Soniq S55V16A-AU stuck in standby

[samsonn]

I've got a 55" Soniq LED TV which is stuck in standby mode (initiator LED on, but no picture/sound/backlight). It will intermittently start working again for a few days or weeks, but it has been months since the last time it turned on. I've seen a lot of similar issues with Soniq TVs that were fixed by updating the firmware, but I need to turn it on to update the firmware so no luck there.

I've taken the back off and visually inspected it but everything looks fine. No exploded capacitors or signs of overheating etc. All of the 1117 regulators on the main board were outputting 3.3v so don't think they're the issue.

The voltages a the main board power connector were:

PSON 3.3V
5VS 5.2V
5V 5.2V
12V 0V
BLON 0V
ADJ 1.55V
OPC 0V

Most of them look normal I guess? Feel like the 12V rail should be 12V but the PSU might just be waiting for a signal from the main board to turn in on. Don't really know the best way to verify one way or another.

Not sure what my next steps should be, any advice is greatly appreciated.

[dick_barton]

Re: Soniq S55V16A-AU stuck in standby

There are 13 wires in connector CON 2.
Could you list them for example as below :-

No.  Label  Reading
Pin 1 +5V   4.8V
Pin 2 GND   0V
Pin 3 GND   0V
Pin 4 BL   2.5V

What dc voltage do you have between the two legs of the large capacitor

[budm]

Re: Soniq S55V16A-AU stuck in standby

1) Please provide the result in the format as requested by dick_barton.
2) PS-ON (3.3V as reported) for turning on the rest of the power supply is present so the switched 12V should be present but it is not.
3) BL-ON is reported as 0V so that is missing also.
4) I need good clear straight shots of the whole bottom side of the power supply board.
5) I need the closed up of the power supply connector so I can see pins' label.
6) I need the pictures of the whole backside of the TV showing all the boards so I can see how all the boards are connected together.

[samsonn]

Re: Soniq S55V16A-AU stuck in standby

The voltage across the large capacitor was 382V.


Here is the pinout and voltages of the mainboard connector.

Pin 1   PSON  3.3V
Pin 2   5VS   5.2V
Pin 3   5V   5.2V
Pin 4   5V   5.2V
Pin 5   5V   5.2V
Pin 6   GND   0V
Pin 7   12V   0V
Pin 8   12V   0V
Pin 9   BL_ON  0V
Pin 10  GND   0V
Pin 11  ADJ   1.55V
Pin 12  OPC   0V  (Not connected to anything?)
Pin 13  GND   0V
Pin 14  GND   0V
Pin 15  GND   0V
Pin 16  GND   0V

And the pinout at the other end on the PSU (CON2)

Pin 1   12V
Pin 2   12V
Pin 3   SGND  (Connected to GND on the main board)
Pin 4   SGND 
Pin 5   SGND 
Pin 6   5V
Pin 7   5V  
Pin 8   5VSB   (Connected to 5VS on the main board)
Pin 9   PS/ON  
Pin 10  BK/ON  (Connected to BL_ON on the main board)
Pin 11  ADJ  
Pin 12  SGND 
Pin 13  SGND

I've attached the requested photos, let me know if they're clear enough. I can pull out my good camera and have another go tomorrow if necessary.

Cheers

[dick_barton]

Re: Soniq S55V16A-AU stuck in standby

Is the 3.3V at PSON present with the mainboard disconnected from the power supply and nothing connected to it? I believe some power supplies need PSON taken low to bring up the other supplies.

[samsonn]

Re: Soniq S55V16A-AU stuck in standby

Nope, without the mainboard connected the only voltages are 5VSB at 5.2V and ADJ at around 0.75V. Everything else is 0V.

[nomoresonys]

Re: Soniq S55V16A-AU stuck in standby

Try with tv UNPLUGGED from main power, unhook cable from powerboard to mainboard, leave it off, on powerboard, use about a 1k resistor to jump 5v SB pin to PS/ON pin and another resistor from BK/ON pin to 5v SB, plug power into powerboard, see if you have the expected voltages and see if the backlights come on and stay on.

[budm]

Re: Soniq S55V16A-AU stuck in standby

1) So PD-ON is present, 3.3V as reported and the PFC boosted Voltage is also present, 382V as reported.
2) But the 12V and LED power supply, generated by transformer T2, is not working so you need to check the resistor and the capacitor (check capacitance) that I marked.
3) I also need the P/N of the IC that I marked so we can see if the VCC is present to run the IC or not.
4) I also need better focused pictures of the whole top side of the power supply board because I cannot read the designators of the resistor and the cap.

Power supply board PCB: MAGMEET MP420D-QG3

[samsonn]

Re: Soniq S55V16A-AU stuck in standby

Hey so I've found what the problem was. The transistor below the capacitor budm marked in his images had been knocked and the pcb pad on one of it legs had been ripped up a little bit. See the attached image. I soldered a wire from the leg to a nearby pad and the tv came back to life.

Feel kinda silly I didn't notice it earlier, could've saved everyone some time. Thanks everyone for you help.

Cheers

[dick_barton]

Re: Soniq S55V16A-AU stuck in standby

Another one saved from the scapheap.

[budm]

Re: Soniq S55V16A-AU stuck in standby

Hey so I've found what the problem was. The transistor below the capacitor budm marked in his images had been knocked and the pcb pad on one of it legs had been ripped up a little bit. See the attached image. I soldered a wire from the leg to a nearby pad and the tv came back to life.

Feel kinda silly I didn't notice it earlier, could've saved everyone some time. Thanks everyone for you help.

Cheers

I cannot tell from picture as to which Transistor that is.
So did someone work on this board before you?
I am glad you are able to see it and fix the problem.