LG TV stopped working.

[budm]

Re: LG TV stopped working.

EAX64905501 power supply
TV LG 47LN575V totally dead

basically have voltage across the primary side but no voltage readings on secondary side,also legend voltages have no reading

done so far:
checked all diodes for shorts all ok
voltage reading across main cap 330 volts
no fuses blown

any ideas

thanks

330VDC is normal (your country AC is around 230VAC) when the TV is not turned on and the PS-ON is not present.
We need the DC V readings of all the connector on the power supply board that goes to the main board, make sure to put down pin name and follow by the Voltage reading when TV is off and when TV power switch is activated so we can easily see what you have and do not have for each pin without guessing what each pin is for.
Also pictures of the whole backside of the TV showing all the boards.

[sordids999]

Re: LG TV stopped working.

LEGEND P201

readings when tv is off and on

gnd gnd
12v= 0v 12v=0v
12v= 0v 12v=0v
gnd gnd
24v= 0v 24v=0v
gnd gnd
3.5v=0v PD/M2=0v
3.5v=0v PD/M1=0v
PW-ON=0v DRV-ON=0v

thanks

[budm]

Re: LG TV stopped working.

OK, so we need to at least get the STBY power supply running first.
What is the P/N as printed on top of the SMPS IC501 for the STBY power supply?
We need to get the spec sheet of the IC then find out what DC V we have on the pins of the IC.

[sordids999]

Re: LG TV stopped working.

From what I can read
3BR4765JR H1331Z2V IE329186C39
PIN1 -153.4 PIN2 -154.0 PIN3 -154.3 PIN4 0.00
PIN5 -154.0 PIN6 -154.0 PIN7 NO PIN PIN8 -152.

[budm]

Re: LG TV stopped working.

What did you use for GND ref. for your meter? It looks like you use the chassis GND. You are making measurement in the hot side of the circuit so the GND ref. for your meter will be the negative leg of the main filter cap in the hot side.

[sordids999]

Re: LG TV stopped working.

sorry my mistake now using negative leg of the main filter cap in the hot side

PIN1 0.00v
PIN2 0.00v
PIN3 0.00v
PIN4 0.00v
PIN5 0.00v
PIN6 0.00v
PIN7 NO PIN
PIN8 325v

[budm]

Re: LG TV stopped working.

ICE3BR4765J.
Check the resistance between VCC pin and GND pin.
Check the resistance between CS pin and GND pin

[sordids999]

Re: LG TV stopped working.

0.68 VCC to GND
0.00 CS to GND

[budm]

Re: LG TV stopped working.

0.68 Ohms?
If that is the case there is shorted parts on that VCC pin, it is either internal shorts or, filter caps connected to the VCC pin shorted, or Zener diode (if there is one) shorted.
You have to trace out and see what are connected to the VCC pin, you can remove the IC or remove the caps to see which one will make the shorts go away.

[Th3_uN1Qu3]

Re: LG TV stopped working.

Desolder the controller chip first, then continue measuring. If measurement on VCC is no longer 0.68 ohms, instead a value more around 10 Kohms or higher, then the controller chip is dead and you need to replace that. If you are still getting a short, then you need to test other components on the board.

[budm]

Re: LG TV stopped working.

MLCC C501 is connected between VCC and GND.

[Th3_uN1Qu3]

Re: LG TV stopped working.

Ceramic capacitors usually fail (almost) dead short. This smells to me like a semiconductor short, my money would still be on the controller chip being the culprit.

[tom66]

Re: LG TV stopped working.

I had a Vestel board a long time ago where the main microcontroller was dead short. It definitely happens.

[Th3_uN1Qu3]

Re: LG TV stopped working.

A large, low voltage MCU is one thing, a small, low powered power supply regulator which has a Vcc of 10s of volts is another. They have different failure modes. I should have been more specific.

[sordids999]

Re: LG TV stopped working.

Update **
Ordered ICE3BR4765J fitted voltages came back but also had the dreaded one blink backlight fault so ended up tracing it back to some faulty leds
In test mode now

Thanks for the help everyone

[budm]

Re: LG TV stopped working.

Thanks for the follow-up.