LG Flatron 1915S monitor display fault.

[stuart06]

Hello.
Any advice or guidance concerning the following problem would be greatly appreciated please.

Switch on the PC and there's a flash of an image indicating the power status of the monitor followed by a black screen,then a similar flash of an image of the boot logo screen followed again by a black screen,to be followed again by a flash of an image of the BIOS screen again the black screen and then finally a flash of the image of the Windows logo then a black screen.
The power LED on the monitor remains green throughout and with the room darkened the image of the Windows desktop is vaguely visible on the monitor using a lamp positioned in front of the monitor.
If I switch off the power to the monitor while Windows is loaded and switch the monitor back on there is again a flash of an image of the Windows desktop followed by the black screen.(Image still visible with lamp as before)

Occasionally the monitor will function perfectly OK from startup and the images are normal.
My apologies for the quality of the photo.

: Ref from back of LCD unit : LM190E03 (B4) (N9) 6091L-0270A 050216JPP (Phillips component apparently)
: Refs from board and components: Yuyang telecom YP1904L : IT0251 NY0437C

Many thanks in advance.

[PlainBill]

Re: LG Flatron 1915S monitor display fault.

Nice, France. Well, I know at least one person who would be glad to come over and help you - when the weather is warmer.

The symptoms indicate either a problem with the inverter (roughly the upper half of the circuit board you show) or a bad CCFL. Offhand I'd think that the inverter is detecting a fault condition (overload from the CCFLs?) but is not latching in the off state the first time. Or it could be caused by bad caps.

Pictures of the back side of the circuit board would help. Either clear pictures of the electrolytic caps, or the brand name, value, and voltage would also be useful.

PlainBill

[stuart06]

Re: LG Flatron 1915S monitor display fault.

Hello and thank you for your input.
There are worse and better places in the world to be than Nice,France.Unfortunately during the last few years the crime rate has notably increased dramatically and general security standards have declined.As you are probably aware the EEC continues to expand.

Unfortunately the camera I have doesn't give ultra defined photos,not to mention its operator isn't too bright with a camera either so I hope the info and attachments I supply may help a little.

The 25v + the 16v caps are Samxon brand (green colour)
The 50v's are Samxon brand (black colour)

Many thanks in advance for any further support.
Kind regards.
Stuart.

[PlainBill]

Re: LG Flatron 1915S monitor display fault.

None of the caps are visibly bad as far as I can tell. Samxon is regarded as a good brand. Still, even good brands go bad. If these were all Elite brand I'd say go ahead and replace them all, but Samxon??? The one I'd be most suspicious of is the 33uf 50V cap. I believe this is part of the inverter.

I also notice there is some discoloration due to heat from the drive transistors. This doesn't appear to be excessive. Still, it makes me wonder if you aren't dealing with a failing ccfl. Perhaps one of the REAL experts will offer suggestions.

PlainBill

[stuart06]

Re: LG Flatron 1915S monitor display fault.

Hi.
Thank you again for your input.
Would I be correct in assuming the only method of testing for a possibly defective CCFL would be to get hold of another known working lamp and attempt to identify the faulty component by an elimination process of testing/replacing each lamp until the culprit is identified or am I missing something along the line here which is the most probable assumption.
All suggestions and advice are greatly appreciated.
Kind regards.

[Bobdee]

Re: LG Flatron 1915S monitor display fault.

Hello Stuart
Read this link and use 1 to 4 to find out if its your inverter or CCFLs that is responsible for shutdown

https://www.badcaps.net/forum/showpo...&postcount=296

bob

[stuart06]

Re: LG Flatron 1915S monitor display fault.

Hi Bobdee.
Thank you for your reply and please accept my apologies for the delay in replying.
I haven't had much time spare recently to pursue this project lately so unfortunately didn't have the opportunity to check out the procedure listed in the link you supplied,but will get around to it within a few days all being well.
I have managed to get some more defined pics of the board and have posted them on this thread.
Many thanks.
Kind regards.

[bullwinkle]

Re: LG Flatron 1915S monitor display fault.

Hi.
Thank you again for your input.
Would I be correct in assuming the only method of testing for a possibly defective CCFL would be to get hold of another known working lamp and attempt to identify the faulty component by an elimination process of testing/replacing each lamp until the culprit is identified or am I missing something along the line here which is the most probable assumption.
All suggestions and advice are greatly appreciated.
Kind regards.

Yes you can do this kind of process. Remember this is a high voltage area. Be careful.

[bullwinkle]

Re: LG Flatron 1915S monitor display fault.

Check also the power FETs

[liggy]

Re: LG Flatron 1915S monitor display fault.

I have the exact same problem. my ccfl are fine, it is the inverter that I am having issues with. (I spent 80 bucks for the monitor) found a replacement for 50 bucks, but not gonna spend that much, especially if its just a few caps I have to replace. I am not that electronically inclined, but still if I can swap out a few components for about ten bucks as apposed to buy a new inverter board. found universal ones on ebay for about 15 bucks (Dual, so I'd need two). Saw a few conversions on instructables.com from ccfl to LED but not sure I want to do that as the LEDs would not fit on the edge (unless I use the new luxeon leds) Thanks.