No visible damage to the thermistor. I don't know a good location around here to have the capacitor checked, so I just replaced it. The screen still stays solid black when I power it on. No on screen display from menu and volume buttons, though the power LED in the corner flickers when I press the button.

Any suggestions? Thanks.

[Rithops]

Re: Samsung LN55C610

Is there anything else I can check to try to get this working?

[budm]

Re: Samsung LN55C610

What type of cap did you use to replace with? That cap is a special type. What is the Value and the Voltage rating did you use?
BTW, do you BL-ON (INVER-ON) signal to this power supply board?

[Rithops]

Re: Samsung LN55C610

For the capacitor, I used a Panasonic ECW-FD2W474J

http://www.digikey.com/product-searc...ywords=pcf1606

I think it's the same as the one you linked, except it's a 5% tolerance (they were out of stock on the 10%).

I also measured the voltages on the 18 pin connector between the main board and power supply. These were measured with the tv on, but the cables to the backlight disconnected (only way I could flip the power supply over). I used a grounding screw as the ground.

1. B13V: 12.9
2. LAMP_DET: 0
3. B13V: 12.9
4. SW_INV: 0.11
5. B13V: 12.9
6. PWM_DIM: Varied
7. GND: 0
8. H_SYNC: 0.04
9. GND: 0
10: GND: 0
11: B5V: 5.2
12: GND: 0
13: B5V: 5.2
14: B5V: 5.2
15. 13/18VS: 18.9
16. A5V: 5.2
17. 13/18VS: 18.9
18. POW_ON/OFF: This pin measured 0.89V, but about every 9s it dropped to 0V, back up to 0.89V, back to 0V, then 0.89V for another 9 seconds.

[budm]

Re: Samsung LN55C610

For the capacitor, I used a Panasonic ECW-FD2W474J

http://www.digikey.com/product-searc...ywords=pcf1606

I think it's the same as the one you linked, except it's a 5% tolerance (they were out of stock on the 10%).

I also measured the voltages on the 18 pin connector between the main board and power supply. These were measured with the tv on, but the cables to the backlight disconnected (only way I could flip the power supply over). I used a grounding screw as the ground.

1. B13V: 12.9
2. LAMP_DET: 0
3. B13V: 12.9
4. SW_INV: 0.11
5. B13V: 12.9
6. PWM_DIM: Varied
7. GND: 0
8. H_SYNC: 0.04
9. GND: 0
10: GND: 0
11: B5V: 5.2
12: GND: 0
13: B5V: 5.2
14: B5V: 5.2
15. 13/18VS: 18.9
16. A5V: 5.2
17. 13/18VS: 18.9
18. POW_ON/OFF: This pin measured 0.89V, but about every 9s it dropped to 0V, back up to 0.89V, back to 0V, then 0.89V for another 9 seconds.

That POW-ON/OFF (PS-ON) should be steady at >2.5VDC so the main board is not sending the steady control signal.
The main board is also not sending the BL-ON (SW_INV) on signal either.

[Redrebel10]

Re: Samsung LN55C610

Hey Budm, since the above readings for PS-On and SW_inv were low, are you suggesting that the main board needs replacing

[Redrebel10]

Re: Samsung LN55C610

I have the same issue, no backlights but I can see an image with the flashlight test and I still have sound. I tried replacing the backlight inverter board but nothing changed. my PS-ON reading is .8v and mu SW_INV reading is 5.1v

[budm]

Re: Samsung LN55C610

Your PS-ON is steady at 0.8V when the TV is turned ON?
If that is the case, then you need to check the DCV between the two legs on either on of the black main filter caps laying on its side to see if it shows around 380VDC of not.
I believe the PS-ON of 0.80V (got new info in later date) is correct for this BN44-00342, the test step above will verify that.

[Redrebel10]

Re: Samsung LN55C610

Yes Bud, with tv powered on the PS_ON holds .8v.

Both of the filter caps hold 395v

[budm]

Re: Samsung LN55C610

Then the PS-ON of 0.80V DC for this power supply/inverter board is OK otherwise you will not have 395VDC Boosted Voltage on the caps.

[budm]

Re: Samsung LN55C610

Common failure for not getting the backlights is due to bad cap, the white rectangular cap right next to the fuse with 2W474K printed on top, look real close to see if it has any bulging sides, you also need to check its capacitance.
Also check that fuse too.

[Redrebel10]

Re: Samsung LN55C610

It has no bulging but I ordered one after seeing you post on another thread. The fuse reads good

thanks Bud

[Redrebel10]

Re: Samsung LN55C610

Hey Bud, got that replacement cap you recommended replacing. There are no markings to suggest a negative side so is the replacement directional or any tips for putting it in correctly?

[budm]

Re: Samsung LN55C610

No polarity on that poly cap.

[Redrebel10]

Re: Samsung LN55C610

Ok thanks

[Redrebel10]

Re: Samsung LN55C610

Happy to report back that I replaced that capacitor and tv is back working, thanks Bud

[budm]

Re: Samsung LN55C610

Thanks for the follow-up.