Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

[more_smarter]

Hello everyone, my first thread here. Been lurking a lot and trying to re-learn some electronics repair during unemployment.

I've picked up a TV for free to try and fix for a friend whose set died. It's a Sony KDL-46XBR4. The issue is this:

The TV powers on and the backlight and speakers all function normally (you can hear static or a source if plugged in). It takes a good while before any picture is actually displayed (I was told after it "warms up from 30min to several hours). I brought it home and sure enough it eventually shows picture but I wasn't going to sit around long enough to find out so I came back a few hours later and it was working and looks great.

Powering off the TV and back on immediately "resets" the issue and it takes the obscene amount of time to start showing a picture again (the backlight functions fine). I powered it up into the self-check and came back when eventually it displayed it showing no problems.

The back panel is off and I don't see any issues visually. From what I've probed so far, the power supply seems to be supplying the correct voltages. I have yet to take off any of the circuit boards to look at the backs so that's the next step. I'm suspecting a possible leaky capacitor issue.

I've searched for this issue quite a bit but have yet to see any posts/videos about this specific issue (backlight and sound on, but no display until suddenly POOF it's fine). Maybe my googling is weak, or there is in fact no info on this issue, so any help and direction would be much appreciated! I do not have an oscilloscope (yet) so just some basic soldering tools and a Fluke multimeter.

Thanks very much!

[Diah]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

The TV powers on and the backlight and speakers all function normally (you can hear static or a source if plugged in). It takes a good while before any picture is actually displayed (I was told after it "warms up from 30min to several hours).

The back panel is off and I don't see any issues visually. From what I've probed so far, the power supply seems to be supplying the correct voltages. I have yet to take off any of the circuit boards to look at the backs so that's the next step. I'm suspecting a possible leaky capacitor issue.

I've searched for this issue quite a bit but have yet to see any posts/videos about this specific issue (backlight and sound on, but no display until suddenly POOF it's fine). Maybe my googling is weak, or there is in fact no info on this issue, so any help and direction would be much appreciated! I do not have an oscilloscope (yet) so just some basic soldering tools and a Fluke multimeter.

Thanks very much!

you dont need oscilloscope at this issue...
yours suspecting are correct, hearing static or sound after feeding source its caps on the power boards ..
also post clear focused photo for yours power boards specially near the socket which it goes to main boards ( the cold area )

[more_smarter]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

you dont need oscilloscope at this issue...
yours suspecting are correct, hearing static or sound after feeding source its caps on the power boards ..
also post clear focused photo for yours power boards specially near the socket which it goes to main boards ( the cold area )

Here are some hi-res photos, hopefully you can see what you need.

The hiss is a very low level from the speakers when volume is above 0. I can hear the sound completely shut off when going to 0 volume.

The TV has been on about an hour when taking these photos. The T-Con board and all the ICs behind the plates feel warm to the touch, but no video signal yet, just backlight and sound.

[Diah]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

1- you need to clean the dust you have at all boards from both sides and make visual inspect to soldering joint .
2- reduce load and power on the set to check if it show picture at power on ( reduce load .. such unplug speaker...... disconnect ribbon cable one side at time between T-CON and panel )
3-on power boards all caps on the 12V line need to test the ESR of them out side the circuit. any suspect need to replace.

[more_smarter]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Thanks Diah! I'll be pulling it apart more to give it a good clean and inspection and will try your steps and report back in a few days!

[more_smarter]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

An update:

I've checked all the caps on the power boards and they seem to be close to what the rating says and I see no signs of failure. Reinstalled the caps and tested the TV and it powers on like before with only the backlight and no video signal.

I removed the T-Con board and the one directly connected to it underneath the heatsink assemblies so I could play with the ribbon cables. Unplugging either center ribbon cable results in that half of the display going full white. It doesn't seem to be a cable connection issue.

I left the TV on and after 1.5-2 hours the picture signal fired up as it has been doing. I tried disconnecting the ribbon cables from the t-con and could notice an audible change from the t-con board when unplugging it. It coincides with the picture signal starting as I tried powering the TV off and on and could hear the buzz start a few seconds after the backlight comes on when the video signal starts up.

I also didn't have to wait several hours after power cycling the TV to get video signal this time. Perhaps it's because I have the large heatsink assembly removed and the board is running warmer? I cycled it a good dozen times while listening to the buzz that starts when I get picture displaying and I've narrowed it down to the colored areas in the attached photo. Unplugging the matching ribbon cable definitely stops the sound.

I'm leaving the TV now to cool and see if the picture will immediately display or if it will have to 'warm up' the 1+ hour it normally does.

[Diah]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

please repeat the test of ribbon when the set start from cold condition ..as following

1- feed the set with signal that you be sure can hear the sound
2- disconnect the whole side at once mean ( ribbon 1 & 2 at once and ribbon 3 & 4 at once )

when you got half screen white at the test above did you see any picture sign on the other half ??

please post photo on whole back of the set showing how boards connected to each other.

Important notice. Never disconnect any ribbon or any other cable when the set ON.

