42" 3D LED KALED423DXZA (not turning on)

[Hman545]

So i got a Kogan 42" tv for free a while ago that does not turn on and im trying to repair it for myself but had no luck so far.

- Once its plugged in, the red standby led comes on for about 2 seconds then turns green with out me pressing any buttons. The tv remains off.

- All caps look new on the supply board, no bulging or leaks. I changed a few of them with Rubycon's anyway, no difference.

- After leaving the tv unplugged for a few days it did turn on and remained on for hours until i turned it off which then it refused to turn back on.

- I've tried draining all the caps with a resistor but still nothing.

- Tried unplugging the soft power button on the side but still get the green led.

Anyone have any idea what it could be?
Any help would be appreciated.

Thanks.

edit: when it did turn on both video and audio worked perfectly.

[newtothis]

Re: 42" 3D LED KALED423DXZA (not turning on)

Pictures of your boards and overall layout please

Also close up of the connector between the Mainboard and PSU so we can see the writing next to it (PSU Side)

[Hman545]

Re: 42" 3D LED KALED423DXZA (not turning on)

[Hman545]

Re: 42" 3D LED KALED423DXZA (not turning on)

As soon as its plugged in theres 24v going to the backlight and 12v to the main board.
I think the issue is with the main board.

[Hman545]

Re: 42" 3D LED KALED423DXZA (not turning on)

.

[CapLeaker]

Re: 42" 3D LED KALED423DXZA (not turning on)

I don't think it is a PSU fault either.
5V Stby is generated on the PSU all the time and goes to the main board. Once you hit the power button on the TV, the main board returns that voltage to the PSU and thus telling it to turn all rails of the PSU on. So. Since the TV still behaves strangely and with all that you did, I say too there is something not right with the Main board.

As a piece of mind you can "force" the PSU on without the main board using two 1k resistors, each coming from 5V STBY to PSon and BLon. Backlight should be on and all the voltage rails should be on too.

[ausheaven]

Re: 42" 3D LED KALED423DXZA (not turning on)

Interesting I have a LED KALED463D1A with the same problem. Mine happened after a voltage surge due to lightning. Didn't turn on the first time but left it for a few days. Out of curiosity I turn it on and it works and had worked since. About 6 months later there was another lightning surge and it went off again, but no matter what I did and waited it wouldn't turned on. Meanwhile was trying to sort out the repairs and insurance. Turned it on after 6 weeks and it came back to life. Must be something to do with the PSU. It is just 2 years old. Your power supply is identical to the LED KALED423DXZA. Any one with suggestion.

[thoma]

Re: 42" 3D LED KALED423DXZA (not turning on)

Is there any schematic available?
regards thoma!

[ausheaven]

Re: 42" 3D LED KALED423DXZA (not turning on)

Unfortunately Unable to identify original maker. This is an OEM branded TV

[budm]

Re: 42" 3D LED KALED423DXZA (not turning on)

There are labels for the pins of the connectors on the power supply board and the main board, so how about giving us the DCV reading of each pin with the pin names next to the readings so we can see what are missing. You may have firmware/EEPROM problem.
They sure sells lots of models but no supports.
https://www.kogan.com/au/shop/for/led-tv/

[Hman545]

Re: 42" 3D LED KALED423DXZA (not turning on)

been unplugged for a couple weeks, no longer turns on.

on/off - 2.3v
A GND - 0v
A GND - 0v
BRT_OUT - 2.3v
BKLT_EN - 0.099v
12V - 12.25v
12V - 12.25v

Led light turns green after 2 seconds of powering on, does not respond to any buttons.

[budm]

Re: 42" 3D LED KALED423DXZA (not turning on)

"BKLT_EN - 0.099v" Main board is not sending the Backlights on signal.

[ReeceyBurger123]

Re: 42" 3D LED KALED423DXZA (not turning on)

As this is umc chassis with some sort of t.msd main board I would probably say the main board is at fault with corrupt firmware.