Samsung UE40F6400AY relay sound and reboots continuosly

[R_J]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

QS851 is the switch for the B5V. It is turned on when there is B13V present. This voltage is not needed in standby

[Luis8]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

QS851 is the switch for the B5V. It is turned on when there is B13V present. This voltage is not needed in standby

You are right, i am learning along the process
As you previously said QS861 is turned on and off by PCS802S photocoupler and this is managed by the high voltage section. Now i understand why you said me to replace CS804 earlier...

I tested the double diode DS811 and it is ok, i tested the zener ZDS802 too and it works fine.
On CS804 i have 22.8v when the PSU starts, when the relay is turned off it drops to 18-19v, i have the same voltage on the collector of QS801.
On emitter and the base of QS801 i have variable voltages and i don't understand.

I feel a bit lost right now can you give me a little push?

[R_J]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

I did NOT say QS861 is controlled by PCS802S. It's gate is controlled by PS_ON/OFF. When the main board is NOT CONNECTED, RS863 and RS862 supplies +5V to turn on the gate of QS861 When this happens, the Drain is effectively connected to the source (ground).

With just the power supply on the bench, does the relay still click on/off? if it does, short CNM803 pin20 (PS_ON/OFF) to ground. this will place the power supply into standby and the relay should stop clicking.

QS861 does turn on PCS802S as well which turns on QS801 which supplies VCC_AUX (16V) to icp801s (PFC) and icm801cs which are turned off in standby. The Relay could be turned OFF by the PRT Enable line as well

[Davi.p]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

Hi Luis, this tv serie has got a tipical fault in backlight controlling ic or ic's.

[R_J]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

After re-reading the thread,

I made some other measurement and testing and i was wrong, with the mainboard disconnected from the PSU the led lights are blinking because of the relay shutting of the power. When i am lucky and the TV starts correctly it seems that the backlight strips are all good.

You could have a led problem, if one of the strips is bad/intermittent It could be turning the power supply off via the PRT Enable line.

[Luis8]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

With just the power supply on the bench, does the relay still click on/off? if it does, short CNM803 pin20 (PS_ON/OFF) to ground. this will place the power supply into standby and the relay should stop clicking.

Yes with just the power supply on the bench the relay still clicking. As you told if i short PS_ON to ground the relay stops to click but as soon as release the short it start to click again.

QS861 does turn on PCS802S as well which turns on QS801 which supplies VCC_AUX (16V) to icp801s (PFC) and icm801cs which are turned off in standby. The Relay could be turned OFF by the PRT Enable line as well

I start to suppose that protection enable signal is my case but i see that is managed by QQ853 and so on... What approach can i apply to be more faster and to don't check component by component?

Hi Luis, this tv serie has got a tipical fault in backlight controlling ic or ic's.

After re-reading the thread, You could have a led problem, if one of the strips is bad/intermittent It could be turning the power supply off via the PRT Enable line.

Do you have any suggestion on how i can check before the led driver IC's if i have a broken led strip without opening the TV frame? In theory i think that i should block PRT Enable signal but in pratice how can i do that?

I am sorry for dumb questions but i do that just as hobby with the goal to learn a bit of electronics.
Thanks to everyone that will try to help me out

[Davi.p]

Re: Samsung UE40F6400AY relay sound and reboots continuosly

Without that i read everything, if the the BL type is not local dimming, there's a very very simple BL tester, made with a graetz bridge and a resistor, you can test if all strips lights up and then order the possible faulty chip and then change it.