I get a flash of blue screen when I power on the set.

so working on super old 2007 PC monitors. and no PC connected."? it is NOT ANY LED BACK LAMP monitor here.
came new with XP PC's.
the monitos all good to sleep mode if no PC vidoeo connected.
in the usa, even by law, (energy star)
how ever lacking a PC, the screen will show "no signal entering sleep mode"
VGA monitor.
LED = blue on, amber sleep, LED out, oFF.
NO 1080P mode allowed, (so common now) <<<< big clue here.
set the PC to 1024 x 768 (to test ) 60Hz.
using a flash light (torch) tool,.
turn on Monitor, see blue LED
point flash light to screen, see data, now, on sceen in the beam
now you now CCFL backlamps are dead. as most are this old.


Display Modes (Resolution)

640 x 350
720 x 400
640 x 480
800 x 600
832 x 624
1024 x 768
1152 x 870
1152 x 900
1280 x 1024
1440 x 900

proof BELOW. A FREE MANUAL TOO.
page 47, see 4, CCFL jacks and HV supplies here 600VDC
free service manual with full schematics and BOM

https://elektrotanya.com/lg_w1934s_flatron.pdf/download.html


in my shop I have VGA signal generator to maKE WORK EASY.

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hi, the most probably is broken one of neon lamps that illuminates led display .you can check that when you turn it on and flashes, see if one side of screen is brighter then other. also,it can be that power supply in led display got weakened and haven`t got enough power,but that is job for service like any bigger failure.
this is not the only answer,there is always several solutions but you have to give more informations about malfunctions. good luck!

Check filter caps in power supply.

There are two places to look for the problems, the backlight inverter board and the power supply. Look at the power supply first since it is easier to get to, look for burnt parts, bad capacitors, etc.
http://en.wikipedia.org/wiki/Capacitor_plague
Please post back what you find.

I JUST GOT HOME AN TRIED TO TURN MY JVC PLASMA TV ON. THE TV WILL NOT TURN ON. EVERYTHING ELSE HAS POWER TO INCLUDE THE TV BUT THERE IS NO PICTURE OR SOUND. BLANK SCREEN. THE BLUE POWER LIGHT IS FLASHING ON AND OFF. THE MODEL NUMBER LT-42P789

You most definately have bad capacitors in the power supply. try and get it repaired as soon as possible, not an expensive repair that iv'e seen.

Hi , I have the same problem with my LT-42X688,so i called the service of my extended warranty provider . the TV technician just left and told me the motherboard is the problem. he said its the third one this week he has seen with the same symptoms. he ordered the motherboard and i've got to wait 5 to 7 work days before the part will be in . I will keep you posted when the guy will return.

how do you flash the firmware using pc. can u tell the procedure

It sounds funny but, unplug the set for 30 seconds to allow the TV to reset then see if the problem still is there.