no standby light appeared - samsung tv with psu board bn44-0060B

[ejxxx]

the tv still works if I dettached those connectors on the psu board and then reconnect it for about 2 days wherein the standby light will appear again and tv works normally but unfortunately after 2 days of using it ,standby light doesn't show again.This is actually a recurring problem.
However, i already replaced out of tolerance capacitors, checked resistors but i found something unusual when I diode checked(D904 ) with part no.SR204 Shottkey 2A 40V. My reading shows .000001v on both sides of the diode for in--circuit diode test. however,there's a resistance if I checked it and not shorted as well.As I removed and checked it i found the diode test fwd voltage to be 0.1596v. Can this be the problem? because in the datasheet it should be 0.5v.

If I substitute different shottkey diodes,still my reading shows .000001v on both sides of the diode. I don't know if the problem is in the OVP of slc1012c and I don't have schematics.

hope you can help me.

[freakaftr8]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

Regardless of what you're finding do you still have 5 V on your standby pin after the power light goes out?

[ejxxx]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

Regardless of what you're finding do you still have 5 V on your standby pin after the power light goes out?

none

[budm]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

Can we see high res pictures of the whole top side and bottom side of the board?
Also please verify the board number, bn44-0060B does not look right.
What is the TV model number?

[nomoresonys]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

Yep, some pics. and the full model number would be very helpful.

[ejxxx]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

Can we see high res pictures of the whole top side and bottom side of the board?
Also please verify the board number, bn44-0060B does not look right.
What is the TV model number?

bn44-00605B

[budm]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

OK, now I need to see the picture of the bottom side of the power supply board so I can trace out the circuit.
That D904 is in the LED backlighst power supply circuit and it may be connected in parallel with < 1 Ohm resistor that is why it shows conduction in both directions in the circuit.

[budm]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

If you run the power supply board by itself without having it connected to the main board, is the A5V staying at 5V?

[ejxxx]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

OK, now I need to see the picture of the bottom side of the power supply board so I can trace out the circuit.
That D904 is in the LED backlighst power supply circuit and it may be connected in parallel with < 1 Ohm resistor that is why it shows conduction in both directions in the circuit.

this diode is connected in parallel with two parallel resistor of 4.7ohms, so 4.7/2 will be 2.35, considering the fwd voltage of d904 is 0.5v and its rating is 40v ,2amp on datasheet .however its diode resistance(dr) is not linear, if
I will use 2amp then theoretically 0.5v/2 = 0.25 .If they will be connected together in parallel it will have an output total resistance < dr < 2.35

i have to figure it out again if I measured 200ohms on this connection.

[nomoresonys]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

"full model number of tv"

[budm]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

"I will use 2amp then theoretically 0.5v/2 = 0.25 .If they will be connected together in parallel it will have an output total resistance < dr < 2.35 " It does not work that way.
The VF spec is at full forward current your meter is not putting out th same current so the Vf will not be what is shown on the spec sheet. Parallel two equal Vf diodes in parallel will not make the total Vf in half, look up how diode functions then you will understand why.
As I indicate, that diode is in the backlights section, what you need to do is to work in the 5V STANDBY section. If you think that DIODE is bad then you can leave that Diode out and fix the standby power supply section.
Where is the pictures of the bottom side of the board as requested?

[ejxxx]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

yesterday before I put back the connectors on the psu , I measured D904 which is parallel to two parallel resistor of 4.7ohms(theoretically 4.7/2=2.35ohms but measured 2.6ohms) thereby,it will have a total resistance of 2.6ohms. So, total resistance <=2.6 <diode resistance. diode test fwd and reverse (in-circuit) is 0.0001v.
TV works again.. standby light appeared but my kids wanted to watch tv and there's nothing I can do to check further for sure it will be only good for 1 or 2 days...

[budm]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

Sounds like you may have bad solder joints, I would resolder all the component leg that are soldered to the through hole rivets, especially the transformer legs.

"diode test fwd and reverse (in-circuit) is 0.0001v." that is normal, the meter is showing you the Vdrops on the resistors.
When you check very low Ohm resistance you need to subtract your probe wires resistance from your reading, you should touch your meter probes together to see how much your meter probe wires have.

[ejxxx]

Re: no standby light appeared - samsung tv with psu board bn44-0060B

thanks sir budm.. so my mission is to resolder the transformer legs. check A5v, and the rest of cnm8 connector and also on the remote side .
i have to check temp of mainboard processor and also check if there is a capacitor or component connected between the mainboard and the a5v . check also the ovp of slc1012. check regulator of the boards.Take some pictures
and have a bottle of beer