LG Flatron EW224 - No backlight

[mattpd]

I have a EW224 Flatron monitor that shows a display, but does not have a back light. This model is has an LED back light. Luckily for me, I have a working version of the exact same monitor, so I swapped the power and logic board into the dead monitor, but still I have no back light. The only conclusion that I can make is that the LEDs themselves are faulty.

I have replaced CCFLs in monitors before, but never LEDs. Is there anything I need to look for when I crack open the LCD screen? Is it a simple job to replace LEDs, or is it not worth the time?

[budm]

Re: LG Flatron EW224 - No backlight

The y use the very delicate FFC (Flat Flexible Cable) that can easily be cut or nicked into and cause it to short out to the chassis. Since the LEDs are connected in series, if one is open then the rest will not light up. So those are some of the thing to look for, you can try measuring each of the conductor pad on the FFC and the chassis to see if any one of them is shorted to the chassis. You also have working unit that you can do some resistance reading comparison.

[mattpd]

Re: LG Flatron EW224 - No backlight

Thanks, I will crack it open tomorrow and take a look

[Iceman2]

Re: LG Flatron EW224 - No backlight

Hi guys I have problem, i buy this monitor and in the power board there is missing
C303( i dont know the value and voltage:/ The number for board is EAX63028703/0 and version HIGH. Meaby you have service manual or know values

[lexwalker]

Re: LG Flatron EW224 - No backlight

Hi guys I have problem, i buy this monitor and in the power board there is missing
C303( i dont know the value and voltage:/ The number for board is EAX63028703/0 and version HIGH. Meaby you have service manual or know values

Is this a working monitor when you bought it? Pictures of the area around that C303 capacitor, as well as description of the circuit leading to C303 capacitor (possibly a partial schematic) may help us guess. Sometimes there are empty spots where the manufacturer simply changed their minds at the last moment and decided not to put a component there..

[Iceman2]

Re: LG Flatron EW224 - No backlight

I buy the monitor for repair and when i dissasemply i see that someone desolder the C303 and other capacitors meaby for test, solder the rest but no the 303. Monitor is dead when i buy, no led power I check the mosfet 18T10GH and is shorted, C303 is connected to that 18T10GH with positive leg

[lexwalker]

Re: LG Flatron EW224 - No backlight

I buy the monitor for repair and when i dissasemply i see that someone desolder the C303 and other capacitors meaby for test, solder the rest but no the 303. Monitor is dead when i buy, no led power I check the mosfet 18T10GH and is shorted, C303 is connected to that 18T10GH with positive leg

Not good enough description. Please post pictures of that area. If possible, some partial (self-drawn) schematics as well. Is that capacitor surface mount type, or through hole type? Is this MOSFET in the inverter section?

[Iceman2]

Re: LG Flatron EW224 - No backlight

No the capacitor is normal through hole Electrolytic Capacitor, Su'scon shit The mosfet is connected to the led driver mp3399ey, this is led screen. I check all components in the upper layer, capacitos,diodes... all ok

[selldoor]

Re: LG Flatron EW224 - No backlight

Does it look like Q300 has been removed also.?

Looks like a big mosfet?
http://mlb-s1-p.mlstatic.com/placa-f...9_032013-O.jpg


and lots of other components

[lexwalker]

Re: LG Flatron EW224 - No backlight

No the capacitor is normal through hole Electrolytic Capacitor, Su'scon shit The mosfet is connected to the led driver mp3399ey, this is led screen. I check all components in the upper layer, capacitos,diodes... all ok

Looks like part of a boost converter, with that inductor/choke then followed by a rectifier diode. Could be anywhere from 4.7uf to 47uF (or higher). The voltage rating for that capacitor could be at least 100Vdc (and higher). According to MP3399EY datasheet sample schematics, its 22uF 100VDC although the inductor used was 33uH (while this board looks to be using 47uH)...

[Iceman2]

Re: LG Flatron EW224 - No backlight

I remove the Q300 mosfet, test it and is shorted i upload the pictures after remove yup the inductor/choke is 47uH i test and is 45uH The diode is good I dont have that capacitor value, if i have i test the board replacing for good brand I emai a guy who sell identical board on ebay, the picture is above and i dont see the values

[Iceman2]

Re: LG Flatron EW224 - No backlight

I remove the Q300 mosfet, test it and is shorted i upload the pictures after remove yup the inductor/choke is 47uH i test and is 45uH The diode is good I dont have that capacitor value, if i have i test the board replacing for good brand I emai a guy who sell identical board on ebay, the picture is above and i dont see the values

update:

Hi guys i repair that monitor, the capacitor is 100V 47uf, 5v is stable