Samsung 2253LW

[budm]

Re: Samsung 2253LW

If you look at the voltage chart printed on the board, you will notice that the 13V is rated at 0.0A which cannot beright, I do not go by what the print indicates any more.
For example the SAMSING 740N also has rating of 5v and 13V printed, the measured voltage is 15V with the lamps on:
http://s807.photobucket.com/user/bud...ml?sort=3&o=14
http://s807.photobucket.com/user/bud...?sort=3&page=1

[jahjhai]

Re: Samsung 2253LW

i tested the LCD to my surprise the backlight is flickering then disappears i hear like a leaking sound of high voltage... what i did a while ago was resoldering the mosfets and perform some test.. the 13V become 14V.. but still it will not provide any video to the screen... i need to know more about the mosfet cause it think they may be the culprit.. stm8309 i think?? or is it stm 8303??

[selldoor]

Re: Samsung 2253LW

you will have to check as there are both

http://pdf1.alldatasheet.com/datashe...P/STM8303.html

http://pdf1.alldatasheet.com/datashe...P/STM8309.html

i tested the LCD to my surprise the backlight is flickering then disappears i hear like a leaking sound of high voltage

Sounds like ccfl or wiring fault perhaps inpect it. Can you make a test bulb /s from a cfl as in budms signature file

[jahjhai]

Re: Samsung 2253LW

@selldoor..

i manage to test the backlight of the LCD monitor and there is not short circuit.. LCD backlight is all good..

[budm]

Re: Samsung 2253LW

"test the backlight of the LCD monitor and there is not short circuit. LCD backlight is all good." How did you test them? It sounds to me you have high voltage arcing due to bad connection or insulation breadown.

[jahjhai]

Re: Samsung 2253LW

OK so here's what i did.. first of i have this http://www.goodluckbuy.com/images/de...ku_73585_2.jpg,

i have to use this link instead..

anyway yes the LCD backlight is indeed working good using the supply of that light that i used to test.

In my experiment i also used the ccfl lights and use it in the board and what i found out is, it lights up then turn off... i dont know whats wrong with it this time. could it be theres another component that is faulty? all electrolytic caps are already replaced except the big one.

and another observation is that when i use the main backlight of the LCD i noticed sparking kind of thing like a short circuit... probably a bad connection i rather have to caulk it or use glue to fix it.. anyhow the LCD backlight is proven to be in good condition so we have to focus on the board..

again by using the ccfl that i use to test it turns on for a sec then off.. then nothing happens..

hope this explains everything so that we can go directly to the faulty component.. hoping we can resolve this soon..

thanks so much guys for being specially budm happy new year.............

[selldoor]

Re: Samsung 2253LW

anyway yes the LCD backlight is indeed working good using the supply of that light that i used to test.

and another observation is that when i use the main backlight of the LCD i noticed sparking kind of thing like a short circuit... probably a bad connection i rather have to caulk it or use glue to fix it.. anyhow the LCD backlight is proven to be in good condition so we have to focus on the board..

again by using the ccfl that i use to test it turns on for a sec then off.. then nothing happens..

The back lights were NOT good and even though you have glued/caulked them they may still not be good when they get hot.

Anyway it appears you have multiple problems - have you been able to decide if it is stm 8303 or 8309

Next thing to check is to locate the Inverter transformers and test the secondary windings. No power to board meter on ohms 2000 Test S1 to S2 and S3 to S4 on attached

[jahjhai]

Re: Samsung 2253LW

Next thing to check is to locate the Inverter transformers and test the secondary windings. No power to board meter on ohms 2000 Test S1 to S2 and S3 to S4 on attached

about the stm8303 and 8309 i may have my fear of not having them purchased locally here in the Philippines. What i need to know is how to ensure that these stm8303/stm8309 are working good. i don't know how to test them using the digital multimeter.

Sorry about that..

thanks to the picture but i dont know how if im going to use the digital multimeter.. i need help on that one.

thank you, looking forward for another result...

oh by the way what happened to my LCD monitor was it was attacked by red ants where they used it as their nest and probably shorted some internal circuits. that is why i have multiple problems with it.

[selldoor]

Re: Samsung 2253LW

Please tell us the model of your multimeter

[lexwalker]

Re: Samsung 2253LW

OK so here's what i did.. first of i have this http://www.goodluckbuy.com/images/de...ku_73585_2.jpg,

i have to use this link instead..

anyway yes the LCD backlight is indeed working good using the supply of that light that i used to test.

