Sony Bravia kdl-42w705b sound and backlight but no picture

[SlyAKs]

As above..  Haven't yet bought this set, but this is what the fault is according to the owner.. The backlight is visible and there is sound, just a black screen. T-con/main fault?

Seán

[astracat]

hi and merry xmas to all who reads this
done one of these with o/c fuse on tcon may be your problem
good luck
astracat

[SlyAKs]

Cheers astracat, will be the 1st thing I check.. Hopefully a nice easy fix! 😀

[SlyAKs]

So just tested t-con fuse and all is fine, DCV between chassis GND and both sides of the fuse is 12v... Any ideas folks?

[downunder]

Hi Sean,

Strange there are no error codes. Faulty T-con would give code 5, backlights would give code 6. If it has AV Out terminals you could connect it to a monitor. If you get picture, it would rule out the Main unless the Main or try the old 'bright light against the screen' trick to see if there is data on the screen.

Bruce

[SlyAKs]

Hi Bruce, cheers for the reply!
No error codes at all mate, set powers on with no problems. There is a backlight, but screen remains blank..
I tried connecting the TV to another using a scart lead, would that work? When I done that the other set received a signal, but the screen remained blank also..

[downunder]

So the screen on the second set remained blank just like your faulty Sony. On the strength of that I'd say it's almost certain to be a faulty main bd.

Bruce

[SlyAKs]

Good stuff, I managed to pick up a main bd online yesterday for very little, so hopefully that'll do the job.. Cheers from the help!
Sean

[SlyAKs]

Right, just connected this TV up to another set again via the av out and low and behold there is a picture.. I made the mistake of not connecting up an input last time, so obviously I wasn't gonna see anything....

So t-con or panel?

Any way of testing the t-con further? It's getting 12v and the smd fuse is fine. I have another t-con ordered, but I wouldn't mind trying to repair this one if possible

[SlyAKs]

Think I've found a shorted diode on the t-con, correct me if I'm wrong.. In diode mode on DMM I'm getting a reading of 0v in both directions.. Resistance in both directions is 0.7 ohms also. Can't find a schematic anywhere, but I'll keep digging.. See what else I can find here!

[downunder]

Hi Sly,

Sorry if I gave you a bum steer, but at least it virtually rules out the main board. If you locate a schematic for the T-Con, you should race out and buy a lottery ticket. Seems they don't exist, being classed as an integral part of the panel, which Sony themselves do not manufacture. From the T-Con image, it looks like they've gone for a blue ribbon (not) AUO panel.

BTW is this set a newer Smart LED TV, with all the innards fitted into the lower section of the cabinet? Have met a couple (55") that are actually powered by an external AC adaptor....quaint, but I was unable to track down a service manual for this one.

You'd best lift one end of that diode and test it out of circuit, in case it's across some low ohm component, but it looks promising. Be interesting to compare it to the replacement when it arrives. Check those smd series regulators (I see 2 of them) for correct output. Might also be enlightening to disconnect alternately the two flexies that go to the screen and see if anything appears on the screen, in case the panel is pulling things down.

Bon chance- Bruce

[SlyAKs]

Again, cheers for your input Bruce, much appreciated!

Yeah this is one of the newer smart led sets with everything crammed in at the bottom and an external AC adapter...

Haven't had a chance to look at the t-con in much detail since my last post, though today the main bd that I ordered arrived.
Bunged it in straight away and powered it up to get 5 red blinks (t-con fault?). Strange that the original main didn't throw this error code? I then unplugged the t-con and the set seemed to power on with backlights, then powered off with 8 red blinks of the led... Any ideas?
 Still waiting for the new t-con to arrive, hopefully that'll sort it

Sean

[downunder]

Well, the plot thickens. According to service manuals for similar built models, code 8 is "a software error (also main board's memory or CAM
module is suspect) - BAXL board error". BAXL board is the main board. If it's the one I'm picturing, the tuner board piggy backs on the left of the main (looking from the rsend). Can't recall the error code on the one's I did, but both were storm damaged and both main and tuner boards were fried, and they weren't cheap (new). Thank goodness for insurance. Code 5 is a T-Con error, but with the T-Con unplugged it might throw up a different code.
Hopefully, the replacement T-Con will sort it. I'd just wait and see.

Bruce

[pipone]

Hi there,

i'm on same boat. There is a backlight, but screen remains blank. When power on just hear sound from tuner about 1 sec and then stops.
No any red error codes from diode, except powered it up without (disconnected TCON cable) to get 5 red blinks.
Already tested T-CON and getting 12v both sides of the fuse. So same situation - Main BAXL board or TCON? Any ideas?

SlyAKs, can i ask you did you change T-CON and fix the problem finally?

 Thanks in advance