LG 42lb5820 Won't Turn On with 3 Blinking Red Light

[dick_barton]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

That's the problem with replacing leds. You try to match them as best you can for colour temperature and brightness but until they are installed you cannot really tell.
Getting hold of a replacement led strip for that set and using the leds from it to replace your faulty ones would be one way to match them. Or contact Flocko on this site and see if he can help you.

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

im not sure where you got your replacement leds from but i see shopjimmy sell lg led kits 12 with diffusers at a good price they maybe a better light/colour match.

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

Thanks for all the replies. ShopJimmy did not have the strips for this model in stock (for quite a while now). Even the old LEDs (less bright) still had some non-uniformity when I looked closely so it is a bad design from LG then

Have any of you come across an LED LCD panel with a reflector film between the diffuser and LCD panel (as some models on YouTube did not have it)?

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

im not sure where you got your replacement leds from but i see shopjimmy sell lg led kits 12 with diffusers at a good price they maybe a better light/colour match.

I got some Innotek LEDs from China (which looked very similar to the original ones) and installed them individually (using SMD heatflow workstation) and glued the lens back on using superglue as I had a bit of spare time to play around with it .

[budm]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

Make sure to turn down the Backlights level to as low as you can so the LEDs will run cooler.

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

this is the kit i saw as they are for lg sets the colour match maybe better?
https://www.shopjimmy.com/replacemen...-set-of-12.htm

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

this is the kit i saw as they are for lg sets the colour match maybe better?
https://www.shopjimmy.com/replacemen...-set-of-12.htm

This the the strips for my model but there are out of stock. They are 6V, 200mA LEDs

http://www.shopjimmy.com/lg-6916l-17...s-8-strips.htm

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

which 6v eds did you choose from china? i dont think any of us have tried the 6v versions yet

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

I bought these 6V LEDs from AliExpress. I think all sellers are selling the same LG Innotek LATWT391RZLZK LEDs. Some how these ones are a bit brighter then the original LEDs.

Does anyone have the datasheet for the LG Innotek 3535 6V LEDs?

https://www.aliexpress.com/item/LG-I...608.0.0.PNnvfE

The measured LED backlight voltage was 211V which is a bit higher than 192V (6Vx32LEDs). Power supply board says 208V with 235mA.

I might experiment and try to drop the voltage down by 10-15V and see what happens. Does anyone have any suggestions on the best way to reduce the backlight voltage by 10-15V apart from using a 10W light bulb?

I hate working with lead-free stuff - to hot to my liking

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

maybe a resistor across the new leds somehow to drop the voltage/brightness ? as dropping the voltage on the whole strip wont the new leds still be brighter? im still learning myself maybe budm will have a idea too try out.

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

maybe a resistor across the new leds somehow to drop the voltage/brightness ? as dropping the voltage on the whole strip wont the new leds still be brighter? im still learning myself maybe budm will have a idea too try out.

It is a stupid back-light design to connect ALL the LEDs in series (like the Christmas decorative lights) so if 1 fails (open circuit) then the whole thing is dead. Putting a resistor in across the LEDs will work but it is too tedious. If I have to open it up again then I might as well replace them with the correct LEDs

[budm]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

Disregard, double post.

[budm]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

I bought these 6V LEDs from AliExpress. I think all sellers are selling the same LG Innotek LATWT391RZLZK LEDs. Some how these ones are a bit brighter then the original LEDs.

Does anyone have the datasheet for the LG Innotek 3535 6V LEDs?

https://www.aliexpress.com/item/LG-I...608.0.0.PNnvfE

The measured LED backlight voltage was 211V which is a bit higher than 192V (6Vx32LEDs). Power supply board says 208V with 235mA.

I might experiment and try to drop the voltage down by 10-15V and see what happens. Does anyone have any suggestions on the best way to reduce the backlight voltage by 10-15V apart from using a 10W light bulb?

I hate working with lead-free stuff - to hot to my liking

Are you measuring the 211V with ref to GND, if that is the case you are not reading the total Vf of the LED string. LED is current device, you drop the current through the LED to reduce the brightness, the power supply is the constant current source that will try to maintain constant current through the load, sot eh the load resistance change the the supply Voltage to the load will also change to maintain constant current through the load.
To read the total Vf of the LED string, you need to measure the Voltage between the Anode and the Cathode of the LED string.

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

It is a stupid back-light design to connect ALL the LEDs in series (like the Christmas decorative lights) so if 1 fails (open circuit) then the whole thing is dead. Putting a resistor in across the LEDs will work but it is too tedious. If I have to open it up again then I might as well replace them with the correct LEDs

i totally agree its getting the correct lg leds/colour match thats going too be hard unless you can find a cracked screen set with same model number or maybe one good led strip and swop leds over etc but means stripping it down again.

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

Are you measuring the 211V with ref to GND, if that is the case you are not reading the total Vf of the LED string. LED is current device, you drop the current through the LED to reduce the brightness, the power supply is the constant current source that will try to maintain constant current through the load, sot eh the load resistance change the the supply Voltage to the load will also change to maintain constant current through the load.
To read the total Vf of the LED string, you need to measure the Voltage between the Anode and the Cathode of the LED string.

I measure the Vf of the LED circuit and its was constant at 127V with various backlight settings.

I think I live with it and will wait for some cheap 2nd hand strips to come up for sale

[budm]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

127V Vf? But you said have 32 LEDs (6V Dual-LED), Is that correct? When you vary the backlight level, the current is changed and will be regulated to that setting, the Vf will change a little, but the Vdrops on the PWM Controlled will go up when Backlights is set to less, opposite when Backligts is set t higher level.

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

127V Vf? But you said have 32 LEDs (6V Dual-LED), Is that correct? When you vary the backlight level, the current is changed and will be regulated to that setting, the Vf will change a little, but the Vdrops on the PWM Controlled will go up when Backlights is set to less, opposite when Backligts is set t higher level.

Yep, 127V in VDC meter reading. It could be the PWM causing the multimeter to read such low value.

Could there be something wrong with the power supply board?

I gave attached a photo of the backlight distortion. You can still make out the distortion with the original LEDs as well. This project has taught me quite a lot about LED CD TVs (with a lot of the forum posters' help)

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

does the lg logo on the lcd screen look bad too? in the picture it dosnt look very clear looks like it has lines etc.

[Wildwind]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

does the lg logo on the lcd screen look bad too? in the picture it dosnt look very clear looks like it has lines etc.

No, picture is clear and it's a spinning logo and the camera had trouble in low light with the shutter speed.

[vinceroger69]

Re: LG 42lb5820 Won't Turn On with 3 Blinking Red Light

Thats ok then but yes the new leds certainly are brighter i wonder if its worth you emailing shopjimmy and see if they do the lg 6v version replacement led kits as hopefully they would of tested them and be the correct colour/brightness.

can you read any of the numbers etc from the bottom of the old led if it has any printed on it