I used this site a couple years ago and got great help, fixed 3 tvs. One of which I am having problems with again, first time it was a bad mother board. The tv stays outside under a covered porch with a cover on it when not in use. The tv started powering itself off after 2 or 3 seconds following initial start up. At first I could unplug it and after plugging it back in it would come on and stay on. Now it turn itself off no matter what. I can disconnect the tcon and after unplugging and plugging it back in all the backlights will stay on. However, if I just power on and off it will not come back on the led power light will just flash a couple times. In this state the pins on the psb show no readings. Then if I unplug AC and plug back in all the readings go to normal. At first I thought it was the tcon since lights stayed on after disconnecting, but now I realize the psb loses power on the secondary side if I just turn it off and on using the remote or the power button, thanks in advance and hope to get this back running in time for my super bowl party.
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Another LG, 55ln5100 power issues
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Re: Another LG, 55ln5100 power issues
LG LN series have high rates of backlight failure. Is the tv turning off completely or is the tv on but with the backlights shutdown? Without a led tester, you can monitor the voltage going to the strips to see if they peak up and settle.Last edited by neilc6; 01-20-2020, 04:43 PM.
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Re: Another LG, 55ln5100 power issues
1) We need good clear pictures of the whole backside of the TV showing all the boards.
2) You need to report all the Voltage readings of the power supply connectors that go to the main board when TV is OFF and when the power switch is activated, you MUST put down the pin name and the Voltage reading for EACH pin so we can easily spot the bad Voltage readings.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: Another LG, 55ln5100 power issues
With TV plugged in and without turning on TV the only 2 readings are 3.5v on pdmi2 and pdmi1, no other outputs on the connector. If I power off with button and back on all the readings stay the same. However if I unplug ac and plug it back in all the back lights come on and both 12v pins read 12v, the 24v pin reads 24.3 and both pdmi2 and 1 read 3.5. If I power off using the button it goes back to original state of no voltage readings other than the 2 pdmi pins
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Re: Another LG, 55ln5100 power issues
Originally posted by Redrebel10 View PostWith TV plugged in and without turning on TV the only 2 readings are 3.5v on pdmi2 and pdmi1, no other outputs on the connector. If I power off with button and back on all the readings stay the same. However if I unplug ac and plug it back in all the back lights come on and both 12v pins read 12v, the 24v pin reads 24.3 and both pdmi2 and 1 read 3.5. If I power off using the button it goes back to original state of no voltage readings other than the 2 pdmi pins
You will get the switched 12V/24V when PWR-ON control signal from main board is present.
You will get backlights when PWR-ON, DRV-ON, and PDIMs from main board are present.
So it looks like the main board not always sending out all the control signals.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
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Re: Another LG, 55ln5100 power issues
Originally posted by budm View PostHow about the PWR-ON (PS-ON) and DRV-ON (BL-ON)?
You will get the switched 12V/24V when PWR-ON control signal from main board is present.
You will get backlights when PWR-ON, DRV-ON, and PDIMs from main board are present.
So it looks like the main board not always sending out all the control signals.
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Re: Another LG, 55ln5100 power issues
"Press the power button and no backlights come on but I have 3.3 on the DRV-on pin. and still 3.5 on both pdmi pins." So what is the PWR-ON (PS-ON) in that condition? I do not see any report on the PWR-OM pin, no PWR-ON = no 12V/24V.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: Another LG, 55ln5100 power issues
I was testing the back of the plug assuming they were ps-on and dvr were connected. I'll attach a picture. Weird thing just happened, standby light was on, I pushed power button and no voltage readings other than pdmi, standby light went off and now standby light won't come back on and unplugging ac doesn't help, backlights will not come back on nor will the standby light. I still get 3.5 on pdmi but no other readings
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Re: Another LG, 55ln5100 power issues
Originally posted by Redrebel10 View PostI was testing the back of the plug assuming they were ps-on and dvr were connected. I'll attach a picture. Weird thing just happened, standby light was on, I pushed power button and no voltage readings other than pdmi, standby light went off and now standby light won't come back on and unplugging ac doesn't help, backlights will not come back on nor will the standby light. I still get 3.5 on pdmi but no other readings
So main board is not sending ALL the needed control signals for the TV to work at this point.
Control signal: <1V = OFF, >2 ~ 3V = ON.Last edited by budm; 01-21-2020, 09:57 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809
Comment
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Re: Another LG, 55ln5100 power issues
Not your tv model number but maybe worth a watch
https://www.youtube.com/watch?v=kbjNq1AyF00&t=362s
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Re: Another LG, 55ln5100 power issues
Originally posted by vinceroger69 View PostNot your tv model number but maybe worth a watch
https://www.youtube.com/watch?v=kbjNq1AyF00&t=362s
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Re: Another LG, 55ln5100 power issues
Originally posted by budm View Post"Press the power button and no backlights come on but I have 3.3 on the DRV-on pin. and still 3.5 on both pdmi pins." So what is the PWR-ON (PS-ON) in that condition? I do not see any report on the PWR-OM pin, no PWR-ON = no 12V/24V.
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Re: Another LG, 55ln5100 power issues
Check D201 and the rest of the diodes, check for bad/cold solder joints on bottom side of board, look closely at the solder joints of components on heatsinks and on transformers, sometimes they look good but are bad or loose.Last edited by nomoresonys; 01-22-2020, 08:28 AM.
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Re: Another LG, 55ln5100 power issues
Originally posted by nomoresonys View PostCheck D201 and the rest of the diodes, check for bad/cold solder joints on bottom side of board, look closely at the solder joints of components on heatsinks and on transformers, sometimes they look good but are bad or loose.
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Re: Another LG, 55ln5100 power issues
Did you check all the diodes on powerboard? just check m in diode mode, should get a reading in one direction usually .2~.7 or so then reverse the test leads and should read OL, simple diode testing there: https://www.youtube.com/watch?v=mMXDa5hVzXA
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