In my experiment i also used the ccfl lights and use it in the board and what i found out is, it lights up then turn off... i dont know whats wrong with it this time. could it be theres another component that is faulty? all electrolytic caps are already replaced except the big one.

That bolded part sounds like the 2 seconds to black syndrome...

and another observation is that when i use the main backlight of the LCD i noticed sparking kind of thing like a short circuit... probably a bad connection i rather have to caulk it or use glue to fix it.. anyhow the LCD backlight is proven to be in good condition so we have to focus on the board..

again by using the ccfl that i use to test it turns on for a sec then off.. then nothing happens..

hope this explains everything so that we can go directly to the faulty component.. hoping we can resolve this soon..

Which section is that? Is it the connection at the CCFL tubes inside the panel, or at the connectors (when connected to the board), or on the circuit board itself?

[jahjhai]

Re: Samsung 2253LW

im using a sanwa rd701

heres a reference pic

http://www.e-v-t.ru/imgbig/sanwa/pc520m/pc520m_1433.jpg

my doubt now is the stm8303 or stm 8309 unfortunately i don't know were to purchase these online..

@lexwalker yeah it does that black syndrome..

i saw the sparks in the connectors.. selldoor is right even if i did put some glue it can still damage the poor insulated areas but why is it if i use a different inverter the backlights are good?

thanks for sharing me your ideas and knowledge about it.. looking forward for new discoveries..

[BigDaddyAdy]

Re: Samsung 2253LW

Hello, jahjhai, have you managed to find out the problem?
those mosfets are 8309 not 8303.
I have the same board, same problem.
I replaced caps, mosfets and now backlight comes on for 2 sec, then only image, no backlight.
I found one smd resistor, and one smd cap which look burnt. Those are for OVP circuit for SEM2000. I found a schematic for sem2000 usual setup and it looks pretty much like the one on board, but there are no values there.
Anyway, i measured the voltage on OVP pin for sem2000 and it rises to 5V. In the datasheet says that this value should be around 2V.

Can you tell me from your board what values are written on the resistors. I have attached a picture here:
https://www.badcaps.net/forum/showpo...8&postcount=59
The culprits are marked with red.
What i did is i removed the resistor which looks damaged from the board and the problem is the same, 2 sec backlight, now the voltage on OVP pin on sem2000 is around 5V from the begining, it's not rising anymore.

[budm]

Re: Samsung 2253LW

Do you have the link to that SEM2000 so I can download the spec?

[selldoor]

Re: Samsung 2253LW

What i need to know is how to ensure that these stm8303/stm8309 are working good. i don't know how to test them using the digital multimeter.

Sorry about that..

thanks to the picture but i dont know how if im going to use the digital multimeter.. i need help on that one.

You can buy them on ebay - will ship to Philippines

To test see this thread
https://www.badcaps.net/forum/showthread.php?t=25926

Meter instruction see attached picture
For Resistance and Diode tests No POWER TO SET

[BigDaddyAdy]

Re: Samsung 2253LW

Here is the datasheet of SEM2006.
It is 2006, not 2000 as i stated in my previous posts.

https://cdn.badcaps-static.com/pdfs/...4772d38b5d.pdf

[budm]

Re: Samsung 2253LW

OK, that is why I cannot find the spec. I would check the DET pin which is for Open lamp/lamp will not fire up, if the lamp has open wire, I would expect voltages at DET and OVP to go above normal.

[BigDaddyAdy]

Re: Samsung 2253LW

I tested the lamps with another inverter and tested OK.
I am still waiting for those values to replace those parts and continue testing.

[lexwalker]

Re: Samsung 2253LW

@lexwalker yeah it does that black syndrome..

i saw the sparks in the connectors.. selldoor is right even if i did put some glue it can still damage the poor insulated areas but why is it if i use a different inverter the backlights are good?

Are those connectors with the sparks flying on the power supply board side? Are there any capacitors between the connectors and the inverter transformer (usually ceramic disc type with values around 33pF to 15pF depending on inverter design)?

[jahjhai]

Re: Samsung 2253LW

Are those connectors with the sparks flying on the power supply board side? Are there any capacitors between the connectors and the inverter transformer (usually ceramic disc type with values around 33pF to 15pF depending on inverter design)?

here's the picture i have for my board. https://www.badcaps.net/forum/attach...2&d=1388113697

the blue ceramic caps i believe has labels of 3kV??? no sparks flying on the board side.

[BigDaddyAdy]

Re: Samsung 2253LW

@jahjhai Do you think you can give me the values for those components?

https://www.badcaps.net/forum/attach...7&d=1389131446