Samsung LN40E550 Dim Screen

[budm]

Re: Samsung LN40E550 Dim Screen

So when I removed the diode and tested resistance across the pads, was the 314 ohms a sign that there may be a bad capacitor?

And when I removed the capacitor and rested the pads and saw the high and climbing resistance (sign of a good capacitor?), was that the next capacitor in the circuit that was causing that?

Then testing the resistance of the capacitor after it was out and seeing it was close to the same ohms as when it was in circuit verified that is the problem?

Please feel free to tell me if I'm completely wrong , I'm just trying to understand some of this.

When you first test the diode that was in place, you were getting the reading in both direction so you have to remove the diode to find out if the Diode is bad or not first, but it is tested OK off the board, then I asked you to check the resistance between the two pads of the removed diode and you found that there is 314 Ohms of resistance between the two pads which is not normal (You have to understand and be able to read the schematic to know why that is not normal), then I have you remove the other diode and it is also tested good off the board, but when you remove that snubber capacitor (it is connected in parallel with the diode) then the resistance between the two pads of the diode went up into high resistance so we then know that it has to be the cap is bad with leakage resistance, which it is. The capacitor is an open circuit to DC but conductive with applied AC, that is why when you check the capacitor with the meter it should show open circuit. Notes: Electolytics cap will show low resistance due to the charging of the cap then it will should show very high resistance because Elecrolytics cap has leakage resistance that is why you see leakage current spec of the lytics caps.

[browserjoe]

Re: Samsung LN40E550 Dim Screen

Thank you for your help and the link to the capacitor info. I will post back when I get the new capacitor in.

[browserjoe]

Re: Samsung LN40E550 Dim Screen

Got the new capacitor today and put it in. TV works again

Thank you budm for all of your help.

[budm]

Re: Samsung LN40E550 Dim Screen

Thanks for the follow-up, glad that it was just a bad cap.

[jettboat]

Re: Samsung LN40E550 Dim Screen

I just found this model in the trash brought it home. Turned it on & all inputs but av were not recognizing, replaced main board (shop jimmy) I now have input (HDMI etc) but screen goes dim then flashes off. P-dim pin 2 on power supply voltage stepped down from power up 3.8 vdc (full bright) to a steady .788 vdc (really dim but not black) screen dimmed each time voltage dropped of course. I checked settings all were up max for BL, lowered to min, now its not going black or flashing is this the main board which controls BL voltage all other pinouts are correct on PS? If so returning SJ board

[budm]

Re: Samsung LN40E550 Dim Screen

Did you try resetting the TV? I think it is 1-8-2-power or something like that, there is a post with collection of rest codes for TVs.
The Dim control signal (and BL-ON, PS-ON) is from the main board.

[jettboat]

Re: Samsung LN40E550 Dim Screen

I tried the reset same issue, then removed the p-dim signal from main board BL is bright & good, I also got constant 4.2 p-dim with usb plugged in so issue is main board. Thanks budm