Lg 50pn6500 Shuts off after 5 -20mins

[Gadjet]

Currently this set will turn on run anywhere from 5 to 20 mins. then turn off all on it's own. Doesn't have sleep mode on checked that. I left it plugged in one day after it shut off and it turned back on about 5 hrs later by itself. Don't see any bad caps or anything.

[selldoor]

Re: Lg 50pn6500 Shuts off after 5 -20mins

Sounds heat related - try having it on with the back off and a deskfan blowing on it to see if it stays on any longer.. Or after it has gone off try the fan and see if it comes back on.

[stj]

Re: Lg 50pn6500 Shuts off after 5 -20mins

i had this on a tv,
it was a voltage regulator breaking down as it got hot.

how i found it, i turned the tv on and metered all the regulators.
then i waited for it to die - in my case it was about 5min's so easier than yours.

then i metered all the regulators again.

[Gadjet]

Re: Lg 50pn6500 Shuts off after 5 -20mins

Turned it on this morning almost made it 30 mins. I believe it's heat related as well, after I took the back off I noticed 2 areas that look a bit dark I included the photos. I'll see if I can't hunt down the voltage regulator. STJ so you just replaced the regulator and it was fine?

[vinceroger69]

Re: Lg 50pn6500 Shuts off after 5 -20mins

the only think i can think of is to check for dry solder joints on the psu (expand when warm contract when cold) also maybe get a can of freeze spray and spray the regulators when the set goes off and see which one when cools allows it to turn straight back on but try the voltage checks first save buying freeze spray.

[selldoor]

Re: Lg 50pn6500 Shuts off after 5 -20mins

good brush down to get rid of the dust might help.
VRs are on the Green Board Probably U***

[stj]

Re: Lg 50pn6500 Shuts off after 5 -20mins

regulators are on the green board, i see atleast 4

in my case it was an 8pin regulator and i couldnt ID the damned chip.
it was generating 5v so i replaced it with a small pcb with a different regulator on it!
http://www.dx.com/p/mini-3a-4-5-28v-...r-green-238815

i dont recommend this unless you really cant fix it properly though!

[Gadjet]

Re: Lg 50pn6500 Shuts off after 5 -20mins

Which green board the buffer board with the ic chips?

[vinceroger69]

Re: Lg 50pn6500 Shuts off after 5 -20mins

i would guess the main board the one in pic one on the right.

[junker_unit]

Re: Lg 50pn6500 Shuts off after 5 -20mins

To anyone reading this who can't find a replacement main board, it might be possible to fix this problem without buying anything. I borrowed a trick from computer repair forums - it involves removing the problem circuit board and baking it in the oven to reflow the solder joints. Yes, that's right.

If the TV works fine for a little while but then suddenly powers off, it is most likely a heat problem. If the TV warms up and cools down many times over months or years, it can cause fractures in the solder joints that produce exactly this kind of problem. It works fine when cool, but after warming up the fractures expand and it fails again.

I fixed my LG TV by removing the main board and baking it in the oven at 375 for about 7 minutes. Put it on a baking sheet suspended on a few crumpled up balls of aluminum foil. Let it cool completely before placing it back in the TV. Don't go any longer than 7-8 minutes because you don't want to melt any of the plastic connectors. After 7 minutes there were no signs of melting or warping on my main board, so you should be safe at that temperature/time. Most solder melts at 360-370 degrees so a temp of 375 is necessary.

[dskall]

Re: Lg 50pn6500 Shuts off after 5 -20mins

This is not reflow as the temps do not get high enough to melt lead free solder with melting temps above 400F. I suspect flux is the key to the temporary success. You are reaching temps high enough to activate the flux and clean the oxides which act as an insulator and reestablish contact. Reballing is more of a long term fix if done properly.

[junker_unit]

Re: Lg 50pn6500 Shuts off after 5 -20mins

This is not reflow as the temps do not get high enough to melt lead free solder with melting temps above 400F. I suspect flux is the key to the temporary success. You are reaching temps high enough to activate the flux and clean the oxides which act as an insulator and reestablish contact. Reballing is more of a long term fix if done properly.

Good to know. I did the same "fix" with a 2008 laptop video card and it's been going strong a few years now without needing to redo it again. I assume it uses similar lead free solder. Just a suggestion for anyone wanting to breathe a few more years of life into their old TVs.

[aseke]

Re: Lg 50pn6500 Shuts off after 5 -20mins

To anyone reading this who can't find a replacement main board, it might be possible to fix this problem without buying anything. I borrowed a trick from computer repair forums - it involves removing the problem circuit board and baking it in the oven to reflow the solder joints. Yes, that's right.

If the TV works fine for a little while but then suddenly powers off, it is most likely a heat problem. If the TV warms up and cools down many times over months or years, it can cause fractures in the solder joints that produce exactly this kind of problem. It works fine when cool, but after warming up the fractures expand and it fails again.

I fixed my LG TV by removing the main board and baking it in the oven at 375 for about 7 minutes. Put it on a baking sheet suspended on a few crumpled up balls of aluminum foil. Let it cool completely before placing it back in the TV. Don't go any longer than 7-8 minutes because you don't want to melt any of the plastic connectors. After 7 minutes there were no signs of melting or warping on my main board, so you should be safe at that temperature/time. Most solder melts at 360-370 degrees so a temp of 375 is necessary.

When you say 7 minutes in the oven do you mean when the oven is cold or when the oven is pre heated?

[Nick's Tvs]

Re: Lg 50pn6500 Shuts off after 5 -20mins

I highly recommend you do not do this unless you have absolutely no alternative. Also you will want to place your board in there when the oven is cold otherwise the sudden temperature change could cause warping of the board and then you could be in real trouble. Do it for 10 minutes total I would say