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

[BmD_Online]

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

I'm answering myself :
T6.3AH250VP (really difficult to read).
I's time delay one (T...).

[BmD_Online]

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

Tried with right fuse, but same problem !
I have double checked all capacitors and RM801. All OK.
IC is correct too.

I have a doubt about connecting LCD inverter to CM802 or CM803. I haven't checked before deconnecting it !

[vinceroger69]

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

have you checked the bridge rectifier for shorts? also maybe build yourself a dim bulb tester as it will save you keep blowing fuses and show if a short is still present.
http://www.geek-tips.com/2015/11/22/dim-bulb-tester/

[BmD_Online]

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

You're right. ts4b05g shorts between each pins (kept soldered).
I don't know dim bulb tester. I will have a look.

My parents (it's not my TV) found a new Samsung for less than 180€. They bought it !
I will try to repair this one, but just for fun.
At some point, the repair is no longer going to be profitable !

I will try to change bridge rectifier.
Wait and see.

[vinceroger69]

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

remove the part and test out of circuit just in case your getting false readings

[BmD_Online]

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

Damn. Really hard to unscrew and unsolder !

[vinceroger69]

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

add some fresh solder too the joints makes removing it easier can you use a small pair of needle nosed pliers to loosen the screw? if not maybe remove that capacitor in front of it.

[budm]

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

What are the RESISTANCE reading between + and - , and between ~ and ~ of that bridge rectifier?
Did you also check the RESISTANCE between the S and D pin of the PFC MOSFET QP801S?
Samsung BN96-03057A (PSLF201501B) Power Supply.

[BmD_Online]

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

Hi,
between + and -, I read 1 ohm
between ~ and ~, I read 5.4 ohms

QP801S ? You're talking about F9222L ICM801S ?
I read different values according to my multimeter :
in diode mode : 480
in resistance mode, weirded values, changing during reading

[budm]

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

QP801S is a MOSFET for the PFC circuit, it is mounted on the same heatsing where PFC Diode DP802 is.
Pictures provided by shopjimmy:
Samsung BN96-03057A (PSLF201501B)

[BmD_Online]

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

Yes, got it : W20NM60 mosfet.
I read 0.6 ohm between S and D

[budm]

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

I would remove that retest it off the board before trying to remove the bridge rectifier.

[BmD_Online]

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

Phew, I've removed it !

Using my multimeter or using an electronic tester (mtester) I read different values.
See attached pictures.

Using multimeter, I read 0.7 Ohm.
Using mtester, I read different values around 10-15K, sometimes around 5K.

[budm]

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

https://www.badcaps.net/forum/attach...1&d=1579443332
That MOSFET is shorted, now recheck the resistance between + and - pins of the bridge again, also between ~ and ~ of the bridge again.

[BmD_Online]

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

Resistance is the same between + and -, and between ~and ~ : about 77K.
I will change the MOSFET !

[budm]

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

Resistance is the same between + and -, and between ~and ~ : about 77K.
I will change the MOSFET !

Good, the low Ohms reading you were getting before was due to shorted out PFC MOSFET.
You should replace the PFC Controller IC at the same time since more likely it is also damage when the MOSFET shorted out, it MAY cause the damage to the new MOSFET if you do not replace it.

[BmD_Online]

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

Which component is "PFC Controller IC" ?
Please don't tell me it's ICP801S (tda4863-2) ! SMD component, I hate them !

[budm]

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

Which component is "PFC Controller IC" ?
Please don't tell me it's ICP801S (tda4863-2) ! SMD component, I hate them !

Yep, it is.
https://cdn.badcaps-static.com/pdfs/...7e28445b8e.pdf

Also make sure RP819 is still good, it should be <1 Ohms + your meter probes resistance.

[BmD_Online]

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

Soldered, I read 0.8 Ohms.
Probing my meter itselt, I have about 0.6-0.7 Ohms.
I can't be more precise.

Edit : Soldered, not Unsoldered !

[budm]

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

That is fine.