Samsung LN46C610N1F no backlight

[Danstona]

I picked up this set from the trash as it looked in good overall health. I found out that the panel is working but no backlight. Upon opening up the rear and inspecting things, reading off of other googled threads, I couldn't immediately find any problems. The fuses are good on the PSU board. The display is there with a flashlight, so the T-Con board seems to be functioning. A deeper scan on the PSU board and I found that CP820, a small blue ceramic disc capacitor is blown out the side. Would just this capacitor be the problem? OR does it indicate a further issue? Board is a BN44-00341B. I was going to try testing a couple things from another thread that I saw budm mention, but I look forward to any responses on this unit issue.

[Danstona]

Re: Samsung LN46C610N1F no backlight

I removed the cable from the PSU to the Main input board and no backlights. I also closely inspected C1818 and it appears good, and gives me a reading of .4688. As common as it seems I guess that is not my issue Hopefully someone with schematics that understands them can tell me if that CP820 is the only issue, I know it let the smoke out, I can smell it on the board! LOL

[budm]

Re: Samsung LN46C610N1F no backlight

CP820 (commonly failed cap, it should be replaced with 2KV cap) is the snubber cap for the PFC DIODE DP802, when the cap is shorted out it will bypass the PFC diode so there will be no boosted Voltage of 380~400VDC on the main filter cap.
What DC Voltage do you have on the main filter cap when TV is turned on?
How about the Voltages on the power suply connector that goes to the main board?
Report the name and the follow by the Voltage readings when TV is OFF and when the power switch is turned on.

[Danstona]

Re: Samsung LN46C610N1F no backlight

Hey budm, glad you could chime in. Could you tell me which is the "main" cap? I will head out to the cold space and test the voltages on the main board connector.

[Danstona]

Re: Samsung LN46C610N1F no backlight

ON is below OFF = all 0.0vdc
PWR_ON/OFF = 12.74vdc
A5V = 12.74vdc
B5V = 5.17vdc
GND = 5.17vdc
GND = 0.0vdc
HSYNC = 0.0vdc
PWM_DIM = 12.74vdc
SW_INV = 12.74vdc
LAMP_DET = 12.74vdc

[budm]

Re: Samsung LN46C610N1F no backlight

You count the pin of the connector wrong that is why those Voltages are wrong, the exposed pins that you can see from the top side are the ODD number pins, the Even number pins you will have to rpbe on the backside of the pins where the wires go into the connector.
The main filter caps are the big lytics cap rated at 450VDC.
The negative leg of the main filter cap is the GND ref. for the primary side of the circuit.
Do not touch anything in the hot side of the circuit, not even the heatsinks.

[Danstona]

Re: Samsung LN46C610N1F no backlight

Wait, so pull the main board plug to test? or pull the board to test?
Testing the main filter caps then with power on? Just test the + side to gnd? This kind of diagnostics is new to me, sorry for the confusion.. I really am capable. Just want to be safe.

[budm]

Re: Samsung LN46C610N1F no backlight

All the boards will have to be connected and live, you will have use skinny probe to test the EVEN number pins though the back side of the connector where the wires go in, chassis GND for your probe because you are working on the cold side of the circuit.
Checking the Voltage between the negative and positive legs of the main cap will be harder since you will be making measurement in the HOT DEADLY side of the circuit.
You should AT THE VERY LEAST plug the AC cord into GFCI outlet TO PROTECT YOUR SELF since I am sure you do not have isolation power transformer.

[Danstona]

Re: Samsung LN46C610N1F no backlight

main filter caps are 75vdc one leg, and 76vdc the other. Thats both 802 and 803.

plug removed to main/ off - on
PWR_ON/OFF = .804vdc - 12.71
A5V = 5.17vdc - 12.71
B5V = 5.17vdc - 5.07
GND = 0.0vdc - 5.07
GND = 0.0vdc - .049
HSYNC = 0.0vdc - .049
PWM_DIM = 5.08vdc - 12.71
SW_INV = 5.08vdc - 12.71
LAMP_DET = 0.0vdc - 12.71

[Danstona]

Re: Samsung LN46C610N1F no backlight

OK sorry that test was with board flipped but main connected.. the long black covered one was not (two small connectors off power board) the main caps are 154.5vdc with everything connected. Reason for flipping that board is that I cannot get my fluke 16 leads into the wire outs to get a reading.

