Samsung 2494SW won't turn on...

[micromirko]

Hi there!

I have a problem with my Samsung 2494SW which i bought dead already. Before I successfully repaired a Samsung Syncmaster 2333SW by just changing all Low Esr Caps. So i decided to buy another broken one.

I changed all Caps on this one but it still doesn't work. I searched the net - that's how i found this Forum - and it looks like the next most likely path leads to the inverter.

I already checked the hight voltage output on this board - there is no one - i guess because it is in standby mode when attached to power only without connection to the control panel.

Any suggestions were and how to check next?

See Photos attached.

[Rtech]

Re: Samsung 2494SW won't turn on...

The photos in line are not helping. Please use GO advanced and Manage attachments.
The symptoms are rather vague !!.Does the Power Light come on ??/ does it change colour when a signal is applied ??Do you mean by 'no high ' voltage that all is ok except the inverter side ???

[micromirko]

Re: Samsung 2494SW won't turn on...

Da ich anscheinend meinen Thread nicht editieren kann hier die eingebetteten Bilder.
Sorry - should write in english...
It looks like there is no way to edit my first post so i use the reply function.
All other answers to follow...

[micromirko]

Re: Samsung 2494SW won't turn on...

Ok, i finally found the time to check.

When i switch on the Monitor it shows me the Windows Desktop for about 2 seconds then it goes black. The Power LED stays Blue, it doesnt change when a signal is applied. When tab on the Monitor without a signal attached the backlight switches on for about 2 seconds then it goes black.

Q: Do you mean by 'no high ' voltage that all is ok except the inverter side ???
A: No, i tried to measure the 800V on the inverter output but couldnt - guess because there was no control panel attached that time.

I start searching for the 2 seconds black phenomena.......

[micromirko]

Re: Samsung 2494SW won't turn on...

In another thread retiredcaps asked to check the inverters.

https://www.badcaps.net/forum/showth...ight=2+seconds

I checked mine with my multimeter (set to 2M Ohms) and the readings are:

0.220 between the red circles and 0.222 between the yellow circles

when i compare this to the answers in the other thread i guess my inverter is ok.


...... searching goes on......

I also ohmed the 4 very small blue ballast caps for the lamps - i couldnt measure any reading on my multimeter even when set to the highest possible 20 M Ohms. Thats what a capacitor should show so i guess these are ok also...



....... searching goes on ......

[Rtech]

Re: Samsung 2494SW won't turn on...

You need to check the Lamps themselves,and ensure a BL On signal is being sent from the Logic Board..this should be marked on you PSU board.

[micromirko]

Re: Samsung 2494SW won't turn on...

tried do check with only one of the 4 ccfl's attached (tested all 4 separately) - no lights at all. How can i check if one of the ccfl's is bad? Do all lights have to be attached and be ok so the powersupply works? That means if one of them is bad all bulbs wouldnt light up? That means its not possible to attach the ccfl's one by one to find out whitch is bad? Then there must be another way to test the ccfl's

....... searching goes on ......

[micromirko]

Re: Samsung 2494SW won't turn on...

You need to check the Lamps themselves,and ensure a BL On signal is being sent from the Logic Board..this should be marked on you PSU board.

dont know how to check the lamps themselves... will find out somehow.

dont know how to ensure a BL On signal is being sent from the Logic Board. I do read on one connector:

GND
Key2
Key1
LED
3.3v

and on the other:

B-Dim
+15V
GND
GND
+5.1V
+5.1V
DCR
ON/OFF
+3.3V
LED
KEY1
KEY2

Checked the Schematics of the Inverter IC BD9293F - couldnt find any readings like "Backlight on" - Signal on Pin...

....... searching goes on ......

[micromirko]

Re: Samsung 2494SW won't turn on...

ok on another thread i read:

You have to have 4 working lamps, if one failed or not connected, the inverter will go onto shutdown mode.

so one question is answered

[micromirko]

Re: Samsung 2494SW won't turn on...

thinking about replacing ccfl tubes with led stripes.............

[micromirko]

Re: Samsung 2494SW won't turn on...

So without even being able to test it (you know how ? please let me know) i guess that at least one of the ccfl's are bad (non working or consuming too much power cause of age).

and even without checking i guess that buying 4 new ones will be not worth it. still thinking about a led replacement. You read about someone in the www who successfully did it? Please let me know.

[selldoor]

Re: Samsung 2494SW won't turn on...

You can buy a bulb tester on ebay or from lcdparts.net
What else you can do is to make a test bulb (two is better) see here

https://www.badcaps.net/forum/showth...er+testing+cfl

You then sub these for the proper bulbs and eliminate the bad ones

[micromirko]

Re: Samsung 2494SW won't turn on...

You can buy a bulb tester on ebay or from lcdparts.net
What else you can do is to make a test bulb (two is better) see here

https://www.badcaps.net/forum/showth...er+testing+cfl

You then sub these for the proper bulbs and eliminate the bad ones

I saw this thread already - going to build one asap.

Still think about how long until the next bulb leads to dark screen cause when i change one bulb the others are still old. Any experiences changing from ccfl to led?