Samsung 2253bw black screen

[BigDaddyAdy]

Re: Samsung 2253bw black screen

Yes, the image is there, only the invertor is not working.

[selldoor]

Re: Samsung 2253bw black screen

Does your board have the small green torpedo fuse is it good and what is the voltage on it relative to a ground screw.

What are the part numbers of the inverter transformers - have you tested them?

[budm]

Re: Samsung 2253bw black screen

Is the BL_ON (ON/OFF) signal still present when the backlights go out?
12-PIN connector
1- b-dim
2- 13v
3- gnd
4- gnd
5- 5.1v
6- 5.1v
7- a-dim
8- on/off
9- 3.3v
10- led
11- key 1
12- key 2

[BigDaddyAdy]

Re: Samsung 2253bw black screen

The fuse is good, the voltage is 13.6V.
The Bl_On Goes to 4.5V if i remember correctly, i will have to check again in the morning.

[budm]

Re: Samsung 2253bw black screen

If I were you, I will use two test lamps to verify if it is the board problem or the lamps problem. Can we see the top side of the board to see if the ballast caps look OK or not, also you should check the high voltage winding of both inverter transformers.
https://www.badcaps.net/forum/showthread.php?t=19987

[BigDaddyAdy]

Re: Samsung 2253bw black screen

The lamps are ok.
As i told you, there is a problem with OVP (over voltage protection) circuit. One smd resistor and one smd capacitor look damaged and i can't identify their values. Could anyone give me their values or give me a schematic so i can change them?

[budm]

Re: Samsung 2253bw black screen

If you can get the P/N of that PWM IC, then you may be able to tell what the function of that resistor and the cap are for.

[budm]

Re: Samsung 2253bw black screen

You can contact the jahjhai of this thread also.
https://www.badcaps.net/forum/showthread.php?t=20459

[domy_os]

Re: Samsung 2253bw black screen

Hi,

I have faulty 2233BW monitor and would like to repair the PSU board rather then buy the new one. Capacitors looks good but I changed them with low ESR models and problem is still here. After switching monitor on, CCFL works for about few seconds, then turns off. I can see the picture with flashlight and I hear some squeaking from board. I did some readings while monitor was turned on:

Resistance on inverter secondary trafo: around 1100 Ohm
Voltage on inverter primary trafo: 0 V
Resistance between MOSFET pins: I could't measure it with my meter, scale was on 2 MOhm and it showed up just number 1
Voltage between F301 fuse and ground: around 14.6 V

I have only basic experience with servicing electronics. Can you help me? What's wrong with PSU board? Thank you.

[budm]

Re: Samsung 2253bw black screen

https://www.badcaps.net/forum/showthread.php?t=19987
I would test the board with two test lamps to eliminate the possibility that you may have bad lamp/lamps, or bad wiring on the lamps.

[selldoor]

Re: Samsung 2253bw black screen

Hi,

Resistance on inverter secondary trafo: around 1100 Ohm

You should have two reading and they need to be exact - not "around"

[domy_os]

Re: Samsung 2253bw black screen

I use LED and tungsten bulbs in my apartment so I don't have such lamps but will try to find it somewhere.

What can I do next until I get some CFL lamp?

[domy_os]

Re: Samsung 2253bw black screen

Sorry, I can't edit above post.

You should have two reading and they need to be exact - not "around"

Resistance on first trafo: 1060 Ohm
Resistance on second trafo: 1111 Ohm

[selldoor]

Re: Samsung 2253bw black screen

That looks like your problem- they should be within 3% - what is the number on the
transformer/s

[domy_os]

Re: Samsung 2253bw black screen

TM-21240. I made a few pictures with old caps...

EDIT: Deleted Dropbox link and photos uploaded as attachment.

[selldoor]

Re: Samsung 2253bw black screen

Please can you repost the pictures using manage attachments so they
remain with the thread to help others.

[domy_os]

Re: Samsung 2253bw black screen

So, I have to replace inverter trafos? I found one on eBay but it's too expensive. The new PSU board costs less then one pair of trafos. Is there any alternative part number?

[selldoor]

Re: Samsung 2253bw black screen

I dont think there will be an alternative - perhaps wait and see if any more
input and if you can get a cfl bulb for budm's tester. It could be that on a high resistance one the 3% can stretch to 5% . I cant find what it should be but I note on lcdparts.net at the top of the inverter section it says 10%!! which is a bit freaky as we have fixed many sets that have been just over 3% by advisng to change the transformer.

EDIT perhaps message the ebay seller and ask if they can tell you the value of the secondary
resistance.

[ilsinho]

Re: Samsung 2253bw black screen

Secondary resistence should be around 1380 ohm.

[Rtech]

Re: Samsung 2253bw black screen

My experience with Inverter transformers,is that the 3% supposed error limit is certainly not sacrsanct !! I have seen many with more than 5% which were not faulty,and others approaching the 10% also.However Samsung ones do seem to fail at the lower levels,for whatever reason,and in various of their Models it is a standard fault...is this one of the Monitors that has the latter ??