14" "TWIX" TFT LCD monitor

[tmcw]

Picked up this monitor last week, non-working. Date stamps show it was made around 2004.

There is a picture on-screen, I can see the desktop in very good light, but the backlight isn't coming on. It uses an external power supply (like laptop power brick), which is outputting the correct 12V.

Inside the case, the parts look like they would be used in laptops. Certainly, a search of the Samsung panel on google shows that it's been used in Dell laptops of that era (panel).

The inverter is an Emax PLCD2215202E, looks like it's been used in laptops as well. The connection from the mainboard to the inverter consists of 4 wires, on the red and black wires I'm seeing 5V and 12V, the other 2 wires up to 50mV, so presume these are signal wires, and the 5V and 12V are good.

I've uploaded a couple of pictures of the inverter board. The 2A fuse is ok. Are the 3 caps likely candidates for replacement here? The panel doesn't light up for an instant, so wondering if I should be looking at the panel/CCFLs for problems, or anything else I should rule out first?

[Rtech]

Re: 14" "TWIX" TFT LCD monitor

The other wires, should be Dim and also a Dc voltage to turn the inverter on.So with the monitor switched on and a signal put on it, you should be able to measure the 'On' voltage to the Inverter.

[tmcw]

Re: 14" "TWIX" TFT LCD monitor

Yes, you're right, I had another look at the wires going to the inverter, and I made an error in my first post. This is how they actually are...

The 4 wires from the mainboard to the inverter are as follows:

Red - always 12.07V
Black - ground
Brown - always 4.87V
Green - 50mV when monitor is off / 5.00V when monitor is switched on

Do they sound like they're behaving correctly?

I tried switching the monitor on and off in the dark, and there is the vaguest of flickers of light off the panel, just a flash before it goes out, but the panel always has the video.

There's also a bit of a sizzle of the inverter for the brief time the CCFL seems to be trying to come on and a video signal. It doesn't seem to sizzle when there is no video signal, and the green wire isn't fired up.

[Rtech]

Re: 14" "TWIX" TFT LCD monitor

Well apart from reflowing the solder on the transformer pins,the other option is to plug in a spare ccfl into the lamp socket, and see if that works.

[tmcw]

Re: 14" "TWIX" TFT LCD monitor

Thanks for the pointers.

It didn't really occur to me to plug in another CCFL (still learning), and although I didn't have one spare, I do have a 15" panel, so I opened that up, connected up it's CCFL to the inverter, and it worked! Everything seemed to be working as expected, coming on when a VGA signal present, switching off when no signal, or PC goes into power saving mode, so it seems the electronics are ok.

Went ahead and opened the panel, and the CCFL looked very black both ends, and one end (the pink end) broke under the slightest of stress, so it looks like it's just the CCFL that's the problem here.

Next question is how do I go about getting a replacement CCFL? There are no markings, the tube is about 28cm in length. Is there some one-stop shop that I can browse and pick what I need?

[jetadm123]

Re: 14" "TWIX" TFT LCD monitor

Thanks for the pointers.


Next question is how do I go about getting a replacement CCFL? There are no markings, the tube is about 28cm in length. Is there some one-stop shop that I can browse and pick what I need?

You can try ccflwarehouse.com. They have a written guide to help you properly measure the ccfl. However, since it's a 14" monitor, it may not be worth fixing due to the high price for replacement ccfl's.

[tmcw]

Re: 14" "TWIX" TFT LCD monitor

Thanks for the link.

I found the CCFL for the Samsung panel easily enough there, $15 for CCFL, caps, leads and connector, plus shipping to Ireland probably wouldn't make it an economical repair.

Think I'll box it up and shelve it for now, might be lucky enough to pick up a broken laptop with a good CCFL in it later on. At least I learned a little more from the exercise.

Thanks again.