Samsung BN44-00808D power supply board troubleshooting

[Per Eriksson]

Hi,
I was given a samsung 65" lcd tv which is "dead" after a lightning strike.

Power supply board is a BN44-00808D , also have the marking L65S6N_FSM
Main board is a BN94-10803V

I've made some simple test.

With main board connected nothing happens when plugged in, no blinking lights or sounds.
Also kept it plugged in for a while and checked on the boards with a thermal camera, no hot spots detected.

With the main board disconnected the backlights turn on and stay on.

Checked the voltages in the connector going to the main board and they come out as follows,

Main board disconnected
pin name voltage
1 FAIL_COUNT 1,1
2 ANA_DIM 3,3
3 A13V 12,8
4 OD_On/Off 3,6
5 A13V 12,8
6 BLU_PWM 3,0
7 A13V 12,8
8 Power_On/Off 4,45
9 A13V 12,8
10 GND 0
11 GND 0
12 GND 0

Main board connected
pin name voltage
1 FAIL_COUNT 1,4
2 ANA_DIM 0
3 A13V 9,5
4 OD_On/Off 0
5 A13V 9,5
6 BLU_PWM 0
7 A13V 9,5
8 Power_On/Off 0
9 A13V 9,5
10 GND 0
11 GND 0
12 GND 0



As you can see the A13 voltage drops some which I find strange, if there was a short somewhere on the mainboard I think it would go to zero and/or a hotspot would be detected since the power board should be able to supply 4,7A.
I have no information about how the other voltages should behave unfortunately.
Thoughts on next step?

[dick_barton]

Re: Samsung BN44-00808D power supply board troubleshooting

There looks like a number of buck-boost voltage converters on the mainboard and any one of those may have gone faulty.
If you disconnect the power supply from the mainboard,
1) what resistance is there between the 12V line and ground on the power supply
2) and then on the mainboard 12V input to ground?

[neilc6]

Re: Samsung BN44-00808D power supply board troubleshooting

Voltages look ok and your main board is suspect. The A13V is supplying standby voltage which gets boosted to 13V with a pwr-on signal from the main board or when you disconnect it due to a pullup resistor for testing.

[jevlar]

Re: Samsung BN44-00808D power supply board troubleshooting

Voltages look ok and your main board is suspect. The A13V is supplying standby voltage which gets boosted to 13V with a pwr-on signal from the main board or when you disconnect it due to a pullup resistor for testing.

I'm also leaning towards that, read in another thread that the standby voltage could be around 8-9 volts so that would make sense

I talked to the folks I got the tv from and they told me everything connected to their adsl router had died so most likely the surge came into the tv via the ethernet port on the mainboard and killed it.

So I'm hunting a new mainboard and with that comes a new question.
I'm not finding a BN94-10803 V board but I do find some A , D, W and so on.

Do anyone have any insight in how much differs?
I don't care about the tuner part of it, if it has ethernet and hdmi I'm all good.

[neilc6]

Re: Samsung BN44-00808D power supply board troubleshooting

Naming convention typically has the the letter suffix as the revision and as long as the part number is the same, they should be compatible (fit, form and function). However, I have seen the occasional board/model completely different with a different revision letter (someone didn't follow the standards and gave it a new revision instead of new part number). I would just make sure all the connectors are the same.