LG 42ld450 blinking red light

[microvibe]

have an lg 42ld450

the power light just blinks nonstop and screen has "LG" "lifes good", thats all it does. any ideas where to start? was told its main board but must be a way to fix that instead of replacing.

has anyone ever seen or heard this problem, btw does someone have a service manual for this model?

thanks

[microvibe]

Re: LG 42ld450 blinking red light

the red light doesnt actually go completely off, it shows the lg boot screen then flicks off and back to boot screen the longer i leave it doing this boot loop the image starts getting distorted. could the main board firmware be corrupt and its not booting up or possibly the main chip fried? i have good voltages frompower supply to main board.

[budm]

Re: LG 42ld450 blinking red light

Can you see any 3-pin voltage regulator ICs on the main board?

[microvibe]

Re: LG 42ld450 blinking red light

here is some pictures not sure what if any regulators on this board

[microvibe]

Re: LG 42ld450 blinking red light

actually removed board and there is 3 regulators on back side, 1 with middle pin clipped and 2 others with all 3 pins attached, how can i test them without power or is that not possible

[microvibe]

Re: LG 42ld450 blinking red light

voltage regulator #1
pin 1 -0.0
pin 2 1.23
pin 3 3.22

regulator # 2 it hasmiddlepin clipped
pin 1 3.23
pin 2 0.0
pin 3 2.45

regulator #3
pin 1 0.0
pin 2 1.77
pin 3 3.22

[tom66]

Re: LG 42ld450 blinking red light

What's the part number on each regulator?

[microvibe]

Re: LG 42ld450 blinking red light

voltage regulator
#1 eh11a
022j93

#2 az2940d
-2.5e1
036j29

#3 010110
17-18

i cant see number three's info very well so first line may not be correct

[tom66]

Re: LG 42ld450 blinking red light

They all appear slightly low; this is quite likely to be your multimeter at fault so can you try changing the battery, and/or a using different meter?

[microvibe]

Re: LG 42ld450 blinking red light

i will replace batteries its probably time, i should add that it looks like screen back lights flick on and off durring this boot loop and there is high pitch noise from main board everytime it does this reboot. this noise comes every 5 seconds or so in sync with the front light dimming and the back lights just flash briefly.

[RJARRRPCGP]

Re: LG 42ld450 blinking red light

Sounds like it keeps losing power briefly thus cycling.

I had this happen to my Acer LCD monitor, because of a poco issue.

I realized that it keep going out and kept displaying the Acer logo, because of a freaking semi-outage.

[microvibe]

Re: LG 42ld450 blinking red light

the longer i let it keep cycling the logo on screen starts to distort and get red white green pixels always changing and the image shifts. i cant find fuses on the main board

[tom66]

Re: LG 42ld450 blinking red light

Sounds like you have BGA defects -- this may not be fixable without replacement of the entire main board.
I wonder if the RS232 port will spit out anything interesting?

[microvibe]

Re: LG 42ld450 blinking red light

i did some more testing left unit cycling for 30min, the heatsinks by the inverter transformers get very hot the pannel shield on far left and right of tv also get hot. i tested voltages on power supply going to main board, the 20v is 20.5, the 12 volt is 12.08 the 3.5 volt is 3.35 the p-dim is 3.22 and drops to 3.08 when it cycles, the A-dim is 3.08 the inverter on/off is 2.92 and on the pin labled error its .03v. i dont know what voltage the p-dim or a-dim supposed to be or what the inverter on/off should be.

[tom66]

Re: LG 42ld450 blinking red light

Those voltages all look OK, but testing right now is irrelevant if your meter battery is low.

[microvibe]

Re: LG 42ld450 blinking red light

i changed the batteries already then tested the batteries i took out and both are 1.54v not a battery issue.

[microvibe]

Re: LG 42ld450 blinking red light

i am debating on just ordering replacement main board, still concerned about the heat, the power supply heatsinks get real hot and same with entire metal shield covering the backlights would being stuck in boot loop drawing full startup power cause this heat issue it gets really hot after about 30min. as for main board i have no idea where to start with troubleshooting, i did trouble shoot the few areas mentioned but they all seem good, i was thinking of having the chips reflowed but not sure that would help.

[microvibe]

Re: LG 42ld450 blinking red light

forgive allmy newb questions this second lcd i workedon, first had main board,t-con,2 inverter boards,psu. this tv just has main board,psu/built in invertersand 2 buffer boards.

i noticed when powered up backlights come on , one buffer board has blue light other buffer board doesnt have blue light. the one that lights up is on the left looking fromback. the blue does go out after cplseconds and doesnt come back on, question is should the buffer board on right light uptoo? another question how do u get those buffer boards out

[microvibe]

Re: LG 42ld450 blinking red light

well TV repaired, was bored today wanted to try onelast thing before ordered newmain board, since i have had laptop mother boardes reflowed before i decided to throw this main board in the oven on hi broil for 5min. let cool 30min and now TV is working. watched a 90min blu ray still going lol. guess i gotlucky on this one

[tom66]

Re: LG 42ld450 blinking red light

Reflow might temporarily sort it out, but it is rarely permanent. Did you use flux?