Hi, I have a Samsung LA55B650T1F tv which died i.e. the red standby light went off when turning it on and it never came on again. I've disconnected the AC and left it overnight and reconnected it. Upon pwr on, it doesn't come up. I can sometimes see the leds on the ethernet connector flicker faintly on/off and then nothing.
So, after opening up the tv, I did a visual inspection of the power board, connectors etc. All looked ok. I have checked all the electrolytes with an ESR meter and checked their capacity out of circuit and they are fine.
When disconnecting CN801 between power board (BN44- 00268A) and the main logic board and then plugging in power, the back leds flash on/off twice and then stay on permanently.
Measuring voltages on CN801 is as follows NOTE (Missing pins are not connected):
AC PWR Plugged In
1 - PS = 0v
2 - Sync = 0v
3 - SB = 5.22v
5 - GND = 0v
7 - 18v = 0v
9 - GND = 0v
11 - GND = 0v
13 - 5.1v = 0v
15 - 5.1v = 0v
17 - GND = 0v
19- 13v = 0v
21 = 13v = 0v
23 - INV-ON = 0v
25 - E-PWM = 0v
27 - 5V-DET = 0v
29 - GND = 0v
30 - GND = 0v
AC PWR Plugged In with CN801 Disconnected and led lights on (Led light flashes twice on/off and then stays on permanently.)
1 - PS = 0.78v
2 - Sync = 0v
3 - SB = 5.22v
5 - GND = 0v
7 - 18v = 18v
9 - GND = 0v
11 - GND = 0v
13 - 5.1v = 5.22v
15 - 5.1v = 5.22v
17 - GND = 0v
19- 13v = 12.43v
21 = 13v = 12.43v
23 - INV-ON = 3.8v
25 - E-PWM = 4.95v
27 - 5V-DET = 5.21v
29 - GND = 0v
30 - GND = 0v
AC PWR Plugged In, all cables plugged and pwr on via remote
1 - PS = fluctuating 0.5 - 0.7v
2 - Sync = 0v
3 - SB = fluctuating 0.6 - 2.4v
5 - GND = 0v
7 - 18v = fluctuating 5 - 12v
9 - GND = 0v
11 - GND = 0v
13 - 5.1v = fluctuating 0.6 - 2.2v
15 - 5.1v = fluctuating 0.6 - 2.2v
17 - GND = 0v
19- 13v = fluctuating 1.90 - 5.80v
21 = 13v = fluctuating 1.90 - 5.80v
23 - INV-ON = fluctuating 0.1 - 1v
25 - E-PWM = fluctuating 0.2 - 2.3v
27 - 5V-DET = 0v
29 - GND = 0v
30 - GND = 0v
I've also tried disconnecting everything from the main board, except the CN801 pwr cable and it still causes the fluctuation of the voltages.
I'm thinking the power board is ok, but the main board may have a problem. It would appear it's loading one of the supplies off the power board and then retrying to power it up again in a cyclic way. Has anyone seen this type of symptom. The main board has three smd caps and the ESR measures them in circuit within specs based on their capacity and voltage. They also look ok and no leakage to be seen.
Any thoughts?
Simmi
So, after opening up the tv, I did a visual inspection of the power board, connectors etc. All looked ok. I have checked all the electrolytes with an ESR meter and checked their capacity out of circuit and they are fine.
When disconnecting CN801 between power board (BN44- 00268A) and the main logic board and then plugging in power, the back leds flash on/off twice and then stay on permanently.
Measuring voltages on CN801 is as follows NOTE (Missing pins are not connected):
AC PWR Plugged In
1 - PS = 0v
2 - Sync = 0v
3 - SB = 5.22v
5 - GND = 0v
7 - 18v = 0v
9 - GND = 0v
11 - GND = 0v
13 - 5.1v = 0v
15 - 5.1v = 0v
17 - GND = 0v
19- 13v = 0v
21 = 13v = 0v
23 - INV-ON = 0v
25 - E-PWM = 0v
27 - 5V-DET = 0v
29 - GND = 0v
30 - GND = 0v
AC PWR Plugged In with CN801 Disconnected and led lights on (Led light flashes twice on/off and then stays on permanently.)
1 - PS = 0.78v
2 - Sync = 0v
3 - SB = 5.22v
5 - GND = 0v
7 - 18v = 18v
9 - GND = 0v
11 - GND = 0v
13 - 5.1v = 5.22v
15 - 5.1v = 5.22v
17 - GND = 0v
19- 13v = 12.43v
21 = 13v = 12.43v
23 - INV-ON = 3.8v
25 - E-PWM = 4.95v
27 - 5V-DET = 5.21v
29 - GND = 0v
30 - GND = 0v
AC PWR Plugged In, all cables plugged and pwr on via remote
1 - PS = fluctuating 0.5 - 0.7v
2 - Sync = 0v
3 - SB = fluctuating 0.6 - 2.4v
5 - GND = 0v
7 - 18v = fluctuating 5 - 12v
9 - GND = 0v
11 - GND = 0v
13 - 5.1v = fluctuating 0.6 - 2.2v
15 - 5.1v = fluctuating 0.6 - 2.2v
17 - GND = 0v
19- 13v = fluctuating 1.90 - 5.80v
21 = 13v = fluctuating 1.90 - 5.80v
23 - INV-ON = fluctuating 0.1 - 1v
25 - E-PWM = fluctuating 0.2 - 2.3v
27 - 5V-DET = 0v
29 - GND = 0v
30 - GND = 0v
I've also tried disconnecting everything from the main board, except the CN801 pwr cable and it still causes the fluctuation of the voltages.
I'm thinking the power board is ok, but the main board may have a problem. It would appear it's loading one of the supplies off the power board and then retrying to power it up again in a cyclic way. Has anyone seen this type of symptom. The main board has three smd caps and the ESR measures them in circuit within specs based on their capacity and voltage. They also look ok and no leakage to be seen.
Any thoughts?
Simmi
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