Sony Bravia KDL-42EX440 - problem - turns off after switching on

[Diah]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

my way to do any edge LED back light by replace them all
1- with hot air gun from the down side of the strips heat them and took all out
2- with shave plate scratch the LED strips more from right side and left side
3 place solder on the old place and the new scratch with iron
4- replace the new LED in place with finger press it at its place then with iron i heat the solder outside the LED, it will mild all solder of one side and the led i can feel it pressed down a little. same way to opposite side.

[Diah]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

can you post photo of yours LED Back light socket on PSU .. ?

you said each strip had 56 LED, this huge if they are not separated as groups. to be sure if they are 6 or 3 volts

[zarko]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

Yes it is 56 LEDs in series per strip (one group).
I tried LEDs with 3V at fIrst but I could not get them to shine.
After that I tested LEDs with 6V, all LEDs are shining except 5 LEDs which are bad.
I expected one LED to be bad. How come 5 LEDs were open connection?

On PSU there are two connectors for LED back-light. Two pins per connector.
Photos attached.

[Diah]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

Yes it is 56 LEDs in series per strip (one group).
I tried LEDs with 3V at fIrst but I could not get them to shine.
After that I tested LEDs with 6V, all LEDs are shining except 5 LEDs which are bad.
I expected one LED to be bad. How come 5 LEDs were open connection?

On PSU there are two connectors for LED back-light. Two pins per connector.
Photos attached.

what are the label reading of the 2 caps near back light socket on PSU ?

[zarko]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

Both caps are 10uF, 450V.

[zarko]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

I have analysed those 4020 LEDs that are working fine.

This is what I measured:
Voltage applied:___| 5.5V | 5.75V | 6.00V | 6.2V
Measured current:_| 20mA | 40mA | 60mA | 80mA
Measured current is nor exactly the same for all LEDs, this is average value.

I am thinking of switching to 2835 LEDs.
I have found this LED in a local store but I am not sure if it would be suitable for LCD TV usage.
https://store.comet.rs/Catalogue/Product/48222/

[Diah]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

you are going with this thinking to damage the strips and it may cause damage your PSU. stay on original 4020

[diif]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

I am thinking of switching to 2835 LEDs.
I have found this LED in a local store but I am not sure if it would be suitable for LCD TV usage.
https://store.comet.rs/Catalogue/Product/48222/

I wouldn't change the LED dimensions on an edge lit TV. The LEDs were chosen for a reason. They reflect their light down the inside of the acrylic sheet on edge lit TVs. Changing the LED width will upset those reflections.

[zarko]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

Thank you Diah & diif.
I will stay with 4020.
I guess it is Aliexpress then.

[Elviscocho]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

I’m sorry for my bad English because is not my first language, but I want to know if you resolved the problem. I have the same issue on the same tv model and I want to be sure if it’s the led strips that are bad so I can order a new one and replace it.

[zarko]

Re: Sony Bravia KDL-42EX440 - problem - turns off after switching on

Hello Elviscocho,
Yes, I resolved the issue. Problem was in the led strips.