Samsung UN46EH5300 Backlights turning off and back on

[ThatOneDude]

Hello,

I've got a Samsung UN46EH5300 that is having some backlight problems.

More often than not, everything is fine with it.
Sometimes, the backlight will turn off and then turn back on within three seconds or so.
I have confirmed with the flashlight test that the display is still on and it is the LEDs that are power cycling. I've also seen the LEDs cycle through the vents.

It seems to happen with increasing frequency as the TV heats up.

I took voltage readings at the CNL802 connector with the LED strips connected and disconnected.

Pin Layout
1: D1+ not connected to LED strips
2: D1+
3: S1-
4: S2+
5: nc
6: S2-
7: S3+
8: D1-
9: D1- not connected to LED strips

Readings
LEDs connected and TV powered on
D1 pair (2&8): 68.7 VDC
S2 pair (4&6): 15.76 VDC
D1+ (2) and ground: 110.7 VDC
S1- (3) and ground: 74 VDC
S2+ (4) and ground: 74 VDC
S2- (6) and ground: 57.8 VDC
S3+ (7) and ground: 57.8 VDC
D1- (8) and ground: 39.7 VDC


LEDs disconnected and TV powered on
D1 pair (2&8): 0 VDC
S2 pair (4&6): 0 VDC
D1+ (2) and ground: 200+ VDC
S1- (3) and ground: 0 VDC
S2+ (4) and ground: 0 VDC
S2- (6) and ground: 0 VDC
S3+ (7) and ground: 0 VDC
D1- (8) and ground: 0.75 VDC


Any help would be greatly appreciated, as I'm not really sure where to start and don't want to just throw parts at it.

[budm]

Re: Samsung UN46EH5300 Backlights turning off and back on

Based on the Voltage readings on the LED connector, it looks like you have some shorted out LED. Your TV has 3 strings of LED connected in series to form one big string.
Try setting the backlights level to as low as you can to see if it will run longer.
Also remove the caps CM807, CM811, and CM9841 by the LED connector to see if there is any corrosion or liquid leaking from the legs of the caps or not.
Power supply/LED driver board: Samsung BN44-00667A.
http://www.shopjimmy.com/samsung-bn4...-led-board.htm

LED strips for your LCD panel:Panel Sticker Number: CY-DF460BGLV1H
http://www.shopjimmy.com/samsung-bn9...s-8-strips.htm

D1+is the Anode of the first LED string.
S1- is the Cathode of the first LED string.
S2+ is the Anode of the second LED string and it is connected to the Cathode of the first LED string.
S2- is the Cathode of the second LED string.
S3+ is the Anode of the third LED string and it is connected to the Cathode of the second LED string
D1- is the Cathode of the third LED string which is returned to circuit GND via PWM controlled MOSFET and the current sensing resistor to maintain the constant current through the whole LED string.