LG42PX4RV-2A no 5v stb

[topng]

hi all
today I received from a friend TV does not turn on.
i chack it and I checked and found that the improper component a6151 i replace it .
i chack with esr meter and find that c122 and c123 with high esr i replace them with new one .

now i get 5vstb but whan i plug the video board the 5vstb becomes 3.1 and jumping up down.
and red led blinking
Thanks for your help

[topng]

Re: LG42PX4RV-2A no 5v stb

?

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

A current consumption on 5 volts plug the video board ?

[topng]

Re: LG42PX4RV-2A no 5v stb

yes whan i plug the p1001 the voltage is drop to 2.6-3.81

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

It is necessary to check the resistance of the load on the 5 vstb video board

[topng]

Re: LG42PX4RV-2A no 5v stb

Ic check it is 2.3k ohm

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

Now check on the power supply Z121, PC121, C122, R122, R130 and show foto this area

[topng]

Re: LG42PX4RV-2A no 5v stb

ok i will test and update.

[topng]

Re: LG42PX4RV-2A no 5v stb

Hi what do I need to check ?

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

Measure the voltage on the Z121. A- pin 3 (hot ground !) with pin 5 of about 300 volts. B - pin 3 to pin 2 of about 20 volts

[electricboyo]

Re: LG42PX4RV-2A no 5v stb

Check the following 2 resistors on the power supply:

R130 (red-red-gold) should be 2.2 ohms
R203 (red-red-silver) should be 0.22 ohms

These are flameproof resistors. When overloaded by a short circuit, they act like fuses and become open circuit. Both resistors in your pix have little black spots on them: That's usually what they look like when burned out. When you look real close you will see that there is a little bit of a hole burned into the resistor's coating. On the other hand, if the black mark is simply from a marking pen, and the resistor tests good with a meter, then there is no problem here.

-EB

[topng]

Re: LG42PX4RV-2A no 5v stb

Hi
From 2 to 3 I get 12 to 15 it jump
From 3 to 5 I get 300v
I replace r130 it test good but just in case

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

Replace С121 and C122

[topng]

Re: LG42PX4RV-2A no 5v stb

R203 good

[topng]

Re: LG42PX4RV-2A no 5v stb

Replace c121and c122 the same problem

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

"From 3 to 5 I get 300v" jump or not

[topng]

Re: LG42PX4RV-2A no 5v stb

300 to 302 jump

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

Measure the voltage on the Z121 pin 3 to pin 4

[topng]

Re: LG42PX4RV-2A no 5v stb

From 0 to 4.7 jumping

[kasfamily]

Re: LG42PX4RV-2A no 5v stb

Replace the TL431 (I do not see its position number) which stands in the cold part of PC121