[more_smarter]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

please repeat the test of ribbon when the set start from cold condition ..as following

1- feed the set with signal that you be sure can hear the sound
2- disconnect the whole side at once mean ( ribbon 1 & 2 at once and ribbon 3 & 4 at once )

when you got half screen white at the test above did you see any picture sign on the other half ??

please post photo on whole back of the set showing how boards connected to each other.

Important notice. Never disconnect any ribbon or any other cable when the set ON.

Hi Diah, figured I'd offer an update. I had to clear out some room in the basement due to a burst pipe so sadly this project came to a quick end resulting in recycling. Good news is recently was able to get a similar model TV that was working for free so my friend now has a working set for the time being.

Don't know if mods lock threads but that's it for this one.

[samolo75]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Hi,
Sorry for explaining a problem with a different TV here. The similarity is that after starting the TV it works ok for a few seconds and then starts showing ghost image with horizontal lines intermittently (except the very top). The frequency of the ghosting is steady, like every second or so, it goes from normal to ghosting every second and back.
The TV is a 49XE8096. I already did quite a lot of trouble shooting. And I got the doubt if the problem is in the panel or de Tcon.
When disconnecting one side from the panel at a time. The right side works fine, but the left will only show a white screen.
- No shorted capacitors.
- The ghosting seems to go at the same pace as the VGH ODD and VGH EVEN changes
- ODD/EVEN change from -7.05 to 28V
- VST seems to be steady to -7
This is the troubleshooting I did:
- In the left panel board (the one with the flex cables) I remove the resistors connecting ODD/EVEN. All the screen was flickering with horizontal lines and some vertical bands. The I solder a jumper between ODD-EVEN-VON (28V) on the panel side (ODD/EVEN are disconnected from the TCON as the resistors were removed)... then the image is really good but there is a black line on the top (where the image was always ok at the beginning).
- With the previous situation, I also remove the resistor from the left panel board connecting a signal called VST (-7V). Then all the screen (except the top part) has horizontal lines (no ghosting), very obvious lines. Then I disconnected ODD/EVEN from VON (28V) and connected it to VDD (15V). Then the horizontal lines became thinner and much lighter, noticeable but not much. And the black line on top also became thinner but still black.
I know it looks like something is wrong with the panel. But my question is if someone thinks that there is still the chance that the TCON board could make this king of fault. I read many people with a similar failure (the starting point) but for them the ghosting was steady and not blinking like mine. I wonder is something can be wrong with the level shifter. I could not find the schematic for the Tcon Board, or the data sheet from the RT6937 that seems to be the reference voltage generator.
Thanks in advance... any help is appreciated.

[nomoresonys]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Can you post a picture of the ghosting and lines of the display?

[nomoresonys]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Actually samolo75, you should start your own thread, this one is for fixing THIS tv, otherwise things just get too confusing. Read thru some stickies at the top of this category and don't forget to post good clear straight on pictures.

[samolo75]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Actually samolo75, you should start your own thread, this one is for fixing THIS tv, otherwise things just get too confusing. Read thru some stickies at the top of this category and don't forget to post good clear straight on pictures.

Hi,
Thanks for your answer. I would be happy to start a new thread, but I am new and I cannot open new threads, I hopped it was still ok to post it here, it was the most similar thread I found after all the search. Here they are the pictures of the screen. I got a new artifact and it happened after I tried to reflow the RT6937, they are the vertical bands on the right of the picture, they were not initially there. This is a learning experience for me, so I would be happy to keep working on it and at least understand what is wrong.
Thanks in advance

[nomoresonys]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Post some good straight on detailed pictures of each board and one of the whole back to see how they are all connected and maybe a closeup of RT6937.

[nomoresonys]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Go into settings and see if you can turn the backlight NOT brightness down to very little, see if the display clears up or changes any.

[samolo75]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Go into settings and see if you can turn the backlight NOT brightness down to very little, see if the display clears up or changes any.

Hi,
Thanks for your help. I went into settings and there was not option of lowering the backlight. The option was to enable the light sensor and the eco mode to HIGH. I made the room dark so the back light would go low... the image remained with the same artifacts.
I noticed something on the RT6937 IC, I think it has a crack. You can see it in the picture. Initially I thought it was a hair stocked to it, but it was not. You can see it on the left side of the picture (the scratch on the right I made it myself trying to remove it, looks like it is glued because I am sure I got it hot enough). Could this IC cause all this problems? I notice the crack after I tried to reflow the IC the first time, so it could be that I heated it too fast and it cracked, but I don't thing I was so rough.
Thanks!

[samolo75]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Sorry, I forgot to attach two of the picture. Here they are

[samolo75]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

Hi... sorry for the mess I created. I was able to start a new thread as the TV model and the fault are not really matching here.
The new thread for my TV https://www.badcaps.net/forum/showth...06#post1021306
If the admin can and wants to move this messages to the new thread I would be happy about it. Thanks

[nomoresonys]

Re: Sony KDL-46XBR4 - Backlight and Sound OK, no picture until on for ~30+ minutes

.