Samsung Syncmaster 245BW

[JeremyR]

I saw the recent thread with the same title as mine, but in viewing his pictures it is obvious that our power boards are different. My problem monitor is monitor #2 in a dual monitor setup. With everything plugged in and powered on, if I switch from single to dual monitor setup in Windows, my problem monitor shows the windows background for just a second and then the screen goes black. I've seen other people having this issue and it seems that they always complain about bad caps.

I've taken my monitor apart and looked at my power board, but don't see any 'bulging' caps. There is one cap that has a black mark on the top and it looked very much like just a marker of some kind (I thought it might just be a manufacturing mark). I scratched it and scraped off I also rubbed my finger across it appears to have smeared which leads me to believe it is some sort of capacitor goo. I am a noob's noob with this stuff, but the thought of a cheap resolution to this issue has me very willing to give cap replacement a try.

What I need to know is how to identify the part numbers so I can order them. I am hoping someone can look at my attached pictures and give me some advice.
If it helps:
- the board part# is BN44-00195A (it got cut off a bit on the picture).
- the cap in question is marked as: CB853
- two other caps near it: CB855 and CB857


Thanks,
Jeremy

[PlainBill]

Re: Samsung Syncmaster 245BW

I saw the recent thread with the same title as mine, but in viewing his pictures it is obvious that our power boards are different. My problem monitor is monitor #2 in a dual monitor setup. With everything plugged in and powered on, if I switch from single to dual monitor setup in Windows, my problem monitor shows the windows background for just a second and then the screen goes black. I've seen other people having this issue and it seems that they always complain about bad caps.

I've taken my monitor apart and looked at my power board, but don't see any 'bulging' caps. There is one cap that has a black mark on the top and it looked very much like just a marker of some kind (I thought it might just be a manufacturing mark). I scratched it and scraped off I also rubbed my finger across it appears to have smeared which leads me to believe it is some sort of capacitor goo. I am a noob's noob with this stuff, but the thought of a cheap resolution to this issue has me very willing to give cap replacement a try.

What I need to know is how to identify the part numbers so I can order them. I am hoping someone can look at my attached pictures and give me some advice.
If it helps:
- the board part# is BN44-00195A (it got cut off a bit on the picture).
- the cap in question is marked as: CB853
- two other caps near it: CB855 and CB857


Thanks,
Jeremy

Interesting. That mark IS from a marker or crayon of some sort. However, it appears there may be a slight bulging of the cap. Ir this might be the result of the angle at which the picture was taken.

You are taking the difficult approach to identifying proper replacements. An easier method is to list the characteristics of the capacitors, then order equivalent replacements. This particular is a 2200uF, 10 Volt 105 °C capacitor. It says so, right on the side. Because of it's application, it is also a low ESR capacitor. A suitable replacement would be a Panasonic EEU-FM1A222; Digikey part number P12357-ND.

Now, while Samwah caps are generally good, they ARE known to produce bad lots (production runs). In this case I would suggest doing a few tests before replacing all the caps, or even just this one.

The problem you describe is known as the 'two seconds to black' problem, and can have many causes. Bad caps in the power supply are one of the possible causes (although this cap is not a likely cause), as are bad CCFLs, bad wiring to the CCFLs, a shorted or open inverter transformer, a bad driver to an inverter transformer, or a bad component in the circuitry that monitors the CCFL status.

While you can replace the caps if you want to, I would suggest preforming a few tests first. The first step would be to post pictures of the inverter.

PlainBill

[MDOC]

Re: Samsung Syncmaster 245BW

Interesting that this diode (red arrow) is suspended like a bridge

[JeremyR]

Re: Samsung Syncmaster 245BW

Interesting. That mark IS from a marker or crayon of some sort. However, it appears there may be a slight bulging of the cap. Ir this might be the result of the angle at which the picture was taken.

I think it is just the angle of the picture... it looks pretty flat to me. So that smearing is normal from a marker/crayon? I would think it would have dried out by now.

While you can replace the caps if you want to, I would suggest preforming a few tests first. The first step would be to post pictures of the inverter.

I've attached some more pictures. The 2 caps on this board also look good. Not sure what else you can make of it.

Thanks for the responses and the help!

[PlainBill]

Re: Samsung Syncmaster 245BW

I think it is just the angle of the picture... it looks pretty flat to me. So that smearing is normal from a marker/crayon? I would think it would have dried out by now.


I've attached some more pictures. The 2 caps on this board also look good. Not sure what else you can make of it.

Thanks for the responses and the help!

Quite a bit, actually.

