LG 42LE5300-uc no power.

[capwizard]

LG 42LE5300-uc the one I tested LEDs screen worked good, relay click, AC current stop at 0.244A, nextstep jump 3.5v to power-on and DRV-on, screen lightup (pic3), this one T-con is in the screen, gonna be the motherboard, order one see what will happen, will update.


LG 42LE5300 service manual:
https://www.electronica-pt.com/esque...artdown/24431/

PS: red mark is for easy to distinguish the pinouts. WHY, no use the resistors? because not necessary, no problems for me so far so good.

PS: scree has been tested over here, took me less than 3 min.
https://www.badcaps.net/forum/showthread.php?t=59327

[budm]

Re: LG 42LE5300-uc no power.

https://www.badcaps.net/forum/showth...ted#post713400

I always suggest to use resistor just in case the wrong connections are made like this one in post 108.

[capwizard]

Re: LG 42LE5300-uc no power.

Thank you, I think you just saved my life again, I did put 3.5v to DRV-on(pin4) missup with V-sync(pin5), lucky nothing happened, what happen the TV is 80", I promise I will use resistors from now on, no more lazybones.

[capwizard]

Re: LG 42LE5300-uc no power.

All men make mistakes, but only wise men learn from their mistakes....

PS: red marker mark is for easy to distinguish the pinouts

pic1-4 : 3.5v to power-on and 12v shows powersupply is on. R=6.8k

pic5 : 3.5v to DRV-on R=6.8k the screen not come on because not enough current to drive DRV-on, change to 3.9k is the same result then I put a piece of wire it work..... WHAT.... you did that again...NO...NO.....this one is for laboratory experiment.....

pic6-9 : change 12v to DRV-on R=6.8k screen come on.

Reference:
look at 4:00
Why use Current Limiting Resistors | AddOhms #8
https://www.youtube.com/watch?v=81zNcctopBI

PS: At 4:30 use LM317 precision current limiter to drive LED is Budm's idea and basically the principle of "Poorman's LED TV Backlight Tester".

[budm]

Re: LG 42LE5300-uc no power.

I use the value between 330~1K Ohms range which will limit the shorted current to 5mA (5V supply with 1K, 15mA @ 330 Ohms), the current is very low so it will not damage the power supply if the jumping is done wrong.
Most Command receiving signal pin has 1K resistor to feed the switched Transistor, see PS diagram fro typical set up..
So if the Transistor has low Beta, then it may not be turned on hard enough if you use too high of the resistance. The resistor is used for protection in case it is connected to the wrong pin.

[capwizard]

Re: LG 42LE5300-uc no power.

"330~1K Ohms range which will limit the shorted current to 5mA (5V supply with 1K, 15mA @ 330 Ohms)"

3.5v / 1000ohm = 3.5mA
3.5v / 330ohm = 10.6mA

PS: ive used 3.5v / 6.8kohm = 0.5 mA, YES, It is too low to drive DRV-on.

I had learned one more lesson and tips.....

Put A 330 Ohm between (3.5v , DRV-on) YES, screen lightup....

PS: From here you know one of my secret is I never use current limit resistor before...

[budm]

Re: LG 42LE5300-uc no power.

Typical command receiver circuit.

[capwizard]

Re: LG 42LE5300-uc no power.

RB858 100ohm That is lower than I thought was! more and more low voltage applications, the current limit resistor will be lower than what we think is.


Microchip announces a series of I2C EEPROM devices with the lowest operating voltage available on the market. The 24VLXX series of devices has an operating voltage down to 1.5V for both read and write operations, with a very low operating current of less than 400µA.

[budm]

Re: LG 42LE5300-uc no power.

That Base resistor can be from 100 Ohms and up to 4.7K (sometime as high as 10K), it all depends on the Base to ground resistor (it will have around 0.6Vdc that Base-Gnd (Emitter) resistor of that circuit) and the Beta () of the Transistor to insure that the resistor will be fully on to allow enough current for the LED inside the OPTO.

[capwizard]

Re: LG 42LE5300-uc no power.

The transistor is the fundamental building block of all modern electronic devices, what happen that was A MOSFET or IGBT? Does they have β gain or lower GATE (Base ) resistor?