Samsung KM24WS

[BeginnerLVL1]

Hello,
my samsung monitor wont turn on, only blue led lights up.
The PSU board BN44-00195A gives only Power on voltage and stby 5V, all other rails are dead. I measured resistors and fusses, it is good, i try changing C802, but it still didnt work.
Thanks for any help

[1supertech]

Re: Samsung KM24WS

Pictures of the other side will be helpful

[BeginnerLVL1]

Re: Samsung KM24WS

Pictures of the other side will be helpful

OK, i take more photos.

I read lot about this problem, but nothing works for me.
Is a good idea to remove the glue?

Regards.

[BeginnerLVL1]

Re: Samsung KM24WS

Pictures of the other side will be helpful

Why is only 320 volts after rectifying instead of 400V?
Thanks.

[BeginnerLVL1]

Re: Samsung KM24WS

I replaced the BIG 400V cap and rectifier, 400V is now OK, but something went wrong and monitor still not works + standby woltage is dead too .

[budm]

Re: Samsung KM24WS

I replaced the BIG 400V cap and rectifier, 400V is now OK, but something went wrong and monitor still not works + standby woltage is dead too :(.

So you are saying that you are getting the 400VDC between the two legs of the main filter cap now? If that is the case then the STANSBY power supply has to be working because the VCC for the PFC Controller IC is running from the VCC generated by the AUX winding of the STANBY power transformer, something is not making sense here.

[budm]

Re: Samsung KM24WS

BTW, you MUST remove all those glue and inspect to see if any of the parts are damaged by the glues or not.
Those glues are corrosive and conductive when they turn brown like that.

[BeginnerLVL1]

Re: Samsung KM24WS

So you are saying that you are getting the 400VDC between the two legs of the main filter cap now? If that is the case then the STANSBY power supply has to be working because the VCC for the PFC Controller IC is running from the VCC generated by the AUX winding of the STANBY power transformer, something is not making sense here.

Hello,
actually I have no idea, why the standby PSU gone. Maybe it was killed by desoldering these parts in red frame. I desoldered capacitor and transistors for measure and then soldered it back, maybe i overheated them during soldering.
The transformer in green is for standby PSU.

Yes, i getting cca 400VDC on main filter cap.


Thanks for helping me

[budm]

Re: Samsung KM24WS

Are you sure you do not have STBY Voltage?
Check the DCV between the two legs of the cap I have marked.

[BeginnerLVL1]

Re: Samsung KM24WS

Are you sure you do not have STBY Voltage?
Check the DCV between the two legs of the cap I have marked.

Standby does not work at all

[budm]

Re: Samsung KM24WS

So 0 VDC between the two legs of the cap I have marked in POST #9, you do have 400VDC on the main filter cap so the standby power supply has to be working otherwise you will not have 400VDC on the main filter cap.
You need to check the diode that I have marked in the picture. I hope you are making the correct measurement.

[BeginnerLVL1]

Re: Samsung KM24WS

So 0 VDC between the two legs of the cap I have marked in POST #9, you do have 400VDC on the main filter cap so the standby power supply has to be working otherwise you will not have 400VDC on the main filter cap.
You need to check the diode that I have marked in the picture. I hope you are making the correct measurement.

Diode is OK, i made new measurement and on the main cap is only 320V, i must made mistake before...