Any TV techs out there?

[JT]

I have a LG 3d plasma tv 50PZ570. it works fine from cold but if you turn it off, it won't switch back on.
My 1st thought was the power PCB but after some testing I disconnected the Z-SUS board (last in daisy chain) it turns on & off fine.
none of the caps are hot on any board. Any ideas?

[ltdslip]

Try http://www.austech.info/index.php might have to register

[Delft Maloo]

I have a LG 3d plasma tv 50PZ570. it works fine from cold but if you turn it off, it won't switch back on.
My 1st thought was the power PCB but after some testing I disconnected the Z-SUS board (last in daisy chain) it turns on & off fine.
none of the caps are hot on any board. Any ideas?

normally always the other way around,lol. Ill ask my tech's when i get into work in the morning, we saved an electronics repair business from closing its doors a few years ago but i don't do much of the stuff myself.

[JT]

normally always the other way around,lol. Ill ask my tech's when i get into work in the morning, we saved an electronics repair business from closing its doors a few years ago but i don't do much of the stuff myself.

Thanks mate.

[Delft Maloo]

I have a LG 3d plasma tv 50PZ570. it works fine from cold but if you turn it off, it won't switch back on.
My 1st thought was the power PCB but after some testing I disconnected the Z-SUS board (last in daisy chain) it turns on & off fine.
none of the caps are hot on any board. Any ideas?

how are you disconnecting the z sus board? from at the z sus board itself or from the feed from the power supply?

[JT]

how are you disconnecting the z sus board? from at the z sus board itself or from the feed from the power supply?

4714
I disconnected the cable from the circled plug at top of z sus board

[JT]

https://www.dropbox.com/s/680laqlb9s8898b/lg_50pz570t-zb_50pz570w-zb_chassis_pd12b%20%281%29.pdf?dl=0

[amckiwi]

https://www.dropbox.com/s/680laqlb9s8898b/lg_50pz570t-zb_50pz570w-zb_chassis_pd12b%20%281%29.pdf?dl=0

Need to create an account to go any further here

[Delft Maloo]

He said it is possible for the Z sus to be the issue but its not that common, normal culprit is Y sus board, he can't remember the exact configuration of that model but some of the other LG tv's have the Z sus being fed after the Y sus board, confirm without actually testing it.

if the problem was occurring from cold start and fine once running for awhile it would usually be the capacitors on the power supply board not charging enough on start up, they can appear fine sometimes on the outside but still not hold enough current.

[Delft Maloo]

https://www.dropbox.com/s/680laqlb9s8898b/lg_50pz570t-zb_50pz570w-zb_chassis_pd12b%20%281%29.pdf?dl=0

sorry didn't check the thread before i left work today, would have passed this onto him.

[JT]

Need to create an account to go any further here

no you don't. just click on "no thanks" at the bottom of the popup

[JT]

yes the configuration is power --> Y SUS --> Z SUS

[JT]

didn't get a chance to have another play around with this on the weekend. Will have another look at the voltages in the next day or so.

[duke5700]

Heat could be an impedance/ohms things.. As it gets warm, it expands, dry solder joint gets worse. Really a guess without looking at it. I chased a fault in a gate PCB.. everything tested well in situ. Only by hapenstance I wiggled a resistor.. dry solder joint.

I would pull the caps on the PSU. Its only a few bucks to try it out, especially if you are good with an iron.

[Micks]

Yes fluctuations in power can cook those caps, seen this many times before!

[JT]

Thanks guys. will have a good look for dry joints on all the boards.

[Micks]

If that doesn't work Joe put it on the rubbish heap & buy yourself a decent set! :lol:

[JT]

If that doesn't work Joe put it on the rubbish heap & buy yourself a decent set! :lol:

The picture is awesome on this unit. Sh!ts all over any other el cheapo set available now so I would like to keep it if I can get it going for little outlay.

[JT]

4736
couldn't see any dry joints visually or by tugging components. However at the top left the board looks discoloured under 4 resistors

[Delft Maloo]

if you have a soldering iron just remelt all the solder points, you will only see the cracks from the back of the board and sometimes they are very difficult to see regardless. They usually look like a little ring in the solder, try not to spend to long on the solder points otherwise you will lift a track, quickest way to do this is to melt some solder on the tip of the iron before you touch the board, that way the wet solder on the iron transfers the heat straight away and your not left holding the iron excessively long on the board for too long.

Regards the resistors if you have a multimeter you should be able find the values on the internet, the coloured rings will give you this, then measure them up against what they are supposed to be.
Also go over all the caps, make sure they have been left to discharge for at least a few minutes after being plugged in before touching them, you can sometimes see if they are buggered just by a visual inspection as they tend to bulge out, sometimes it can be as simple as the top being slightly raised/domed up.

Don't really have access to my Tech at the moment as I'm in the USA holidaying with my family and he's the one id need to speak too to bounce more in depth stuff off.

[JT]

Thanks DM. I will break out the soldering iron & give it a go.

[JT]

well it isn't the z-sus board (like I suspected). got one delivered today off ebay, installed it & problem not fixed. Back to square one

[JT]

Fixed!! there were some dodgy solder joints on the main power board.

[whitels1ss]

Well done JT....

Good on you for working it out, so many people give up on fixing anything these days! :soap:

[JT]

Well done JT....

Good on you for working it out, so many people give up on fixing anything these days! :soap:

Yeah thanks. absolutely stoked.