Samsung syncmaster 205bw

[Dixie]

Hi All.

Great forum!!! I thought you had help me resolve my problem however after changing the caps im still no further forward.

The story is:

I have a Syncmaster 205 BW. For some time is been sat around due to it not working. The blue power light comes on but no picture. No flickering or anything just total bleak darkness

So i though i'd see if i could fix it. Took the back of and sure enough some of the caps were swollen. So today i've replaced 5 of them. The 4 1000uf ones and the "other" one. Leaving the big hitter one and the very small one alone.

After putting it all back together i have exactly the same problem. No change what so ever.

So....

Could i have done something wrong? ie cooked the Caps with the iron. It's quite a nasty one and i'm by no means a pro.

Or is there anything else it could be and what can i do to test it?

Thanks in advance

Matt.

[Scenic]

Re: Samsung syncmaster 205bw

checked the inverter fuse?

[Dixie]

Re: Samsung syncmaster 205bw

Hmmm. Forgive my stupidness. But I'm not sure where the fuse would be. I can't see a resistor size on anywhere. Can someone point me in the right direction??

I take it a simple continuity test is enough?

Thanks again.

[jetadm123]

Re: Samsung syncmaster 205bw

Okay, this is how it goes....we need to see good focused photos of the top and bottom of the entire power supply board. Also, a photo of the logic board would be good. Multiple power supplies from different manufacturers were used on this monitor and trying to second guess what you have without photos is painful. By now, you've probably figured out that members telling you to check something without really pointing out where that "something" is located, just adds to the confusion and wastes everyone's time. Plain and simple, we need to see what you're seeing in order to help.

[Dixie]

Re: Samsung syncmaster 205bw

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Hows that??

Caps changed are the 3 on the left and the two top center.


Is the fuse the round red thing just behind the power switch and socket?

[jetadm123]

Re: Samsung syncmaster 205bw

1) What brand and series caps did you use as replacements? Ideally, you should also have replaced the small cap, since it is part of the startup circuit.

2) You say you used 1000uf caps as replacements. Was that the value of the original caps also 1000uf?

3) With the monitor connected to a running computer, if you shine a flashlight against the dark screen can you see a faint image of the desktop?

4) There are two devices mounted on the heatsink on the left side. These output the 5V for the logic board and LCD panel and 12V-14V for the inverter section. With your meter set to DC volts, measure the middle leg of each device and report voltage readings.

5) Yes, F101 is the main fuse, but it's probably ok, since you're getting the power light.

[Behemot]

Re: Samsung syncmaster 205bw

Same problem, only blue LED under on/off button which even do nto react on pressing it. In other threads I found that it may be inverter transformers which I probably won't be able to find, so that's the end?

[PlainBill]

Re: Samsung syncmaster 205bw

Same problem, only blue LED under on/off button which even do nto react on pressing it. In other threads I found that it may be inverter transformers which I probably won't be able to find, so that's the end?

It may be, but don't give up without a little testing. In most cases if you trace the inverter supply from the filter caps to the transformer drivers you will find you can disable the inverter by lifting a jumper. If the power LED still does not react with the inverter disabled, you have isolated the problem to either the logic card or the main supply.

PlainBill

[alexanna]

Re: Samsung syncmaster 205bw

One other thing I have noticed, Is if you have no back light activity and you have a power LED on but you are unable to turn the monitor on and off with the front panel power switch. Upon disconnecting the LDVS cable to the LCD I had normal back light and power switch operation. The problem turned out to be a 1.8volt regulator on the logic or signal board that the output was really low at just above 1 volt. This was on an Acer monitor. But I think the point may be that there was a less load on the monitor by disconnecting the panel it was able to somewhat work.
Voltage regulators are relatively easy to check.

[juggernaut]

Re: Samsung syncmaster 205bw

Hello - I have the exact same monitor and boards as shown in the above post. Samsung SyncMaster 205BW. I did much the same as Dixie and replaced all the caps except the very large one and the very small one. Same symptoms as well, un responsive blue power light, no flickering or blinking, no light whatsoever. I have a limited knowledge of electronics but eager to learn. Above Dixie was instructed to check the middle leg of the heatsink mounted devices. What would I put the testers too? The + to the middle leg and the - to the outer? Any other suggestions would be excellent. Also could anyone recommend a good cap tester? Can a cap be tested in the board?

Thank-You

[PlainBill]

Re: Samsung syncmaster 205bw

Hello - I have the exact same monitor and boards as shown in the above post. Samsung SyncMaster 205BW. I did much the same as Dixie and replaced all the caps except the very large one and the very small one. Same symptoms as well, un responsive blue power light, no flickering or blinking, no light whatsoever. I have a limited knowledge of electronics but eager to learn. Above Dixie was instructed to check the middle leg of the heatsink mounted devices. What would I put the testers too? The + to the middle leg and the - to the outer? Any other suggestions would be excellent. Also could anyone recommend a good cap tester? Can a cap be tested in the board?

