Sony KDL 42W705 backlight no sound, no picture

[sansiro2]

Hi guys, got a Sony 42W705 LED TV. Only get backlight but no picture. I get a one second blast of sound when I switch the TV on but then silence. I have changed the T Con and the main logic board to no avail. If I pull the LDVS off or the power cable to the main board while TV is on nothing happens.

By the way for the T Con I matched the TX-5542T35C01 bit of the barcode, although the rest is slightly different.

Any ideas what could be the cause?

[budm]

Re: Sony KDL 42W705 backlight no sound, no picture

Pictures of the whole back side of the TV so we can see all the boards?

[sansiro2]

Re: Sony KDL 42W705 backlight no sound, no picture

1st pic Power board with cover taken off
2nd pic main board
3rd secondary av board which clips on to main board
The t con is underneath the secondary av board

[budm]

Re: Sony KDL 42W705 backlight no sound, no picture

I expect to see the FRC (Frame Rate Conversion) board between the main board and the T-CON board, it does not look like it has one.
Did you check the DCV on both ends of the SMD fuse with ref to the chassis to see if the T-CON is getting the 12VDC? It is not going to be easy due to the location of the T-CON board.

[dick_barton]

Re: Sony KDL 42W705 backlight no sound, no picture

Have you checked F101 on the Tcon. Recently received a Tcon where the fuse was blown.

[sansiro2]

Re: Sony KDL 42W705 backlight no sound, no picture

F101 appears to be fine. It's going to be awkward but where would I put the test probes to test if 12v is coming in? I assume tv needs to be switched on. Apologies been a since I done any electronics

[budm]

Re: Sony KDL 42W705 backlight no sound, no picture

Black probe on the chassis Gnd, red probe on the fuse's ends (check DCV at both ends), TV has to be ON.

[sansiro2]

Re: Sony KDL 42W705 backlight no sound, no picture

Thanks I'll try to find a way to do this given the awkward positioning and let you know. Thanks

[nanias]

Re: Sony KDL 42W705 backlight no sound, no picture

Can you tell us the result?

I have the same problem.

Any one can help with a solution for this sintomes?

Thanks

[nanias]

Re: Sony KDL 42W705 backlight no sound, no picture

Please, If someone can help I appreciate because Sony is make me crazy...

I have already change the cable (and nothing change so that was not the problem):
SONY KDL-42W705B LVDS CABLE 1-848-110-11

This are the Symptoms in na attached video:
https://drive.google.com/open?id=0B_...UtEZklmYUliZzA

Can it be T-Con?

Thank you
Antunes
Lisbon-Portugal

[ReeceyBurger123]

Re: Sony KDL 42W705 backlight no sound, no picture

Hi Nanias, what have you tested so far ? I also have the same set with a blown up Tcon I will diagnose it soon. Shame the guy NEVER BOTHERED to update the thread.

[nanias]

Re: Sony KDL 42W705 backlight no sound, no picture

In fact I dind't check nothing else because i am only a curious guy.

I read that could be a problem with the cable LVDS and I start there

Because the T-Com is more expensive i was trying by parts.

My afraid is that the problem can be the LCD panel. That's why I show the Symptoms to see if someone can help because i found a lot of people with the same problem.
Thks

[sansiro2]

Re: Sony KDL 42W705 backlight no sound, no picture

Sorry guys I didn't get an email notification. But diagnosis was short circuited panel so TV is a goner. Shame on Sony, used to a brand you could rely on.

[nanias]

Re: Sony KDL 42W705 backlight no sound, no picture

Thanks sansiro2.

I made some more tests. I unplug one of the cables of T-Com and the result was this in the photo. No image. I do the same on the other cable and the result was the same. No image in none of the sides.

Any help?

Thanks

[sansiro2]

Re: Sony KDL 42W705 backlight no sound, no picture

Sorry I have no idea. Maybe the technical guys can help.

[Moreno83]

Re: Sony KDL 42W705 backlight no sound, no picture

That looks like a bad t-con or bad panel! You need to measure the voltages as described above!

The T-con had a small fuse ( usually ) next to the LVDS port. Its very small and says something like "F101". Measure for continuity and measure the voltage.

[nanias]

Re: Sony KDL 42W705 backlight no sound, no picture

That looks like a bad t-con or bad panel! You need to measure the voltages as described above!

The T-con had a small fuse ( usually ) next to the LVDS port. Its very small and says something like "F101". Measure for continuity and measure the voltage.

Hi Moreno83,
Thank you so much. I will do that.

My doubt is exactly that: T-con or bad panel. How can I be shure? Because if it is the panel everyone said to forget this TV and buy a new one. I will buy a T-con if I have the certainiity that this is the problem. I must import the T-Con and it will cost me about 50€ (used).

Can you please tell me a test or a trick to eliminate this doubt? For exemple, if the fuse is ok can I assume that the problem is the panel?

Can someone confirm that I have understand correct the possition of the probe of the multimeter? (I attach a picture).

For someone who be interested i alsso attached a picture of the back of the TV.

Thank you so much for everyone who can help.

Nanias

[dick_barton]

Re: Sony KDL 42W705 backlight no sound, no picture

Screw your tcon board back down. Black lead on chassis. Red lead on one side of the fuse and read dc voltage, then red lead on other side of fuse and read dc voltage and the readings should be identical.

[nanias]

Re: Sony KDL 42W705 backlight no sound, no picture

...the readings should be identical.

If they are identical, can I assume the problem i have mencioned is on the LCD panel or that is nor conclusive and the problem can be at the T-Con but on other part (not the fuse).

Forgive me the questions but I will open the TV and I would like to be conclusive at that time to see everything when the tv is open. Furthermore english is not my language and sometimes I don't understand words (i use Google translation...).

Thanks again

[KEHT]

Re: Sony KDL 42W705 backlight no sound, no picture

Any ideas what could be the cause?

Yep, unscrew metal shields from the bottom of the LCD. Something like this.
http://www.imagebam.com/image/219837503058597

Check burned routes on the flexible cables. Something like this.
http://www.imagebam.com/image/913b54503058762

Congratulations, you got a s/c in your LCD. Yes, its time to buy a new TV