LG Flatron W1934S, 2 sec to black issue

[senndogg]

Hello to everybody and welcome to my first post. i am an electronics amateur and i find this forum very useful, used it very often, like an unknown user, but today i have to post my problem.
i used the search button regarding my topic but nothing relevant came.
i followed the "2 sec to black" bible, but im a bit stuck.
the monitor is a LG 19" wide. the backlight goes off after 2 secs. it is reccaped, tried new ccfl but the problem persists. i followed also the pdf service manual but im stuck at the "instantaneously pulse wave on pin1, pin3, pin15 of IC501 at the moment of restart". i get 5Volts and 14.7 volts at most of the power caps.
thank you.

[alexanna]

Re: LG Flatron W1934S, 2 sec to black issue

When you substituted CCFLs,
Were you able to use 2 known good bulbs? And did you have all the connectors on the inverter populated with a CCFL?

[senndogg]

Re: LG Flatron W1934S, 2 sec to black issue

yes. it was taken from a working Samsung. just the same problem. but i used only one bulb.

[alexanna]

Re: LG Flatron W1934S, 2 sec to black issue

I possible try to use 2 known good CCFs.
It is possible to have more than one bad CCFL

[senndogg]

Re: LG Flatron W1934S, 2 sec to black issue

when i made the test i disconnected the two CCFLs and tested the two inverters with the known good working samsung ccfl.
thanks for the reply but i dont have many monitor related gadgets in my small garage. i can put my hands on my own green ccfl pc case light decoration, but it has other kinds of connectors.

[senndogg]

Re: LG Flatron W1934S, 2 sec to black issue

after doing some searches in this forum, i must question: if the hot circuit is open, the transformer senses a fault and shuts off, right? so if the CCFL is faulty or improper the "2sec to black" will still occur?

[selldoor]

Re: LG Flatron W1934S, 2 sec to black issue

Hi did you search "W1934S" there are other members who have had similar problems with this monitor?

[alexanna]

Re: LG Flatron W1934S, 2 sec to black issue

after doing some searches in this forum, i must question: if the hot circuit is open, the transformer senses a fault and shuts off, right? so if the CCFL is faulty or improper the "2sec to black" will still occur?

Yes.



On the great majority of monitors, if the inverter detects an open circuit or notices excessive voltage the inverter circuit will shut down to try to prevent damage. That is what we call 2 second to black.So one or more missing CCFLs can cause the inverter to shut down.
There are many things that can cause a 2 second to black problem.
Some of the common ones,
Bad capacitors
Inverter transformer resistance problem
CCFLs and are their wiring.

[senndogg]

Re: LG Flatron W1934S, 2 sec to black issue

thank you, today i will try 2 original brand new CCFLs. i suspect that the upper one has defective wiring.

[senndogg]

Re: LG Flatron W1934S, 2 sec to black issue

thanx to everyone, specially to alexanna and selldoor, for this fantastic forum.
my problem is resolved, a wiring failure in the upper CCFL



By senndogg at 2011-12-27


By senndogg at 2011-12-27


i changed the wiring, soldered it, plugged and everything OK!



By senndogg at 2011-12-27


thank you guys! you're awesome!

[zeusbv]

Re: LG Flatron W1934S, 2 sec to black issue

Yes.



On the great majority of monitors, if the inverter detects an open circuit or notices excessive voltage the inverter circuit will shut down to try to prevent damage. That is what we call 2 second to black.So one or more missing CCFLs can cause the inverter to shut down.
There are many things that can cause a 2 second to black problem.
Some of the common ones,
Bad capacitors
Inverter transformer resistance problem
CCFLs and are their wiring.

i have the same problem but the display and ccfl are on for 2 sec then the ccfl are of and the lcd remains on
can I measure the ccfl ?

[alexanna]

Re: LG Flatron W1934S, 2 sec to black issue

i have the same problem but the display and ccfl are on for 2 sec then the ccfl are of and the lcd remains on
can I measure the ccfl ?

On some it is possible to measure the return lines, and if a bad CCFL is present a difference in voltage can sometimes be noticed.
However I am not willing, or unable to go into that at the moment.
I recently fractured a vertebra in my lower back, so I a am about worthless as ---- on a boar hog!
If the capacitors do not show any bulging, and are not on the problem [Replace on sight list].
And you have verified that the secondary windings in the inverter coils are within the 3% range. It's time to either substituting known good CCFLs, are open up the LCD for a visual on the bulbs.

[senndogg]

Re: LG Flatron W1934S, 2 sec to black issue

On some it is possible to measure the return lines, and if a bad CCFL is present a difference in voltage can sometimes be noticed.
However I am not willing, or unable to go into that at the moment.
I recently fractured a vertebra in my lower back, so I a am about worthless as ---- on a boar hog!
If the capacitors do not show any bulging, and are not on the problem [Replace on sight list].
And you have verified that the secondary windings in the inverter coils are within the 3% range. It's time to either substituting known good CCFLs, are open up the LCD for a visual on the bulbs.

i wish you get well soon alexanna.

[Behemot]

Re: LG Flatron W1934S, 2 sec to black issue

This stinks guys. Got exactly the same 2 secs, changed first transformer, changed second transformer, still the same problem. ATM running with CCFLs from 22'' display just fien so the problem is here. Very interesting is that I now got 8 transformers, several of them with resistance around 615 ohm, several around 930 and some around 940 ohm…WTF? do doubts it goes bad with „tollerances“ like this…you have to manualy pick up the closest ones.

Anyway, it is way too suspicious that two different monitors show the same CCFL soldering problem. Some planned obsolescence? Or Inolux has SO bad manufacturing quality?

ADD// yes, it was bad joint, there was some discharge between the wire and the CCFL going on