Lecture time: The logic board controls the inverter. When it turns the backlight on, the inverter controller initially turns the backlights on at full brightness. After a few seconds it reduces the brightness and begins monitoring several parameters for each CCFL. These are the current through each CCFL, and the voltage across each CCFL. Possible error conditions are output voltage too low or too high, current too low or too high. Common failures include an aging CCFL drawing too much current, a broken CCFL or wire allowing the voltage to go too high, a shorted transformer causing the output voltage to drop, etc. By comparing these parameters we can often identify the cause of the problem, and fix it.

The next step in this case is to take a picture of the back side of the inverter. I will try to identify points to measure.

PlainBill

[JeremyR]

Re: Samsung Syncmaster 245BW

The next step in this case is to take a picture of the back side of the inverter. I will try to identify points to measure.

PlainBill

There is nothing on the backside...everything is on the front side. If you need me to take some closer pictures, let me know.

[Wrog]

Re: Samsung Syncmaster 245BW

There is nothing on the backside...everything is on the front side. If you need me to take some closer pictures, let me know.

He wants pictures of the backside so that he can see where the traces lead (how the circuits are constructed) and identify test points to take measurements, and not necessarily to see what components are there.

[JeremyR]

Re: Samsung Syncmaster 245BW

He wants pictures of the backside so that he can see where the traces lead (how the circuits are constructed) and identify test points to take measurements, and not necessarily to see what components are there.

Just so there's no confusion, I've attached a picture of the back. There is no circuitry or traces on the back...all the circuitry is on the front side.

Jeremy

[PlainBill]

Re: Samsung Syncmaster 245BW

Just so there's no confusion, I've attached a picture of the back. There is no circuitry or traces on the back...all the circuitry is on the front side.

Jeremy

Aww, that sucks. Let's see if I can figure out something from the front side. For what it's worth, this inverter has an unusual design.

I've marked up the picture. Let's see if I understand a few things about it.

Let's start with the transformer on the left. I've marked the lower pins A B C D. I've marked two upper pins AB and CD. I've also marked the CCFL connectors pins A1 B1 C1 D1.

First set of questions:
Does A connect to A1, B to B1, etc?
Is the small circle between A and A1 actually the circuit trace connecting A to A1?
What is the resistance between A and B? C and D?
What is the resistance between A and AB?
What is the resistance between CD and the point I labeled 'CD?'?

Moving on to the second transformer, does the circuit running from E to E1 go through the small transformer I've labeled with E2 and E3?

Next, I forgot to label two of the pins on the three larger transformers. For convenience, we will call them T1-1, T1-2, etc. (T1 is the transformer on the right). Are T1-1, T2-1, and T3-1 connected together? T1-2, T2-2, and T3-2 each seem to be connected to a pair of capacitors. Are the capacitors connected to a common bus?

What I think I know: Each transformer consists of a single primary and two center-tapped secondaries. A and B are the ends of one secondary, AB is the center tap. C and D are the ends of the other secondary on T3; CD is the center tap. And so on. The center tap is used to monitor the current through each CCFL.

What you should do:
Answer the questions above by checking resistances. If my conclusions seem to be correct, measure the resistance of each secondary half as accurately as possible. A to AB; B to AB; C to CD, D to CD, and so on for all transformers. We are looking for a winding that is significantly (5% or more) different than the rest.

If everything checks out so far, I will need more information. I've circled two small ICs. What is the part number of them? Also, I've circled the legend for the main connector. I can read some of the information, but the top three lines elude me. HELP!!!

PlainBill

[JeremyR]

Re: Samsung Syncmaster 245BW

Does A connect to A1, B to B1, etc?

Yes to all

Is the small circle between A and A1 actually the circuit trace connecting A to A1?

Yes to all

What is the resistance between A and B? C and D?

approx .9 ohms for all (using an analog tester)

What is the resistance between A and AB?

Zero

What is the resistance between CD and the point I labeled 'CD?'?

approx 4.5 ohms

Moving on to the second transformer, does the circuit running from E to E1 go through the small transformer I've labeled with E2 and E3?

Yes

Next, I forgot to label two of the pins on the three larger transformers. For convenience, we will call them T1-1, T1-2, etc. (T1 is the transformer on the right). Are T1-1, T2-1, and T3-1 connected together?

Yes. All of them are all connected to each other (T1-1 is connected to T1-2, T2-2, T3-2 also).

T1-2, T2-2, and T3-2 each seem to be connected to a pair of capacitors. Are the capacitors connected to a common bus?

?? Not exactly sure what you mean here. The caps are connected to each of the Tx-x pins (all 6 of them).

