Samsung Syncmaster 204BW

[ben7]

Got this monitor, first when I turned it on the screen was red then it started slowly changing colors. So, I opened it up, and found 3 bulged capXons. Replaced them and now the monitor comes on, but its all red!

The VGA cable is fine (tested with another monitor). I re-seated all connectors but it still hasn't gotten better. Any Ideas? I will measure some voltages and get some pics up in a little while.

[ben7]

Re: Samsung Syncmaster 204BW

Ok, 13v reads good, 3.3v reads good, and ?1.5v? reads 1.6v; all measured on the logic board. :/ As far as I can see, all fuses on the board read good also.

[selldoor]

Re: Samsung Syncmaster 204BW

Is that with a source, can you try with dvi on that model?
Check back of the vga socket for dirt /solder balls.
Is it red without any source?

[ben7]

Re: Samsung Syncmaster 204BW

Is that with a source, can you try with dvi on that model?
Check back of the vga socket for dirt /solder balls.
Is it red without any source?

Sorry, I don't have a DVI cable :/

Without any source, there is no picture at all!

The solder on the VGA connector is questionable, but wiggling the connector doesn't change the image. I might try reflowing it later.

Also, it appears that when the screen is on (displaying a red image) that there is some sort of scrambled thing in the middle of the screen.

[selldoor]

Re: Samsung Syncmaster 204BW

Just seen the pic the inverter caps look a bit bulged (Are They) and they are capxon?
Not sure that that would affect the colour though.

[ben7]

Re: Samsung Syncmaster 204BW

Just seen the pic the inverter caps look a bit bulged (Are They) and they are capxon?
Not sure that that would affect the colour though.

Yes they are CapXon, with them the monitor is blue/green at first, then it slowly changes color to red over a few secs.

I have replaced them with good rubys and Nichicons but now I am having this red picture problem :/

[tom66]

Re: Samsung Syncmaster 204BW

Reseat the LVDS connector going to the T-con.

[ben7]

Re: Samsung Syncmaster 204BW

Reseat the LVDS connector going to the T-con.

I did that, and the screen went wacky the first time I started it up (the screen was random bars of color, which started to change color to red). The second time it was red only again ...

Do you think the T-con is fried by the excessive voltage ripple from the old capXon caps?

[selldoor]

Re: Samsung Syncmaster 204BW

Can you do picture front and back of the other boards.

[ben7]

Re: Samsung Syncmaster 204BW

1. PSU front
2. PSU back
3. Mobo front
4. Mobo back

I was having trouble getting good pics with the light in my room, so I might have to take some more later, if you want xD

Edit: I had trouble getting good focus on the T-con board

[jetadm123]

Re: Samsung Syncmaster 204BW

Ok, 13v reads good, 3.3v reads good, and ?1.5v? reads 1.6v; all measured on the logic board. :/ As far as I can see, all fuses on the board read good also.

Did you read the 3.3v and 1.6V output directly off the voltage regulators on the logic board? The 3.3V sounds good. The 1.6V regulator might be labeled something like 1117-18, which indicates a 1.8V output. If yes, then the 1.8V regulator looks a little off spec and would possibly indicate a bad regulator or bad output cap.

[ben7]

Re: Samsung Syncmaster 204BW

Did you read the 3.3v and 1.6V output directly off the voltage regulators on the logic board? The 3.3V sounds good. The 1.6V regulator might be labeled something like 1117-18, which indicates a 1.8V output. If yes, then the 1.8V regulator looks a little off spec and would possibly indicate a bad regulator or bad output cap.

Aha, it is 1117

I looked up the data sheet, and it came up with an adjustable LDO, but I might have found the wrong one.

[jetadm123]

Re: Samsung Syncmaster 204BW

If there's a '18' stamped on the regulator, then it's fixed output. This regulator is made by many companies. You can use the datasheet below as a reference:

[budm]

Re: Samsung Syncmaster 204BW

If it is adjustable then take the reading between pin 1 and pin 2, it must be 1.25V if it is OK.

[ben7]

Re: Samsung Syncmaster 204BW

Back, it does have 18 stamped on it, and its outputting 1.6V not 1.8V. Do you think the regulator could be bad, or could something be loading down the output?

[budm]

Re: Samsung Syncmaster 204BW

That is 11% off, yes the really heavy load may cause the problem or just bad regulator. I would try a new one.

[retiredcaps]

Re: Samsung Syncmaster 204BW

Back, it does have 18 stamped on it, and its outputting 1.6V not 1.8V. Do you think the regulator could be bad, or could something be loading down the output?

Since there are no electrolytic caps on the main board, my guess is that the regulator itself is bad. I use a +/- 1% rule for regulators.

In this subforum, most of the problems (I'm guessing 90%+) are the regulators itself and not some component around it.

[retiredcaps]

Re: Samsung Syncmaster 204BW

Do you think the regulator could be bad, or could something be loading down the output?

If you are really good at removing SMD devices, it would be really easy to test the regulator itself with a couple of AA batteries in series or a 3V CR2032 battery.

[ben7]

Re: Samsung Syncmaster 204BW

Since there are no electrolytic caps on the main board, my guess is that the regulator itself is bad. I use a +/- 1% rule for regulators.

In this subforum, most of the problems (I'm guessing 90%+) are the regulators itself and not some component around it.

You sure the caps aren't electro's? They are in a can, but they could be polys I guess; I cant tell the difference xD

I guess I will order some parts soon then, since I have a list of parts I want for other projects too. And I need some more caps.

[ben7]

Re: Samsung Syncmaster 204BW

OMG I am excited!

https://www.badcaps.net/forum/showthread.php?t=20879

I did the EEPROM (same chip in this one) reset, and the menu and buttons worked for a min or two! (The screen was still mostly red) Then it went back to the garbled up state again. I am guessing there is a bad capacitor or two on the processing board too, and maybe a bad regulator (LM1117) - time to order some parts!

I found a 5v rail on the board too, it has a buck smps. I measured the 5v and it was about 4.7v, and I measured AC voltage, and it was almost half a volt! no wonder there is problems! I think the failed PSU caps put excess stress on these, so they failed, and made the screen garbled up (excessive AC ripple).