Sony KDL-22BX200 no picture, backlight ok

[yoghi07]

Hi guys I'm giving a try at repairing a sony bravia lcd tv, which doesn't work.
When you plug it in, the backlight flashes briefly and stays on, but no picture shows up.
The led indicator should turn orange and then green when you press the power button, but instead it stays red.
Another issue is that you hear a buzzing noise coming from the back of the tv.

I opened it up and it seems like someone has already replaced the transformer inverter and MAYBE the main transformer (I'm not sure about that) on the psu.

What could the problem be? I'm thinking that the power could not be reaching the main board (I tried connecting a usb device and it gets no power).
But then again, the led indicator light comes on..so yeah I have no clue.

What do you guys think I should check on the board? Today I will take some pictures of the boards.

Thank you so much!!

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

I took some photos of the mb and the psu, for reference!

I was wondering if buying a new mb would help, I could currently get one for 30€...

Thanks for the help!

Edit: I also found out that a fuse on the psu (4th picture top right corner) has been short-circuited with copper wire. It was definitely opened before!

[newtothis]

Re: Sony KDL-22BX200 no picture, backlight ok

Have a multimeter?

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

Sadly, just an analog one. What voltages should I check in your opinion?

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

I also noticed that the optocoupler on the psu (white, 5th picture upper left corner) is a bit brownish. I tested the impedence on the diode side and it's the same if I measure both ways!
Could it be that? Just this optocoupler failing? I will get a new one this week, will update.

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

I'm starting to think that the psu is the real issue here. I also checked every fuse on the mainboard and they're all ok!

[budm]

Re: Sony KDL-22BX200 no picture, backlight ok

You need to find out if you are getting either 5V or 12VDC on the smd fuse on the T-CON board.

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

Checked, fuse is ok.

[vinceroger69]

Re: Sony KDL-22BX200 no picture, backlight ok

Have you checked you have voltage to both sides of the t con board fuse what does it read?

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

Yes, 5V both sides.

[yoghi07]

Re: Sony KDL-22BX200 no picture, backlight ok

I can't find a replacement for the psu at a decent price! Damn!