If my conclusions seem to be correct, measure the resistance of each secondary half as accurately as possible. A to AB; B to AB; C to CD, D to CD, and so on for all transformers. We are looking for a winding that is significantly (5% or more) different than the rest.

I can't get any reading for any of these connections????

I've circled two small ICs. What is the part number of them?

A393F 801

Also, I've circled the legend for the main connector. I can read some of the information, but the top three lines elude me.

EX-PWM
A-DIM
ON/OFF

Very appreciative of your time and help...thanks!
Jeremy

[PlainBill]

Re: Samsung Syncmaster 245BW

A393F 801

EX-PWM
A-DIM
ON/OFF

Very appreciative of your time and help...thanks!
Jeremy

Some things do not make any sense. I would have expected about 1K ohms between A and AB; about 2K between A and B.

Let's try an approach without any preconceived assumptions. Let's work with T1. Set your ohmmeter on the highest range, then measure the resistance from pin 1 to 2, 1-3, 1-4 etc. Next, measure from 2-3, 2-4, 2-5, etc. Continue like this starting with pin 3, pin 4, etc, until you have measured the resistance between all pins. I would expect most of these to read open. When you post the chart, use a dash (-) to indicate open.

Next refine those readings that showed some continuity. Reduce the range for each of them until you get as accurate a reading as possible. Then I will see if I can figure out the winding pattern on the transformer.

PlainBill

[JeremyR]

Re: Samsung Syncmaster 245BW

Some things do not make any sense. I would have expected about 1K ohms between A and AB; about 2K between A and B.

Let's try an approach without any preconceived assumptions. Let's work with T1. Set your ohmmeter on the highest range, then measure the resistance from pin 1 to 2, 1-3, 1-4 etc. Next, measure from 2-3, 2-4, 2-5, etc. Continue like this starting with pin 3, pin 4, etc, until you have measured the resistance between all pins. I would expect most of these to read open. When you post the chart, use a dash (-) to indicate open.

Next refine those readings that showed some continuity. Reduce the range for each of them until you get as accurate a reading as possible. Then I will see if I can figure out the winding pattern on the transformer.

PlainBill

Well, I've got some readings for you, but I can not get any reading from any of 1-4 to any of 5-8. My meter is a bit old, but still seems to mostly work ( I have a x10K range setting that does not work nor does my x1 setting, so I guess it's within reason to say the readings I am getting are inaccurate). I'll let you decipher what I have.

Jeremy

[PlainBill]

Re: Samsung Syncmaster 245BW

Well, I've got some readings for you, but I can not get any reading from any of 1-4 to any of 5-8. My meter is a bit old, but still seems to mostly work ( I have a x10K range setting that does not work nor does my x1 setting, so I guess it's within reason to say the readings I am getting are inaccurate). I'll let you decipher what I have.

Jeremy

How about a picture of your meter? It appears pins 2-3 are the primary, and 5-6 and 7-8 are the secondaries, but the readings do not make sense. It MIGHT be that you are not accounting for the range setting properly, but even that doesn't make a lot of sense.

PlainBill

[Cortes121]

Re: Samsung Syncmaster 245BW

Jeremy, I do not mean to hijack your thread, but I too have a similar problem with the Samsung 245bw. I have also taken the monitor apart. My problem though is that the screen does not come on at all. I believe it to be the inverter.

EDIT: I am just at a loss to what to replace now..

[PlainBill]

Re: Samsung Syncmaster 245BW

Jeremy, I do not mean to hijack your thread, but I too have a similar problem with the Samsung 245bw. I have also taken the monitor apart. My problem though is that the screen does not come on at all. I believe it to be the inverter.

EDIT: I am just at a loss to what to replace now..

Does the power LED come on? If it does, then the monitor is coming on, it's just not displaying anything. That COULD be the inverter. Did you check the fuse on the inverter? Do you have power to the inverter? What voltage is on the On/Off pin?

PlainBill

[xoulu]

Re: Samsung Syncmaster 245BW

how do you take one apart? I am trying to replace the LCD light but I am not sure on how to take one apart? Can anyone help me out? Thank You

[xoulu]

Re: Samsung Syncmaster 245BW

how do you take one apart? I am trying to replace the LCD light but I am not sure on how to take one apart? Can anyone help me out? Thank You

Sorry but what I mean was how do you take the CCFL apart?

[Cortes121]

Re: Samsung Syncmaster 245BW

Does the power LED come on? If it does, then the monitor is coming on, it's just not displaying anything. That COULD be the inverter. Did you check the fuse on the inverter? Do you have power to the inverter? What voltage is on the On/Off pin?

