Question LG 32LN5100 power problem

[vanguardviper]

Hi
I have a LED TV
Model : LG 32LN5100
there is a problem with power board (Model : EAX64905001)
after testing the board I figured that the Chopper circuit is dead , so I tried to replace it with these options :

• Viper12A
• 5L0380R
• DS0088 Module

all three methods managed to give standby light (with all voltages) still when trying to turn on , TV light (backlight LED) blink and return to standby .
I checked CAPS , Diodes , Resistors ... all seems to be good .
I've noticed that there is some voltage drop when turn on .
Voltages :
3.3V
11.8V
24.5V
Am I missing something ?
thanks in advanced .

 

[BEAUFORD_SAVAGE]

By chopper circuit are you talking about the the switching power supply?
A voltage drop of a small amount normal under load. Those voltages look good.

• Viper12A
• 5L0380R
• DS0088 Module

These parts mean nothing to me. They are probably unique to this manufacturer models for the most part.
With what little detail is included in your description, I would say the problem is probably on the main board processor board,
not the power supply.

By "so I tried to replace it with these options" I assume those options were actually replacement parts?
Changing parts by using the "shotgun method" never works. You need a solid reason to go replacing parts.

I did some leg work for you, Look here, I found your Make /Model with same issue!!
CLICK ON LINKS BELOW
YouTube link for YOUR MAKE/MODEL AND PROBLEM!!
BACKLIGHT ISSUE
PART 2
ANOTHER
JUST TYPE IN lg 32ln5100 IN YT SEARCH BAR AND GET A LOAD OF RESULTS.
If no luck, (which I doubt), read below.
You're on pretty solid ground ground to replace the main board.

 

[vanguardviper]

By chopper circuit are you talking about the the switching power supply?
A voltage drop of a small amount normal under load. Those voltages look good.

• Viper12A
• 5L0380R
• DS0088 Module

These parts mean nothing to me. They are probably unique to this manufacturer models for the most part.
With what little detail is included in your description, I would say the problem is probably on the main board processor board,
not the power supply.

By "so I tried to replace it with these options" I assume those options were actually replacement parts?
Changing parts by using the "shotgun method" never works. You need a solid reason to go replacing parts.

I did some leg work for you, Look here, I found your Make /Model with same issue!!
CLICK ON LINKS BELOW
YouTube link for YOUR MAKE/MODEL AND PROBLEM!!
BACKLIGHT ISSUE
PART 2
ANOTHER
JUST TYPE IN lg 32ln5100 IN YT SEARCH BAR AND GET A LOAD OF RESULTS.
If no luck, (which I doubt), read below.
You're on pretty solid ground ground to replace the main board.

Thanks for reply
firstly , yes I mean the switching circuit
secondly , the ICs that I tried are very known for replacing switching circuits in many boards (usually a mosfet and an oscillator ic)
I'm positive that the main board is working good cause I tried another power board and It worked well !
the power board has a switching circuit contains an oscillating IC (SC1S311) and a switching mosfet (MDF11N65B)
usually a switching circuit can be replaced by All in IC (that contains both oscillator IC and Switching IC)
for example VIPER12A has 8 pins (4 pins are Drain , 2 pins are Source , 1 for feedback and one for VDD)
I used this IC many times with no problems , but now I have 2 power boards and I'm trying to fix them !
I even tried to use external board for LED backlight , still the same problem .

 

[BEAUFORD_SAVAGE]

Did the YouTube videos not help you out in the troubleshooting? So you know that a different power supply board will work Right?
That means going into more depth troubleshooting the bad Power Supply board.
Bad caps are often the problem, in Switching Powers supply's, and will keep the
oscillating PS from switching.
Have you checked for any caps that have rounded off tops? Use the good board for comparison of where the circuit stops working
as compared to the bad board.
Not sure what else to say without having the board in front of me.

 

[vanguardviper]

Did the YouTube videos not help you out in the troubleshooting? So you know that a different power supply board will work Right?
That means going into more depth troubleshooting the bad Power Supply board.
Bad caps are often the problem, in Switching Powers supply's, and will keep the
oscillating PS from switching.
Have you checked for any caps that have rounded off tops? Use the good board for comparison of where the circuit stops working
as compared to the bad board.
Not sure what else to say without having the board in front of me.

I've seen YouTube videos that you shared and many other videos , they are all simple repair , usually a bad CAP or Diode or some jumper !
I've checked and replaced all CAPs on board , still the same problem .
I wish I have an identical board to compare , but sadly I don't .
one thing to mention , I've noticed that all ICs that I tried are getting hot , above normal , so I'm going to try another ICs with higher Amperage capability.
many thanks for reply!

