Help on Samsung Syncmaster T220 dead ccfl lamp

[mikey5791]

Hi,

This monitor previously is my main working monitor which i have been using for 8~9 years. Yesterday, when i switched on my pc from fresh to power on, the monitor is just black no display. I started dismantle to look inside the monitor power board but nothing looks suspicious or burnt. So i took my external ccfl inverter to try to power the monitor ccfl lamps which consisted of 2 lamps on upper part and 2 lamps on the lower part.

Found out the upper ccfl lamp which is supposed to connect to cn304 on the power board did not light up. Then i installed a used working ccfl lamp on cn304 lamp connector. Now the monitor is back to working condition with the used working ccfl lamp still hanging outside the power board as i have not opened the delicate lcd panel yet. I am afraid i might damage the other upper working ccfl lamp.

My question here is why the monitor can't display when there is only 3 working ccfl lamps (1 ccfl lamp is tested burned)? Is there any hack that we can do to sort of cheat the monitor to use only 3 ccfl lamps instead of the normal 4 lamps. I am attaching picture of the power board and the monitor working after i temporary attached a good ccfl lamp on cn304 lamp connector.
Any help and kind comments will be much appreciated.

[stj]

Re: Help on Samsung Syncmaster T220 dead ccfl lamp

the invertor monitors the current, 3 lamps uses less than 4 so it detects a fault.

there is a fair chance that the lamp is still useable and the wire has broken or burned off one of the pins btw.
because usually the lamps all start to fail around the same time.

[momaka]

Re: Help on Samsung Syncmaster T220 dead ccfl lamp

[QUOTE=mikey5791;996031]Found out the upper ccfl lamp which is supposed to connect to cn304 on the power board did not light up. Then i installed a used working ccfl lamp on cn304 lamp connector. Now the monitor is back to working condition with the used working ccfl lamp still hanging outside the power board as i have not opened the delicate lcd panel yet. I am afraid i might damage the other upper working ccfl lamp.[/quove]
I've had to do that before - replace one lamp in a set of two. It was a bit delicate, but not that bad really. In all honesty, that was probably the easier part. The harder part was taking out the panel with the attached t-con board and making sure I don't damage any of the ribbons. On top of that, keeping the diffuser sheets clean and free or lint and dust can get difficult (though I imagine you have fairly warm and humid climate in Malaysia, so particulate dust should be low.)

My question here is why the monitor can't display when there is only 3 working ccfl lamps (1 ccfl lamp is tested burned)?

As stj said, inverter is designed to detect faulty CCFLs and shut down.

Is there any hack that we can do to sort of cheat the monitor to use only 3 ccfl lamps instead of the normal 4 lamps.

Maybe. Maybe not.

I've done it on an old Dell E193FPc monitor that kept blowing BJTs on the lower inverter. I couldn't figure it out, so I disabled the entire bottom inverter by moving around a few resistors / jumpers and setting the driver IC feedback to not care about monitoring the lower inverter. With that said, depending on what driver IC your monitor has, this may be a fairly easy task or may be pretty complicated.

Also, worth mentioning is that when I disabled my lower inverter (both bottom CCFLs) the monitor's contrast on the bottom was quite poor. It was still perfectly readable for text. But for image editing, it was quite terrible. So keep that in mind if you do decided you want to disable the inverter with the problematic CCFL on yours. And note I said disabled the entire inverter. You cannot disable just one CCFL.

Another rather cumbersome and probably not so-good-idea of an alternative would be to cobble together a resistor network that draws as much current as the bad CCFL and just connect that to the inverter. However, I'm not quite sure if this would work (in theory, it should.) Moreover, each CCFL typically dissipates at least several Watts of power. So whatever resistor network you come up with will have to be able to 1) handle the high voltage from the inverter, 2) handle several watts of heat and 3) keep it well-isolated from short-circuiting to the monitor or a ground (can be challenging unless placed externally somewhere.

So with that said, I think it's better to just replace the faulty CCFL.
Either that, or grab an LED conversion kit and try that out.

there is a fair chance that the lamp is still useable and the wire has broken or burned off one of the pins btw.
because usually the lamps all start to fail around the same time.

Yes, that's possible too. Though I've seen a good number of times too where the tube just failed (cracked around one end where the cathode enters.)

So it is indeed worth for the O/P to investigate on that before getting a replacement tube or converting to an LED kit.

[stj]

Re: Help on Samsung Syncmaster T220 dead ccfl lamp

given the age of the tubes, i would use an led kit if your going to open it.

[mikey5791]

Re: Help on Samsung Syncmaster T220 dead ccfl lamp

Hi stj and momaka,

Thanks for your comments.
Considering the manufacturing year of 2009 , i think the ccfl lamps may soon be going bad.
Also, the upper right hand side of the monitor displays a few vertical lines which i think is not repairable. Those are the two reason i decided to temporarily connect a working ccfl lamp to the power board metal case instead of opening the lcd panel. My lazy mod as long as i can use it for my daily work of typing text at home until it fails again.
Your input and generous suggestion are greatly appreciated.

[stj]

Re: Help on Samsung Syncmaster T220 dead ccfl lamp

those lines are typical samsung!
for some reason the tabs going onto the glass fail a lot more on samsung panels than others.

[momaka]

Re: Help on Samsung Syncmaster T220 dead ccfl lamp

Those are the two reason i decided to temporarily connect a working ccfl lamp to the power board metal case instead of opening the lcd panel. My lazy mod as long as i can use it for my daily work of typing text at home until it fails again.

I like it.
Simple / "lazy" fixes like this are sometimes quite alright. Most likely the monitor will probably work OK for a decent amount of time, if not until it is no longer useful anyways.

those lines are typical samsung!
for some reason the tabs going onto the glass fail a lot more on samsung panels than others.

That's a shame, because I find that Samsung and LG panels usually tend to be a lot better than the others, picture-wise.