Samsung SyncMaster 204b

[Freezer]

Recently I was given two broken Samsung monitors; a 204b and a 225bw. I'll talk about the 225bw in this thread.

The 204b shares the same power/inverter board with the 225bw. The 225bw had 4 obviously bad caps. The 204b had no obvious cap problems. I do not have a cap tester, and since I was already ordering parts for the 225bw I went ahead and re-capped the 204b as well. I replaced C110 and C111 with 820uF 25V United Chemi-con LXY caps (digikey pn 565-1800-ND). I also replaced C112, C304, and C305 with 330uF 25V Panasonic FM caps (digikey pn P12386-ND).

After the recap the monitor turns on, the backlights power on, but the screen is partially messed up. The top 1/3 of the screen is normal. But the bottom 2/3s of the screen is scrambled and useless. It does not matter which video input is used, even with no video input the "no input" screen is messed up on the bottom. I suspect the video board is the problem, but I don't see anything obviously wrong on the video board. Any suggestions?

Attached to this post are close-ups of the front and back of both the power/inverter and video boards. I just realized I forgot to take a picture of the screen while the monitor is on. I'll try and get that picture posted soon.

[retiredcaps]

Re: Samsung SyncMaster 204b

Any suggestions?

Great pics. Post the messed up pics as well. In addition, can we also get a shot of the logic board with the cable that attaches to the LCD panel?

Troubleshooting the logic side is something I'm still learning, but I would check

1) cable from CN201 to LCD panel is not obviously broken or crimped.
2) check for continuity using DMM from CN201 to LCD panel to make sure the cable isn't internally broken.
3) measure voltages at CN201 when monitor is on
4) examine CN201 traces back to main MST6281LA chip to ensure there is continuity using DMM
5) check MST6281LA chip for bad solder joints using magnifying glass
6) maybe check voltage regulators to ensure they are outputting the proper voltage

[Freezer]

Re: Samsung SyncMaster 204b

As promised here are the remaining pics of this monitor.

The first is a picture of the screen while running (no the screen is not bent, I was too close to the screen and got barrel distortion from my camera lens). Also the second video board. Because of the long narrow aspect ratio of the second video board, I broke the picture in half; the left half on the top and the right half on the bottom.

[Freezer]

Re: Samsung SyncMaster 204b

retiredcaps - thanks for the great suggestions. I didn't think to use a multimeter to check that cable and traces on the circuit board. I don't have time tonight, but soon I'm going to bust out the multimeter and try that.

Regarding tests 3 and 6 - I compare voltage while the monitor is running against a grounded part of the monitor, correct?

[retiredcaps]

Re: Samsung SyncMaster 204b

I didn't think to use a multimeter to check that cable and traces on the circuit board.

Regarding tests 3 and 6 - I compare voltage while the monitor is running against a grounded part of the monitor, correct?

You should get 0.3 or 0.4 ohms when tracing out the cable and traces.

For test 3, pick a ground screw and put your (black) COM there. Put your red probe on the pins at CN201. I'm guessing the first 2 pins will be 5V DC and all the others in the 1.2V DC range?

For testing the voltage regulators, there are usually 3 pins. One is ground and one is "input" and one is "output". If you look at the markings on the voltage regulators, there should be a part number. Search for the datasheet and that will tell what is ground. Put your black probe on ground and then measure in and output voltage. It should match the datasheet exactly. All the voltage regulators should be measured with DC.

The other suggestion I have is actually looking at the LCD panel and making sure there are no obvious burn/bad connections.

I'm having a hard time visually seeing the "big picture" with long video boards. Can you put everything (power, logic, inverter, cables) laid out into one picture? That way, I can see what connects to what and where. A top down view. The details aren't important in this picture, I just want to see the whole thing.

[retiredcaps]

Re: Samsung SyncMaster 204b

This is what I mean. See PlainBill's pic of a plasma

https://www.badcaps.net/forum/attach...chmentid=16900

It will help troubleshoot why the bottom 2/3rds is not displaying correctly.

Can you put everything (power, logic, inverter, cables) laid out into one picture?

[Freezer]

Re: Samsung SyncMaster 204b

I'm having a hard time visually seeing the "big picture" with long video boards. Can you put everything (power, logic, inverter, cables) laid out into one picture? That way, I can see what connects to what and where. A top down view. The details aren't important in this picture, I just want to see the whole thing.

Sorry it took a while to get back to you, this has been one busy week. Anyway, attached is a picture of the layout of the back of the monitor. Note the labels "video 1" and "video 2" are names I'm using, they are not official Samsung terms.

I've also had a chance to use a DMM and check the ribbon cable between the video boards. It checks out fine. I'll check the other tests you suggest hopefully this coming week.

[retiredcaps]

Re: Samsung SyncMaster 204b

Anyway, attached is a picture of the layout of the back of the monitor.

Okay, that makes sense now. What is that big chip (with the black felt marker) on video board 2? Can you post the part number?

[Freezer]

Re: Samsung SyncMaster 204b

What is that big chip (with the black felt marker) on video board 2? Can you post the part number?

That chip reads as follows:

wiseview
LRU4312X1A
0613
KSA98

[retiredcaps]

Re: Samsung SyncMaster 204b

wiseview
LRU4312X1A
0613
KSA98

Darn, no datasheet on this chip or on the MST6281 chip.

This is a long shot, but did you try resetting this monitor back to factory defaults? See posts #186 to #197 (just before your post).

https://www.badcaps.net/forum/showth...&page=10&pp=20

[Freezer]

Re: Samsung SyncMaster 204b

This is a long shot, but did you try resetting this monitor back to factory defaults? See posts #186 to #197 (just before your post).