 

[BEAUFORD_SAVAGE]

I came back after thinking about all you have said you have done. Don't take this to hard, but unless you know that Switching Power Supplys are not simple, but carefully balanced circuits, that require a special kind of capacitor, as explained below (only partially explained) , then you have effectively made the power boards irreparable. Just buy new ones and save yourself a big headache.



I DON'T recommend shotgun repair method! Or overating everything! The only component
you should be shotgunning is electrolytic capacitors. IF YOU ARE PUTTING IN CAPACITORS WITHOUT CONSIDERATION TO THEIR ESR, YOU ARE BUSTING THE CIRCUITS!! TAKE THEM BACK OUT!! AND REPLACE PROPERLYThey can cause things to overheat. Or cause switcher supplys to not oscillate. You don't need to overate their voltage, but by putting in FM rated caps, you are putting in a lower ESR cap. That will work much better over long periods of time. look those up in Digikey.com. FM series Panasonic caps. Look up Low ESR if you don't know what it is. YOUTUBE IS RIGHT ABOUT THE CAPACITORS!! But not the jumpers. If you go replacing semiconductors with different specs you are just asking for problems. Just stick with all electrolytic caps for now. Those are absolutely the most common failures in switching P.S.
Use your meter on resistors, diodes etc. Inductors very rarely fail. Don't replace critical Switcher circuit IC's with different types! These circuits are balanced at the factory, and you could be rendering boards useless. Then you will never find the problem! I HAVE BEEN DESIGNING AND REPAIRING SWITCHING POWER SUPPLYS FOR YEARS. If you don't want to listen, suffer the consequences.
I give up at this point.

 

[vanguardviper]

I came back after thinking about all you have said you have done. Don't take this to hard, but unless you know that Switching Power Supplys are not simple, but carefully balanced circuits, that require a special kind of capacitor, as explained below (only partially explained) , then you have effectively made the power boards irreparable. Just buy new ones and save yourself a big headache.



I DON'T recommend shotgun repair method! Or overating everything! The only component
you should be shotgunning is electrolytic capacitors. IF YOU ARE PUTTING IN CAPACITORS WITHOUT CONSIDERATION TO THEIR ESR, YOU ARE BUSTING THE CIRCUITS!! TAKE THEM BACK OUT!! AND REPLACE PROPERLYThey can cause things to overheat. Or cause switcher supplys to not oscillate. You don't need to overate their voltage, but by putting in FM rated caps, you are putting in a lower ESR cap. That will work much better over long periods of time. look those up in Digikey.com. FM series Panasonic caps. Look up Low ESR if you don't know what it is. YOUTUBE IS RIGHT ABOUT THE CAPACITORS!! But not the jumpers. If you go replacing semiconductors with different specs you are just asking for problems. Just stick with all electrolytic caps for now. Those are absolutely the most common failures in switching P.S.
Use your meter on resistors, diodes etc. Inductors very rarely fail. Don't replace critical Switcher circuit IC's with different types! These circuits are balanced at the factory, and you could be rendering boards useless. Then you will never find the problem! I HAVE BEEN DESIGNING AND REPAIRING SWITCHING POWER SUPPLYS FOR YEARS. If you don't want to listen, suffer the consequences.
I give up at this point.

I really appreciate your advice , and thanks for all suggestions .
Still I want to clarify some points :
I'm an Electronics Engineer , and have been working in this industry for about 15 years .
I'm very familiar with compatibility issues and defiantly wont replace anything without considering all part's specifications .
I've changed all capacitors and that didn't solve the problem , and that's why I asked in the first time !
I was hoping that someone had the same problem and could share experience .
on replacing switching circuit , I chose compatible parts (Voltage , Amperage , Frequency ... etc)
again , thanks for reply .

 

[BEAUFORD_SAVAGE]

Ahhh, I see, not speaking to a rookie. Gotcha! Don't I feel silly.
That's good to hear. I just answered a question about what this guy should do because he lost
his AC cord!!! So You see, not everyone has our backgrounds.
That said, using the Panasonic FM series capacitors for their exceptionally low Equivalent Series Resistance,
is exactly what switching power supplys love to run well on, for FAR longer than the manufacturers original caps did.
And I was thinking you may well have a capacitor that looks groovy and all, but is a problem anyway.
As far as Working on THAT exact power supply? Nope, can't say I have. If /when you find the issue, write back! I'm curious
to know what you have learned. I am a Electrical Engineer myself, I started with a Associate degree, got alot of experience,
then went back to school for my four year degree, and did so running my own repair business out of my home.
So I have a tad of experience myself. Good Luck!