Run LCD monitor with 2 CCFL out of 4

[expert_vision]

I have one of those "2 seconds to black" problem, and is because 2 of the 4 CCFL are broken.
The top 2 CCFL still works, and I was wondering, how can I fool the inverter IC that there are 4 lamps?

The model of my power supply used by my monitor (Samsung 940N) is IP-35155A with the schematics attached.

What voltage do I have to apply on pin3 - OLP (Open Lamp Protection) on the SEM2005 IC, to prevent the stopping?

Also, why is there needed a protection for the inverter in case it doesn't have a load?

On the inverter output it says, "650V~/7.5mA". Can't I use only 3mA?

[expert_vision]

Re: Run LCD monitor with 2 CCFL out of 4

"Incorporate open lamp and overload protection in the circuit design. Open
lamp will cause full voltage in the transformer output and will burn the
transformer."

Ok, so I need a different inverter for 2 lamps, R C L load replacement (???), some actual CCFL replacements or replace the whole CCFL with LEDs power from 12V line that goes already in the inverter.

Honestly, this CCFL is a lot of pain. Why was CCFL chosen over LED in LCDs? Is CCFL more reliable than LEDs?

[expert_vision]

Re: Run LCD monitor with 2 CCFL out of 4



Dear lord, I'm actually thinking to convert my CCFL to LED strips. They seems quiet cheap. Bye bye inverter!

[leapius]

Re: Run LCD monitor with 2 CCFL out of 4

I have to agree with you about LED backlight debate. One advantage is better colour reproduction on CCFL. I did read about someone using a resistor in place of a bulb to provide the same load. You'd need to ask someone with more knowledge about specifics.

Simply ripping out your bulbs and inverter and putting in a strip of LEDs can be done but it's not so easy as the a/v board and psu won't like it and will likely just shut off.

[mariushm]

Re: Run LCD monitor with 2 CCFL out of 4

When LCD monitors started to be made, the leds weren't that great.. not so efficient, color accuracy was bad and the white was hard to accomplish (white leds are blue with a layer of phosphorus inside)
Nowadays it's much better.

[expert_vision]

Re: Run LCD monitor with 2 CCFL out of 4

In the end, I bought a broken LCD with good lamps and replaced all 4 of them with practically brand new ones. So anyone out there with bad lamps I suggest you do the same, because if one lamp is out, pretty soon the others will fail too, so replace them all.
Just find a broken LCD of the same size with good lamps. Basically, any LCD that has the same size and nr of lamps as yours, will have lamps that fit, but if you buy the same brand as yours it might make your life a little bit easier. I bought a different brand and I had to remove the lamps out of their housing and put them in the old one, which was a pain because I had to find a substitute for the rubber silicon that held them in place. I used hot glue, having no idea that laps gets so hot that they melt the glue. But is fine, because I also used some cardboard to keep the lamps separated, and the hot glue helps them stay together, even though it's melted.