Sony KDL-40BX420 strange back light issue.

[Dang]

Now this one is proving a pain, basically the Tv will turn on and give a picture but after a short period of time it will switch off needing to be unplugged from the mains to restart it, this period of time can be almost instant or after 30 seconds, maybe a minute, maybe five minutes, can even be longer. I've just done a little testing and have a stable 25V to the inverter, indeed disconnecting this has proved to stabilise the Tv, you can see the menus and such like faintly appear until it auto-powers down to standby and then can happily be turned back on, so for sure there is an issue with the back light, somewhere?????

I've tested all the components on the inverter and they all seem to measure out fine, strangely removing this and replacing it has allowed the Tv to be stable for over 20 minutes now, would this point to an earthing issue?

[Dang]

Re: Sony KDL-40BX420 strange back light issue.

From reading on Ebay and looking at this video, it seems this particular Tv suffers from inverter issues.

https://www.youtube.com/watch?v=94WsUFb0vV0

Incidentally the Tv has been on for nearly an hour now, all good so far so I think I'm going to resolder a few joints and see how I get on.

[Dang]

Re: Sony KDL-40BX420 strange back light issue.

OK, so the inverter shield is back on, all components checked very closely with a magnifying glass for any dry joints and has now been working fine pretty much since this morning without issue. It's a strange one, I can only think it to be either an earthing issue or the possibility of a temporary short somewhere: maybe the pins used to connect the inverter to CCFL tube a little bent???? I don't know but for know it's working and all seems fine, I'll keep on using it and see if it rears it's ugly head again.

[budm]

Re: Sony KDL-40BX420 strange back light issue.

What happen if you turn down the backlights level (not the Brightness level)? Will it stay on longer?

[Dang]

Re: Sony KDL-40BX420 strange back light issue.

This is the thing, it seems perfectly fine now, it seems that just by removing it and replacing it has some how resolved the issue, I have no idea what it's done but it's been fine since this morning.

Any ideas what may of been the problem?

[budm]

Re: Sony KDL-40BX420 strange back light issue.

May be loose connections, bad board mounting screws so you were not getting good ground, etc.

[Harry Demers]

Re: Sony KDL-40BX420 strange back light issue.

Is your KDL 40BX420 still working ?
As I understand your post DISCONNECTING-RECONNECTING the backlight/inverter board resolved the problem(s) it was having, is that correct ?
If so, great... QUESTION : wouldn't unplugging the power cord, say over-night, have effectively done the same thing ??? Maybe not ... no telling how long inter-connected boards/components will effect each other. Grounding PCBs is another matter... the best-of things or the worst-of things, ie.- a "floating ground" for RF or IF, etc.

Is your unit a 2011 ? Looks like your T-Com board is 'built-into' the screen as mine w/ only a ribbon cable connecting it to the Main Board, which is totally different than my 2011 KDL 40BX420. I had to replace my P/S and Main after a strong power surge and now that ribbon cable started to burn on the left side at both ends. Any ideas on that ?
Appears as though the Display Panel has to be 'tore-down' to access/replace T-Con...
Saw one YouTube on this BUT for a totally different SONY w/ four ribbon cables, not the single ribbon cable we have. Ever taken apart your Display Panel ? If so...easy or not?