Samsung LNS3251DA won’t power on, no sound, no standby light-power board problems

[R_J]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

I believe TS4K60-A should be the same

[nomoresonys]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Ok, bridge rectifier should be the first or close to it, to check when fuses keep popping.

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Lift one end of RM801 then recheck the resistance of the bridge again.
What is the exact resistance reading between ~ and ~?

RM801 ? sure ?
when lifted :
5.2 Ohms between + and -
0.7 Ohms between ~ and ~ (internal multimeter resistance is about 0.6 0.7 too).

[budm]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

To get 0.7 Ohms between ~ pins, at least two internal diodes of the bridge have to be dead shorts.
Did you remove the bridge and test it yet?

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Finally, I have unsoldered bridge rectifier.
And... all diodes are blown.
about 6 Ohms between + and -
about 1 Ohm between ~ and ~
In diode mode, all pins beeps between each other.

I have ordered another brider rectifier (same ref) from AliExpress.
Chinese new year, dispatch time... I should receive it within 37 days !

In the meantime, I have received new MOSFET. I have compared values and confirm previous one isn't blown.

[BmD_Online]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Hi again.
I've received my bridge rectifier and replaced it.

I have also ordered another power board (used).
With this replacement board, the TV works. So I can compare components between the two board if needed.

I've replaced the bridge rectifier on my board and re-soldered the MOSFET.

Now, fuse isn't blowing. Great !
But, TV stay in standby mode. I can't power it on.
Red led is blinking... pressing power button does nothing.

[nomoresonys]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Maybe compare voltages between the good board and the bad one, from the bridge right on thru, checking the mosfets and diodes and resistors and whatever else is checkable.

[nomoresonys]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Maybe check those readings first with the mainboard unhooked from powerboard, not likely since it hasn't yet but you wouldn't want a faulty powerboard to damage the mainboard, of course a lot of the tests are done with no power to the boards.

[nomoresonys]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

Did you check all the caps right by the bridge?

[nomoresonys]

Re: Samsung LNS3251DA won't power on, no sound, no standby light-power board problem

A good rule is ALWAYS check new components you get from anywhere before installing, if possible, can save a lot of troubleshooting if you catch any bad ones before installing.