Repair inverter Board PPW LE32RG-0 on LG 32"

[edugimeno]

Hi There!
I have this TV that's missing backlight. I went ahead withount even removing the cover and ordered a set of 4 LED strips.

Today they've been delivered and before I took out the LCD panel I spent a couple minutes taking a couple measurements. To my surprise I wasted my money with the LED strips as I checked and there's no voltage in the output of the LED inverter board. Expected 125 v aprox in the output and I got ZERO

Inputs to the board seem OK as I get stable 25V DC

I can't find the schematic for this board, but there's probably someout out there able to talk from experience and know what tends to go bad on these boards?

Thanks in advance!
Eduardo

[edugimeno]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

I checked the large coil/transformer in the center (can't find PN for this neither) and it had 0 ohm between all 4 legs. Is this normal? I would expect LOW OHM for each pair of 2 legs...

[R_J]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

The board monitors the led current, if there is an open circuit in the led string the output is shut down. If the transformer was shorted it would blow the input fuse.

[edugimeno]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

The board monitors the led current, if there is an open circuit in the led string the output is shut down. If the transformer was shorted it would blow the input fuse.

So you think the led strip is open circuit? I would expect at least a short "testing" pulse to determine the current thru the strips
I found an SMD fuse in the inverter board and it's fine

Is there a way to determine the status of the LED strips before opening the other side? Just from the wires that plug them into the inverter board?

Hopefully it's just one led strip as I already bought them!!

Thanks

[R_J]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

monitor the voltage across the led plug going to the string to see if there is a voltage, it might happen very fast.

[edugimeno]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

monitor the voltage across the led plug going to the string to see if there is a voltage, it might happen very fast.

Yes, there has been a quick spike, maybe under 0,5s, not measurable in actual numbers by my multimeter, but it has a digital bar on the bottom that showed a sudden jump up
Should I go ahead and remove the panel to check the LEDs?

Thanks

[R_J]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

those circuits are quick to check the current and voltage and to shut down in an instant for protection. Unless you have a way to connect the new strips together and then to the board I don't see any other way to check the led's. Once the lcd panel is removed (remember the exact order and orientation of the diffusers) and you have access to the led's you can check them without reinstalling the lcd panel to test them.

[edugimeno]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

Ok I already have it open These leds don't have the usual test pads by each LED so I will probably just change them all ( I bought a full set of 4 strips) and see how it goes


Thanks

[edugimeno]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

Ok, topic closed... I swapped all the strips, turned over, plugged everything back in and it worked perfectly!
Now the openings for the LEDs in the back white reflective paper doesn't match for 20 of them so I need to do some cutting work, but it all looks good now

THANKS!

[R_J]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

Good to here it's almost finished. now take your time reassembling the panel.

[edugimeno]

Re: Repair inverter Board PPW LE32RG-0 on LG 32"

Finished now, all aseembled and I have a great working TV again.
Note if anyone else is swapping led strips on this TV: Pay attention to the position as some TV sets (like this) have 2 sets of strips, and strip 1&3 have 5 center leds shifted to the left while strips 2&4 have 5 center leds shifted to the right...

How did I realize? I didn't see that so I assembled them all in a random order (exactly 100% reversed...) Then I realized that the reflective paper wouldn't match the holes on 5 led on each strip.

Too late to lift the strips back up without risk of detaching one led when the strip bends, so I ended up making new holes (bad looking hack...) to those 20 leds.

Now I understand why the end plug of each original strip had different colors (gray or white)

Anyway, it's all back to working. I lowered the BL to 50% to prevent this to happen again

THANKS again!