Sony KDL-40XBR2 intermittent black screen?

[kgavionics]

Hi guys
I have a Sony KDL-40XBR2 and it's got a weird problem.I fixed a lot of tv,,but it's the first time i face a problem like this.I didn't trouble shoot this tv yet.i want just to know if someone have this problem, so i can fix it quickly.
the problem some times the the tv doesn't turn on,it has the green light in front and i hear the relay click, they the tv restarts and stays like that with a black screen and green light on.
to fix the problem, i have to disconnect the tv for few hours ( from 2 to 4 hours minium), then when i plug it back in.it works without any problems.
i noticed that if the tv shows black screen and i disconnect it from the power then plug it back in, the tv power up automatically, normally i have to press on the power button, but when the tv is working properly if unplug it and plug it back in,the tv stays off till i turn it on either with the remote or the power button.
i have downloaded the service manual and i don't see a similar problem.so before i take it apart i wanted to know if someone had this problem with this kind of tv.

thanks in advance

[Andrew F. Ali]

Re: Sony KDL-40XBR2 intermittent black screen?

Could you share the Service Manual with us so we could advise better?.....Off the top of my head, I would guess and I say guess, cold solder joints on BGA chip and/or faulty PSU.

[dskall]

Re: Sony KDL-40XBR2 intermittent black screen?

Backlights?

[kgavionics]

Re: Sony KDL-40XBR2 intermittent black screen?

Sorry guys i can't upload the manual, because its size exceeds 19 Mo.

[kgavionics]

Re: Sony KDL-40XBR2 intermittent black screen?

hi
i just took the tv apart.I checked the voltages they seems alright expect that the stby voltage is zero.
i think that it might be the problem.

[dskall]

Re: Sony KDL-40XBR2 intermittent black screen?

You would have to have standby voltage or you would have no panel light. You would not have your other voltages.

[Moreno83]

Re: Sony KDL-40XBR2 intermittent black screen?

I would look for cold solder joints on the PS.

[kgavionics]

Re: Sony KDL-40XBR2 intermittent black screen?

You would have to have standby voltage or you would have no panel light. You would not have your other voltages.

thanks for the heads up.
you're right dskall, i made a mistake i have the stby power (5V).
I have uploaded the schematic for the power supply.I have made the annotations in blue of the voltages that i measured when the tv is not working ( black screen).

i'm going to check if there's a bad solder join in the power supply.

[budm]

Re: Sony KDL-40XBR2 intermittent black screen?

Post #8
"I have uploaded the schematic for the power supply.I have made the annotations in blue of the voltages that i measured when the tv is not working ( black screen)."

So 18V is not present when TV stops working but the 7V and 11V are still present?
7V, 11V, 18V are generated by the same power transformer so if 7V and 11V are still present then you need to check the connection in that 18V section,

[kgavionics]

Re: Sony KDL-40XBR2 intermittent black screen?

guys i have updated the power supply manual with all the voltages.

[dskall]

Re: Sony KDL-40XBR2 intermittent black screen?

No 11v on CN6203. Bad connection. And you checked D6258?

[kgavionics]

Re: Sony KDL-40XBR2 intermittent black screen?

Thank you guys
i think i have fixed the problem.I checked for bad solder joint, but all seemed good,so i cleaned the bottom side of the PS with alcohol. I left it for 15 min then plug it back in.Now the tv seems to work without any problem. I've unplugged an plugged it it several times and it works.i'll keep trying just to confirm that the problem has been fixed 100%.

[dskall]

Re: Sony KDL-40XBR2 intermittent black screen?

I think you must have some cracked traces

[budm]

Re: Sony KDL-40XBR2 intermittent black screen?

No 7V and no 18 BUT 11V is present per updated PDF then I would resolder all those sections of the power supply.