55EC930V Help please

[jram]

Ok, I have downloaded the SMPS guide.

The symptoms are that the LG symbol lights and flickers when the black power button on the back of the unit is pressed and also when the remote power button is pressed. The TV does not power on.

AC (240V) is present ath the sck100? where the power arrives on the main board. All fuses are intact and all apart from the one by the main socket have 120V.

Power Supply Board Low Voltage Test 1 yields the following:

3.5V at pins 3 and 5 of P201.

I disconnected P2300 ribbon cable and added R110 across pins 1&3 or 1&5 but this yields no click and no 12v or 24v power when AC is supplied.

So either the relay is bad or ??? Any guidance greatly appreciated

[nomoresonys]

Re: 55EC930V Help please

How bout some good pictures of all the boards and one of the whole back including all the boards, and a up close picture of the P2300 and any legend/map of the expected voltages.

[R_J]

Re: 55EC930V Help please

Have you checked all the fuses in the secondary? F501 should be good, its for the standby circuit.
It looks like optocoupler IC503 drives Q501 to drive the relay so see if you have any voltage on the cold side of the optocoupler. To check the voltage on the output side of the opto you need to use the HOT ground, BD103 (-) or one of the main caps (-) lead

You can also check if you have voltage across C507, this is the supply voltage for the relay
[quoye]I disconnected P2300 ribbon cable and added R110 across pins 1&3 or 1&5 [/quote] What is R110? you need to use a 1KΩ resistor to jump between 3.5V (J100) and PWR-ON (J94)

[jram]

Re: 55EC930V Help please

Ok, Thanks for the feedback guys,

@nomoresonys - I'll attach the photos below.

@R_J - The fuses are all good. On checking the voltage to the Opto with the link across pins 1&3, I see a fluctuating voltage of 1V +- 0.1v which is not good (I expected 3.55V - correct?).

With the link removed, I see a steady 3.55V at the terminals on IC503 (on the low side)

[nomoresonys]

Re: 55EC930V Help please

Recheck P201, do it just like #3 in my signature below.

[jram]

Re: 55EC930V Help please

@nomoresonys Thank you, I will. Unfortunately have to go away for some days due to family illness - will catch up next week. Thanks for your help

[nomoresonys]

Re: 55EC930V Help please

Glad to help, best wishes, hope they have a speedy recovery.

[jram]

Re: 55EC930V Help please

OK - I'm back! Many thanks for your good wishes

I made sure everything was plugged in but inverted the power board to gain access to P201 pins from the rear. I attach a picture of the pins and the legend above

The voltages are as follows:

System power on but in standby

0 0
0 0
0 0
0 0
0 0
0 0
3.55 3.55
0 3.55
1.9mV 0

I then pressed the remote power button once. The LG led dimmed and recovered.

the following (same) voltages were measured

0 0
0 0
0 0
0 0
0 0
0 0
3.55 3.55
0 3.55
1.9mV 0

[R_J]

Re: 55EC930V Help please

Did you meaure the voltages WHILE pushing the power button, or just push the power button, and after the led dimmed/recovered, measured the voltages again?
Check the PWR-ON pin while pressing the power button

[jram]

Re: 55EC930V Help please

Did you meaure the voltages WHILE pushing the power button, or just push the power button, and after the led dimmed/recovered, measured the voltages again?
Check the PWR-ON pin while pressing the power button

Thanks for your patience - sorry

OK with the PWR button held ON

0 0
0-5mV 2-40mV*
0-35mV* 2-40mV*
0 0
0-5mV* 1-5mV*
0 0
3.55V 3.55V
0 3.55V
1.9 - 50mV 0-?? Volts - oscillates high enough to get the meter to switch scales and then cuts off to zero and restarts - period about 2 seconds

*These values oscillate up and down with a period of about 2-3 seconds

Thank you.

