LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

[R_J]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

any possibility I bypass standby and give 3.5V externally?

All this would do is supply 3.5v to the main board, the power supply will never operate without the standby circuit working first. The standby circuit also supplies vcc to the other ic's on the power supply.

[dskall]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

You have a schematic that have the voltages. Just go around that IC and check for wrong voltage.

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Does anyone happen to have the schematic for this power supply board? It's an EAX62865401. Thanks

[lotas]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Does anyone happen to have the schematic for this power supply board? It's an EAX62865401. Thanks

Look, it's not her.

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Thanks. I'm trying to figure out why the relay isn't getting voltage to kick on. I'm not getting my 3.5v stby so I have to figure this out first. It's just alot easier with the schematic. Thanks again

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Ok so it looks like my board is ok. Looks like it's gonna be the backlights. Will check for correct voltages first going to backlights.

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Well it might be the mainboard. I only have 36v on the LED+ Pins on p202. Nothing on the others. 36v is low. What should I have here for the LED's?? If I have nothing on the DRV ON pin, would it be something on the main board?

[R_J]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

If the backlights were working you would have 53 volts on P202 LED+, but if the backlights are bad (very likely) the backlight driver circuit will go into protection and you will only have the base 36volts on LED+
What is the voltage on P201 EROOR (that's how it is spelt) pin? If there is a backlight error ic801 will likely tell the main board to turn off the DRV_ON signal.
Monitor the DRV_ON pin when the tv is first turned ON and see if this pin is 3volts before going to 0

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

I will check this when I get off this afternoon. I guess I need to check the backlights first with backlight tester to see if they even come on. I forgot to do this. I will let you know what I find. Im hoping it is the backlights and not the mainboard. Thanks for the reply.

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Ok so I don't get much on that DRV_ON pin. In stby I have nothing (5mV). When I press power on it only jumps up to 39mV. So main board must not be sending the drive signal. I did test backlights with a tester and I can get them to light up. What's crazy is I tried the jump method with resistor and main board unplugged and I can't them to light. They light with a led tester but not when stby pin is jumped to Drv_on pin. Unless I'm using wrong value resistor. I read 2 different values. Someone said 200 ohm to 500 ohm. Another person said 10k.

[R_J]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Backlight testers are not reliable, they only supply about 30ma of current. I don't know how many times I here that the backlights must be ok because the tester light them up. One bad led that fails when the string draws about 130ma and the supply shuts down.

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Good to know. Do you think I should remove front and check the LED strips individually?

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

I forgot to mention the Eroor voltages. 0v when in stby and 2.1mV when powered on.

[nomoresonys]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Don't worry about 2.1 millivolts it's basically the same as 0 volts.

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

So I redid the jumper test with main board unplugged and my backlights came on. So now I know it's the mainboard. From what I'm reading, it really can't be fixed other than the baking/reflow. Any other suggestions?

[nomoresonys]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

I think so, can try a diy reflow of the bga chip, really not much to lose, there's a ton of videos about it on youtube, some are better than others of course.

[nomoresonys]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Here's an interesting method, some use a little no-clean flux on 3 sides of the chip and try to let it flow under the chip: https://www.youtube.com/watch?v=ZDQNOU2w_ek

[nomoresonys]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

A temp probe would be very handy so you can tell what's going on, otherwise it's just guesswork, then you just get the temp up to melt the solder then slowly back off the heat to try to avoid thermal shock, I think whats cool about the light bulb over heatgun is you won't be getting thermal shock on the heat up because it will be slower than blasting with a heatgun, specially one that might not be tayloered for the job, just one temp probe there, prolly many others on there too: https://www.ebay.com/itm/29390306772...Bk9SR9KZyJTaYQ

[nomoresonys]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Here's Bob with a diy station, not everyone will want to make this but notice his profile, on this particular one, notice he goes to 200, solder starts to melt, he then goes up to 225 before backing off, didn't notice what kind of solder was used on that job, so just look up what solder was used on the chip, was probably the usual lead free crap they use, so prolly around 220c to start melting then maybe go to 240 or so then back off, with eithr method: https://www.youtube.com/watch?v=4Hl7-xPg2Sg

[GMAN6325]

Re: LG TV 49LW5700 does not power no Standby Voltage(PSU EAX62865401)

Well I have the TV up and running. I decided to do the reflow because the tv is old and not even worth paying $100 for a new mainboard. I added flux around bga chip and other chips. I slowly heated each chip and gentlty pressed down on chip every so often. After doing this, I re-installed the mainboard and voila. The TV works. Not sure how long it will last but hopefully the solder melted enough and the chip has a better connection. Thanks for all the suggestions.