I tried that, but I can't tell if anything is happening. Because I can't see the lower 2/3s of the screen I can't tell if any of the menus work. I tried to do it by "feel" without looking at the screen, but no go. It doesn't help these service manual instructions were poorly translated from Korean to English.

1. Hidden Service Function -. After setting brightness and contrast '0' push the "Enter" button more than 5 seconds.

Are they saying turn the brightness and contrast all the way to their lowest setting? In which case how's one suppose to see the service menu? Also, it says to press the "Enter" button, except this monitor doesn't have a menu button.

[retiredcaps]

Re: Samsung SyncMaster 204b

Are they saying turn the brightness and contrast all the way to their lowest setting? In which case how's one suppose to see the service menu? Also, it says to press the "Enter" button, except this monitor doesn't have a menu button.

I don't think it will hurt to try the variations.

Did you get a chance to take those voltage readings on the connectors and voltage regulators? I'm hoping the readings will help narrow down the problem to either the logic card or the lcd panel.

[Freezer]

Re: Samsung SyncMaster 204b

Did you get a chance to take those voltage readings on the connectors and voltage regulators? I'm hoping the readings will help narrow down the problem to either the logic card or the lcd panel.

Sorry it took a while to post back. Using a DMM I checked some voltages at various points inside this monitor.

First, the power cable that runs from the power board to the video board. Several lines in that wire are spec'ed to carry 13V, and indeed they are carrying a steady 13V of power. Second, the video ribbon between the two video boards. There are several lines which are supposed to carry 5V which are delivering a steady 4.9V (which I'm assuming it fine). The remaining lines in the ribbon vary from .83V to 1.6V. A few of the wires read at 0V. I previously checked the cable for continuity and it checked out, so I'm assuming these 0V readings are normal.

At this point I think the monitor is beginning to take more time than I think it's worth. I also feel like I've become a drain on this forum, taking up everyone's expert advise with little to provide in return.

[retiredcaps]

Re: Samsung SyncMaster 204b

There are several lines which are supposed to carry 5V which are delivering a steady 4.9V (which I'm assuming it fine). The remaining lines in the ribbon vary from .83V to 1.6V. A few of the wires read at 0V. I previously checked the cable for continuity and it checked out, so I'm assuming these 0V readings are normal.

4.9 is fine. 0V is normal as some of those pins are probably ground.

At this point I think the monitor is beginning to take more time than I think it's worth. I also feel like I've become a drain on this forum, taking up everyone's expert advise with little to provide in return.

It is up to you if you want to continue. When no one responds to your posts, it means "we" have given up or we have no more suggestions.

I'm happy to provide more suggestions, but if you don't have the time, recycle it on craigslist/kijiji and maybe someone else can use it for parts.

[PlainBill]

Re: Samsung SyncMaster 204b

Sorry it took a while to post back. Using a DMM I checked some voltages at various points inside this monitor.

First, the power cable that runs from the power board to the video board. Several lines in that wire are spec'ed to carry 13V, and indeed they are carrying a steady 13V of power. Second, the video ribbon between the two video boards. There are several lines which are supposed to carry 5V which are delivering a steady 4.9V (which I'm assuming it fine). The remaining lines in the ribbon vary from .83V to 1.6V. A few of the wires read at 0V. I previously checked the cable for continuity and it checked out, so I'm assuming these 0V readings are normal.

At this point I think the monitor is beginning to take more time than I think it's worth. I also feel like I've become a drain on this forum, taking up everyone's expert advise with little to provide in return.

There are two possibilities; either the logic card (which probably be called the video card or control card), or the panel card (I believe retiredcaps refers to it as video board 2). It certainly doesn't look like a power supply issue, which eliminates the voltage regulators on the logic card.

I'd have to say that the best move would be to shelve it until another 204b falls into your hands; I suspect you will find this one has a bad panel card.

PlainBill

[Juluscesar]

Re: Samsung SyncMaster 204b

Have the same problem. 1/3 of my samsung syncmaster is OK below 2/3 part is missed up. Just came sudden making a word document on my machine.

Any solution yet ?

[Tomato]

Re: Samsung SyncMaster 204b

hey folks,

Sorry to resurrect such an old thread but....I've got virtually exactly the same issue. I replaced the obviously bad 'lytics on the inverter board, and then some (upgrade from CapXon's to Nichicon's can't hurt, right?). But I don't think this is a power supply problem! I have rudimentary knowledge of power supplies, but the video board is total black magic to me! Any solutions found? Or, can anyone point me in some direction or another? I inspected the video board and everything is clean, traces are intact, wires are all intact. How might I solve this?

Any help is appreciated,
Tomato

[retiredcaps]

Re: Samsung SyncMaster 204b

I've got virtually exactly the same issue.

If you hookup a working computer showing your favourite wallpaper, can you see it if you shine a flashlight on the lcd?

It would help to have clear focused pictures of your boards so we can indicate out test points. Please use the manage attachments function to upload your pictures (2000x2000 is the max resolution). Please do not post pics inline as they slow down the loading of pages.

[john98103]

Re: Samsung SyncMaster 204b

I have this same power supply. main characteristic of my problem is a blank screen and power light glows blue for a short moment and then turns off. I replaced C110 and C111 with 820uF 35V which were obviously bad and I replaced the three 330uF 25V which looked OK. This did not fix my problem. I'm most curious what the power light OFF might indicate.

[PlainBill]

Re: Samsung SyncMaster 204b

I have this same power supply. main characteristic of my problem is a blank screen and power light glows blue for a short moment and then turns off. I replaced C110 and C111 with 820uF 35V which were obviously bad and I replaced the three 330uF 25V which looked OK. This did not fix my problem. I'm most curious what the power light OFF might indicate.

It could indicate a number of things. A first step is to measure the voltages out of the power supply.

PlainBill