Sony Bravia KDL-46NX800 46” TV; Intermittant Display

[SonyinNC]

Hello, I'm looking for some assistance on repairing my Sony Bravia KDL-46NX800 46” TV, it is about 5 or 6 years old and is intermittent. At times it will display solid vertical bars & lines in the display with no video content. The sound plays through the speakers and there is no video content displayed, except for the solid vertical bars. You can also select other video sources with no change. I can turn the TV off for a few hours and return, sometimes the TV will work and sometime it will not. As soon as I start to look into fixing the problem, it starts working again.

Here is what I know so fare:

1) During cold power up from “stand-by” the TV will power up and will display solid vertical bars & lines in the display with no video content. Audio has no issues. (See attached pictures)

2) Switching video sources has not effect.

3) Switching to “stand-by” and back to “on” has no effect, solid vertical bars & lines return.

4) Switch to “off” and back on via side power switch has no effect.

5) The solid vertical bars & lines will slowly change width and colors.

6) After a period of time, (sometimes 1 to 10 minutes, sometimes 20-45 minutes) the display will return to normal and show correct video content.

7) I was able to download a Sony Service Manual for this TV, see attached.

8) The service manual provides good information on Self Diags, disassembly, set up and basic schematic diagram. But no theory of operation or troubleshooting information is provided.

9) With display solid vertical bars & lines in the display, the “Self Test” does not report any errors on the “STANDBY” LED. STANDY LED remains solid green when in standby and off in operate.

10) With TV operating normally with normal video content, I can enter the “Self Check” mode using the remote. The displayed Self Check diagnostic screen will display zero errors.

11) With TV operating normally, I can turn it off and back on and display is normal.

12) With TV operating normally, I can turn it off, wait for 15-30 minutes; the display will go back to displaying solid vertical bars & lines. After a 10-15 minute warm up time the display will return to normal.

Any information on this issue will be much appreciated. I am planning to remove the back cover and check for loose connections and reseat connectors in hopes of finding something or clearing up this intermittent issue.

Thanks, Tom

[CapLeaker]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

disconnect one ribbon cable at a time from the T-con to the panel.
You also can look with an oscilloscope at the LVDS signal while turning on and off the menu all the time.
Maybe trying heat (hair dryer) or cold (can of air upside down) on the tcon / main board.

[SonyinNC]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

CapLeaker,

Thanks for the response. I have been keeping an eye on this TV for most of the day. After powering on this morning, having the display issue, then the video issue cleared up after about 45 minutes. While watching the TV for most of the day the issue has not returned. The issue seems to return after the TV has been off for 30 minutes or more.

I'm going to need to remove the back and get my hands into it. I'll keep you posted with what I find out.

Are there some resources that could provide me some theory of operation on these flat screen TVs? I would be interested in understanding how the work.

Thanks, Tom

[ReeceyBurger123]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Looks like a tab bond issue to me, take it apart and get some images buddy

[ryanfan03]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Maybe this could be a t-con issue? Maybe the AS-15 chip? I have a tv with similar problems that I am trying to fix with that chip replacement.

[SonyinNC]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

ReeceyBurger123,

I just got the back off while it is still on the stand. With limited experience on flat screen TV's I'm trying to learn the acronyms that is used for these TVs.

What does "tab bond issue" mean?

Thanks, Tom

[ReeceyBurger123]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Check this out:

https://m.youtube.com/watch?v=purk_SyiT44

[ReeceyBurger123]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Maybe this could be a t-con issue? Maybe the AS-15 chip? I have a tv with similar problems that I am trying to fix with that chip replacement.

I doubt this is a Tcon fault but not ruling it out, but deffo not an AS15 fault as the Lcd will still load but will have distorted image like green haze or full white etc AS15 wont cause lines and panel distortions like this.

[SonyinNC]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

ReeceyBurger123,

Interesting youtube video. The issue that TV is having is not quite like the issue that I have. It doeve video content, mine doesn't. The vertcal lines are dynamic or sporadic, my is more constant or constant, the lines and bars do not jump around. They do drift some and change size and colors. This happens in very slow motion and it will slowly spread across the full screen. But again, there is no video content in the image on the screen.

Thanks, Tom

[ReeceyBurger123]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Still could be a tab bond failure lots of goofy things go on when they do go. But do what Capleaker suggested first.

[SonyinNC]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Roger that,

1) "disconnect one ribbon cable at a time from the T-con to the panel". I'll need to remove the stand and lay the TV down to get to the ribbon cables on the bottom of the T-con module.

2) "You also can look with an oscilloscope at the LVDS signal while turning on and off the menu all the time". I do not have a oscilloscope handy, but could chase one down next week. I am not sure where to clip the probe to monitor this "LVDS" signal.

3) "Maybe trying heat (hair dryer) or cold (can of air upside down) on the tcon / main board'. This I can do, will have to try this later after the TV has been turned off for a while.

Thanks, Tom

[ReeceyBurger123]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

Yeah I think leaving the OS scope out would be a good idea if you dont know much. But other methods will help you let us know what happens

[SonyinNC]

Re: Sony Bravia KDL-46NX800 46” TV; Intermittant Display

This morning I turned on the TV and sure enough the solid vertical bars & lines were displayed. After about 30 minutes the display corrected itself. The problem is now consistently failing when 1st tuned on while cold. And it is consistently correcting itself after about 30-40 minutes.

The T-Con board is mounted near the bottom of the Sony TV. So I removed the TV from the base and laid it down on the kitchen table. I then remove the support bracket so I could remove the 4ea ribbon cables that are connected to the T-Con board. I removed the screws and then the T-Con board. Looked it over and could not visually find anything wrong with it. I noted the part numbers on the board and then reinstalled the T-Con board onto the TV. Connected the cables and then installed the TV on its stand.

Turned on the TV from a cold start, and wow, it came up with a good picture and no issues. Maybe, just maybe reseating the 4ea ribbon cables on the T-Con board corrected this intermittent issue. Will monitor for a while to see if this corrects the “intermittent solid vertical bars & lines” on the display.