[budm]

Re: Samsung LN46C610N1F no backlight

OK sorry that test was with board flipped but main connected.. the long black covered one was not (two small connectors off power board) the main caps are 154.5vdc with everything connected. Reason for flipping that board is that I cannot get my fluke 16 leads into the wire outs to get a reading.

154.5vdc after the power switch is activated? The PS-ON has to be present for the PFC to work.
Did you remove that blown cap and test the resistance of that PFC diode? You

[budm]

Re: Samsung LN46C610N1F no backlight

BN44-00341B board. This is your board, corrected?
The two main filter caps have two exposed legs so you do not need to flip the board over.
Pictures provided by shopjimmy.

[budm]

Re: Samsung LN46C610N1F no backlight

Can I see the whole backside of the TV showing all the boards?

[Danstona]

Re: Samsung LN46C610N1F no backlight

The board is still intact. The tv made the power on sound and I tested those caps after that. That was my reading..... I remember listening to some sort of youtube video, it was a guy tampatec that said something to the effect that if you get 130vdc its the leds, if 0vdc then the psu board led driver portion is bad and 100vdc then the board leds are bad?


edit:
Yes that is my board. will get photos, 2 minutes.

[Danstona]

Re: Samsung LN46C610N1F no backlight

This is the boards. Lighting isn't great, sorry.

[Danstona]

Re: Samsung LN46C610N1F no backlight

BN44-00341B board. This is your board, corrected?
The two main filter caps have two exposed legs so you do not need to flip the board over.

I only flipped board over to test the other pinout to main input board. I did have to disconnect the wires to what I think is the T-con board in order to flip it. I wont be able to test otherwise unless I can dig up another meter or different leads for my Fluke meter.

[budm]

Re: Samsung LN46C610N1F no backlight

Your TV uses CCFL not LED.
I just watch the 'tampatec' about fixing similar power supply board by cutting the jumper:
https://www.youtube.com/watch?v=i-jQZ-TQdgU
It is easy fix alright by disconnecting the jumper for the PFC Low Voltage protection circuit, instead of find out what the cause of the problem but taking short cut by cutting the wire for protection.
The real problem is due to low PFC Voltage.
I did the circuit analyzing finding out the reason for low PFC Voltage (360V instead of 380~400VDC) is due to bad resistor network in the PFC feedback circuit.
If you look at the pictures of the board, you will see that shopjimmy solder the JP852 back together and fix the PFC circuit.
Be careful as to what you see on Youtube!

[attainteddragon]

Re: Samsung LN46C610N1F no backlight

use a thin piece of wire, like a resistor or cap leg to poke into the connector to save having to disconnect anything. it is slow, but it will work.

[budm]

Re: Samsung LN46C610N1F no backlight

At this point we need to get that PFC boosted Voltage of 380 (at least)~400V first.
So verify again the Voltage reading between the + and - leg of either one of the main filter cap when power switch is activated, the backlights inverter circuit needs that Voltage to run.

[Danstona]

Re: Samsung LN46C610N1F no backlight

Ok, I appreciate your help. I have run out of time this evening to test. I will look for another set of leads (thought I bought replacements) if not I have a cheaper handyman meter somewhere too. Just to confirm, I have NOT replaced/repaired the CP820 Capacitor yet. I am also bench testing the tv with no stand so its hard to know when its on or off without flipping over. (red LED on means off, and LED off means tv ON?) Tomorrow when I get a chance I will repost with voltages ON and OFF from pinout on main board connector from PSU, as well as double check the main filter caps voltage. Perhaps I can find a cap locally so I dont have to wait on digikey and pay shipping. Talk soon!