Thank-You

The 'heat sink mounted devices' are diodes. These particular ones are schottky diodes and are used to rectify the output of the SMPS transformer.

I recommend a two step approach to testing diodes. The first is to set the DMM to the 200 ohms range and check the resistance across the diode - middle to either side. Polarity isn't important because the voltage is too low to cause the diode to conduct, so the diode should show a resistance greater than 200 ohms - OL. Next, set the DMM to the diode test range and check in both directions. You should get a reading of less than .5 for a schottky diode in one direction only.

There are three tests that can be performed on capacitors - capacitance, leakage, and ESR. For monitors, capacitance and ESR are the important values. A rough test can be done in circuit, in case of doubtful results testing out of circuit is essential. It is vital you be aware of circuit topology - two or more capacitors in parallel should show a fraction of the ESR of the individual caps.

For general purpose use, I suggest the ESR Micro V4.0. It measures both Capacitance and ESR, and is relatively inexpensive. Information is here.

PlainBill

[quicknick]

Re: Samsung syncmaster 205bw

Hello - I have the same monitor, same board versions, same problem.
Replaced three bulging caps, nothing happened, blue power led remains lit after power is applied and nothing else works (13V output from the PSU board is ok). Even replaced the two 1000uF/25V caps that were not swollen - same thing. Has anyone successfully repaired a 205BW that shows these symptoms?

[selldoor]

Re: Samsung syncmaster 205bw

Same monitor and boards as who - it is far easier for us to help if you post pictures of your own pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

Your boards might have heat marks cold joints different layout/caps
and components.
Does the power switch not work at all after the switch on - ie you cannot switch it off.
When it is on, with a pc connected on a vivid screen can you see that
faintly on the monitor - perhaps using a torch.

[quicknick]

Re: Samsung syncmaster 205bw

Same monitor as the one we're discussing in this thread, Samsung 205BW. Same boards as Dixie's - i noticed there are many different layouts, but his boards are identical to mine. I'll post pictures in a few days, no camera at the moment. Same symptoms as those described by Dixie and others in this thread - power led stays solid blue, cannot turn off, backlight stays off.
Power supply is ok after replacing the swollen caps, today I checked the 3.3v and 1.8v regulators on the signal board and their output is ok. The three wires labeled BL_EN, BL_ANALOG and BL_PWM between power supply and signal boards are at 0 volts. Can i "trick" the PSU board to enable the backlight by connecting some of these signals to a higher voltage?
Thanks in advance.

[vedge]

Re: Samsung syncmaster 205bw

Hello there, nice topic here!

I just changed the caps (1x 470uF 25V, 4x 1000uF 25V, 1x 10uF 50V) because my 205bw had a red screen. Unfortunately the problem stays the same.
The OSD appears in normal colors. MENU Button didn't work, Power Button only works when no display cable is connected.

Do ya have any ideas?

http://img833.*************/img833/1861/foto1ab.jpg
http://img707.*************/img707/818/foto2nv.jpg

Thanks so much!

[budm]

Re: Samsung syncmaster 205bw

Red tinted means the monitor is not getting all 3 color signals from the PC video card, check the video cable and connector seating or try it on another PC.

[vedge]

Re: Samsung syncmaster 205bw

Thanks for your answer, but i already tried different cables, PCs and both inputs (DVI & VGA/RGB) but the red tint stay the same.

And as i mentioned above the buttons didn't work correct too. So i think its a different problem.

Somewhere else i read "The red or pink tint indicates that the back light florescent bulbs are failing.". But this can't be reason if the OSD still appears in correct colours?

[selldoor]

Re: Samsung syncmaster 205bw

We are suffering from a distinct lack of pictures of the boards in this thread.
Please can you post some as per my request to other posters.
You could still check the sockets for bent /broken pins but as you say
you have tried vga and dvi it is unlikely that is the problem.

I once had a small tv that showed everything in green and I believe this was
due to the main processor on the main/video board becoming detached from the board. I cured it by packing.

As a test when the tv is on, locate the main processor and press on it gently with a wood or plastic rod - around the edges so you put pressure on the pins. = Watch on the screen for changes. Applying gentle heat with a hair drier may also change the output from the processor

EDIT
You could also try removing cleaning and replacing the LVDS cable between the main board and the panel

[Behemot]

Re: Samsung syncmaster 205bw

You checked the video cable to the panel itself?

[vedge]

Re: Samsung syncmaster 205bw

Hello again, thanks for your tips! I tried pressing the main processor and other elements of the main board but nothing changes the output. I also checked and shaked the LVDS cable (video cable to the panel) with no success.
And i would assume a defect with the LVDS cable or the panel itself couldn't explain the failing LCD buttons.

Here some pics of my boards:




Hope they are detailed enough?