[Diah]

Re: 55EC930V Help please

OK - I'm back! Many thanks for your good wishes

I made sure everything was plugged in but inverted the power board to gain access to P201 pins from the rear.

this is wrong work. your MB and T-CON driver boards should disconnected from PSU when you like to trace the 12 & 24 Volts on PSU.

Never..NEVER connect the both mentioned board to PSU if you are dont have clear stable 12 & 24 V on PSU.

yours photo https://www.badcaps.net/forum/attach...2&d=1566988083 solder out the both driver IC near to LB501 502 0n the back side of PSU. you will find the issue there if one of them cracked out.

[jram]

Re: 55EC930V Help please

this is wrong work. your MB and T-CON driver boards should disconnected from PSU when you like to trace the 12 & 24 Volts on PSU.

Never..NEVER connect the both mentioned board to PSU if you are dont have clear stable 12 & 24 V on PSU.

This is the recommended technique from @nomoresonys.

For your technique, please may I ask you to answer with details of your technique, test points used and any other information available?

Many thanks

[nomoresonys]

Re: 55EC930V Help please

Ideally you leave the board screwed down and use skinny probes or back-probes to measure the voltages, I use stripped down bread ties on occasion.

[jram]

Re: 55EC930V Help please

@nomoresonys, my results at #10. Had to flip the board over but can't see it would make much difference since it was still connected to the other boards per the instructions.

Seems there is a problem getting the 12 and 24V to start/hold on

[Diah]

Re: 55EC930V Help please

This is the recommended technique from @nomoresonys.

For your technique, please may I ask you to answer with details of your technique, test points used and any other information available?

Many thanks

there are no specific technique required.. all roads drive you to ROM.. only notice the following:
you have downloaded SMPS guide as u mentioned at your first post.
point one as i mentioned keep the MB and T-CON driver board out,, disconnected from PSU. solder pin 3 which are stand by voltage to pin power ON this will make the relay click look like MB connected and send command signal to power on the PSU. with this state trace the 12 and 24 volts..

check the 2 driver ic which i wrote at my pervious post. i found many LG OLED one of these driver cracked out.

[jram]

Re: 55EC930V Help please

Thank you - I'll get to it

[jram]

Re: 55EC930V Help please

With pin 3 connected to to pin 1, the pin 3 voltage oscillates at about 1-2Hz between 1-2.6 V. There is no click, there is no 12V or 24V measurable. Pretty much the same results as my 1st post.

Anyone got a circuit diagram?

Thanks

[Diah]

Re: 55EC930V Help please

With pin 3 connected to to pin 1, the pin 3 voltage oscillates at about 1-2Hz between 1-2.6 V. There is no click, there is no 12V or 24V measurable. Pretty much the same results as my 1st post.

Anyone got a circuit diagram?

Thanks

i think you had wrong contact.
you should connect 3.5V to the pin PWR_on not DRV_on

PWR_ON = power on ( Supplying 12 24 V to MB ) Relay Click .... this one we like to trace first.
DRV_ON = driver on ( supplying 24 volts to T-CON driver this will work only if you have relay click and 12 24 V present by step (PWR_ON )

[R_J]

Re: 55EC930V Help please

check if you have voltage across C507, this is the supply voltage for the relay and is also the feed back voltage for the standby circuit

If you are working from the top of the board, use J50 (hot ground) and and check the voltage on D505 cathode.
The relay needs to operate before you will get 12v or 24v The standby voltage should not drop when you short pin 1&3

I suspect you have a bad cap in the standby circuit, C503,C507,C504

In the original post you say you measure 120v at the fuses, is that measured to chassis ground or from hot ground?
To measure the voltage on F101 and F102 you need to have your meter on DCV and the ground needs to be on C621 negative or use the negative of BD101

[Diah]

Re: 55EC930V Help please

120 V on Fuses as he report are very low.
you can disconnect one side only of Fuses F101 and F102 to remove the load to check the relay will click or not..
you can also take out the relay and open the cover case and check it of function out side the board