PlainBill

The power LED does come on. I need the check the fuse and also check to see if I am getting power to the inverter and get a voltage reading. I am quite a noob at this though, I am not sure what the inverter for this model looks like. if it is the board that you marked earlier in the thread, with several black wires running to the screen, then where on it is the fuse? Will a normal multimeter work for determining power is reaching the inverter? Where is the on off pin?

Again, sorry if I am too inexperienced

[PlainBill]

Re: Samsung Syncmaster 245BW

The power LED does come on. I need the check the fuse and also check to see if I am getting power to the inverter and get a voltage reading. I am quite a noob at this though, I am not sure what the inverter for this model looks like. if it is the board that you marked earlier in the thread, with several black wires running to the screen, then where on it is the fuse? Will a normal multimeter work for determining power is reaching the inverter? Where is the on off pin?

I've marked up the picture to indicate where the test points are. Given your level of expertise, I suggest you do this with someone else on hand to cut the power if you make a mistake.

Set your DMM to measure DC, 200 volt scale; hold the black lead on any of the pins marked Gnd. Measure the voltage on the On/Off pin, any of the power pins, and if you get a reading on a power pin, measure the voltage on the lower end of the fuse (the tiny white block with the silver ends).

Again, sorry if I am too inexperienced

Don't worry. One way or another you will be getting a LOT of experience.

PlainBill

[Stebono]

Re: Samsung Syncmaster 245BW

I too have the same monitor and it will turn on and stay on but the screen blanks out after several seconds. If I turn it off for a bit and turn it back on it may start displaying video again, but is questionable if it stays on and is getting worst. So like the other two I thought I'd pull it apart and try to get a schematic to repair and came across this wonderful site with experienced people with monitor repair. I have an electrical degree but haven't played with circuit diagnostics for many years.

I've gone through the initial readings that Jeremy did and got better results that should fall into what you would expect to see.

So if you're still around Bill or anyone else who knows these monitors I would appreciate a hand if you have the time. My setup is identical to Jeremy's so I just used the already pasted pictures and instruction and refilled them with my readings.

Please review:

Does A connect to A1, B to B1, etc?

Yes to all

Is the small circle between A and A1 actually the circuit trace connecting A to A1?

Yes to all (Except for points E -> E2 [coil] E3 -> E1 (coil resistance 32.1 ohms)

What is the resistance between A and B? C and D?

A -> B = 1.820K ohms
C -> D = 1.796K ohms
E -> F = 1.792K ohms
G -> H = 1.757K ohms
I -> J = 1.807K ohms
K -> L = 1.788K ohms

What is the resistance between A and AB?

Open (infinate) for all simular points

What is the resistance between CD and the point I labeled 'CD?'?

Zero (trace connects two points making them the same point)

Moving on to the second transformer, does the circuit running from E to E1 go through the small transformer I've labeled with E2 and E3?

Yes (tranformer is in series to E & E1)

Next, I forgot to label two of the pins on the three larger transformers. For convenience, we will call them T1-1, T1-2, etc. (T1 is the transformer on the right). Are T1-1, T2-1, and T3-1 connected together?

They are called T1 to T3 (right to left order)

T1-1 -> T2-1 = 4.87M ohms
T1-1 -> T3-1 = 4.93M ohms
T2-1 -> T3-1 = 4.91M ohms

Individual Transformer Inputs
T1-1 -> T1-2 = 10M+++ (seems there is a cap associated with this point as the meter doesn't stabalize)
T1-1 -> T1-3 = 10M+++ (seems there is a cap associated with this point as the meter doesn't stabalize)
T1-1 -> T1-4 = 4.89M ohms

T1-3 -> T1-4 = 10M+++ (seems there is a cap associated with this point as the meter doesn't stabalize)
T1-2 -> T1-3 = Zero

T1-2, T2-2, and T3-2 each seem to be connected to a pair of capacitors. Are the capacitors connected to a common bus?

Actually no they don't seem to be at least not to GND or +V, they both have a potental from either bus.

If my conclusions seem to be correct, measure the resistance of each secondary half as accurately as possible. A to AB; B to AB; C to CD, D to CD, and so on for all transformers. We are looking for a winding that is significantly (5% or more) different than the rest.

They are all open in relationship, top side seems to be inputs (two windings tied together at points Tx-2 & Tx-3) to tranformer and bottom side feeding CCFL seem to be outputs.

I've circled two small ICs. What is the part number of them?

A393F 808

Also, I've circled the legend for the main connector. I can read some of the information, but the top three lines elude me.

EX-PWM
A-DIM
ON/OFF
SOS
GND
GND
GND
GND
GND
+24V
+24V
+24V
+24V
+24V