LG/Optica 7074c / 42" SmartTV

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

its android as i thought. so the 2GB SD was extra memory to save data or recording ... any way you need to test yours led one by one with DMM as diode method, you can use 7030 LED Type 6 volts 100 pieces less than 6 USD at aliexpress... but please calculated with finger yours LED are thy 60 or less.. thanks

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

8 vr1 - led 51
7 vr2 - led 41
6 vr3 - led 31
5 vr4 - led 21
4 vr5 - led 11
3 vr6 - led 1
2 nc
1 v - led 60

LED 14 is lighting a little bit when tested in diode mode

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

you need to test them out of the set.. ( not connected to tv ) one by one direct at the LED Pins in opposite probe as diode DMM, they will not lighting up, just they give you the diode Value, which it will be between 740-780, you have some keeping lighting on as you listed before, the test value of them take it as references value to others

if this test all okay, then the fault not at strips or LEDs.

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

doubled

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

I'm sure LED 14 is causing the problem, a few look a bit scorched and there seems to be a pattern to it, 14 23 33 43 54 look slightly burnt, Half of LED 14 lights up when tested in diode mode, this is the only LED that does this. Starting at the connector side i get 840 and the max reading is 1050, it seems to increase as i move down the strip, this is testing each diode individually, i have been testing them out of circuit

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

himm yours LEDs seem had different way build in Diode, i just took close on yours photo 1 JPG, there is joint pin at the middle of the LED so look at the photo, can you confirm it?

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

i can see it but this does not connect to the board, i think they are soldered under the LED to help with heat dissipation.

I have attached a datasheet

[budm]

Re: LG/Optica 7074c / 42" SmartTV

BTW, the pin 1 on the LED connector is the B+ that feed the common ANODE of all the LED strings inside the panel, the VR1~V6 are the CATHODE return for each LED string, so if there is any high impedance or open circuit in the string then you will see very low Voltage on the Vr return pin.
And if you look at the Voltage rating of that filter cap for the Boost converter connected to pin 1, you will see that it is only rated at 100V, those LEDs are Dual-LED connected in parallel inside one package
(see attached photo), 20 LEDs x 3Vf = 60V for the total VF of one string then + Vdrops on the PWM MOSFETs + current sensing resistor.
If the LEDs are dual-LED in series, the you will need 20 x 6Vf =120 V +Vdrops for MOSFETs and Vdrops of current sensing resistor, but as you can see, the Voltage rating of the filter cap is only 100VDC, which BTW, what DCV do you get on that cap?

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

When i power the set on its 23v for a second then goes up to 75v

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

No, yours LEDs wasnt 7030, i just mention them as size and double led 6 volts.

i was confused, you should explain that the photo you posted at POST No 9 wasn't belong to yours set, as they have 55 each.. so this why i asked on the No.
so you have total 60 with 7 line of socket mean you have 6 groups each 10 and one + common to all groups. but we need to be sure of the zenner Diode of this LED how it built in, Normal LED the Black joint point ( of Zenner ) will be at one side of the LED, you have this POINT at the middle. can you take out the suspected one No 14 out so we will know exactly what we have.

[budm]

Re: LG/Optica 7074c / 42" SmartTV

When i power the set on its 23v for a second then goes up to 75v

That is correct for 100VDC rating cap and for the B+ feeding the LED string anodes.

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

okay, confirmed 7030 innotek from LG. here you can get them

http://www.aliexpress.com/item/LG-LE...2-f513c34b6476

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

Thanks for the help guys, i will order the LED's and update in a few weeks, 20-40 days for shipping, i dont want to use anything but the exact parts, not worth the risk with the heat these things put out.

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

I got the LEDs and replaced 6 that looked physically burnt but now when i power the tv on i get a high pitched noise from the inverter board and most of the LEDs go out again.

[vinceroger69]

Re: LG/Optica 7074c / 42" SmartTV

have you got all the leds fitted right anode and cathode wise

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

yes, i have double and triple checked

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

Every time i test it i'm killing a few LEDs each time, i'm wondering if these are duds or the problem lies somewhere else

[vinceroger69]

Re: LG/Optica 7074c / 42" SmartTV

I wonder if the psu is putting the wrong voltage out and blowing the leds? if this is possible of course and also as you say the leds maybe duds and are not the correct voltage/amps they are stating they are.

[Diah]

Re: LG/Optica 7074c / 42" SmartTV

Every time i test it i'm killing a few LEDs each time, i'm wondering if these are duds or the problem lies somewhere else

the killed one from the old original one. right? get rid of them and replace all at once so you have new strips

[badcaphunter]

Re: LG/Optica 7074c / 42" SmartTV

Problem solved, must have been dodgy LED's or a bad connection. TV is back up and running... after killing 20 LED's