Samsung 226BW

[CRi]

Hello,

I have a problem with my Samsung 226BW.
The display stopped working, the power led would not turn on.
I opened the monitor, and surely enough, the 6 big caps on the power supply were blown (5x 820µf, 1x 330uF).

I replaced them with new panasonic caps and the PSU came back to live. Sadly, the controller board was toast... I ordered another controller (same model) and replaced it.

The display is now working with a HDMI signal (I couldn't test the VGA input as I don't have a cable on hand). But when it has no input signal, it displays a strange pattern instead of a black screen or "check input" message (see attachment).

What could be wrong? Is the replacement controller defective?

Any help would be very welcome.
Thanks in advance

Cédric

[selldoor]

Re: Samsung 226BW

Looks like the panel is defective -is the lvds cable in the right way round and a good fit. did you get anything at all using the old controller.
With a hdmi connector does the pc still get the edid information - what does it think it is connected to?
You are likely to get more/better help if you post pictures of your boards, inc the old controller.

[CRi]

Re: Samsung 226BW

Looks like the panel is defective -is the lvds cable in the right way round and a good fit. did you get anything at all using the old controller.
With a hdmi connector does the pc still get the edid information - what does it think it is connected to?
You are likely to get more/better help if you post pictures of your boards, inc the old controller.

Maybe I wasn't clear but it works fine when it has a signal on its HDMI input. Those strange patterns only appear when it ha NO input signal.

I know this is a minor annoyance, it appears on once at each boot, but if it is simple to fix I would prefer to do it :-)

[selldoor]

Re: Samsung 226BW

Oh! not seen that before maybe others have- If not perhaps try a factory reset if
it is on the menu - assuming the menus work ok?

[CRi]

Re: Samsung 226BW

Oh! not seen that before maybe others have- If not perhaps try a factory reset if
it is on the menu - assuming the menus work ok?

The menus are working, I tried "Image reset" and "Color reset" but it didn't fix the problem. I didn't find a "factory reset" menu.

I had a change to try the VGA input and it's working too.

So I guess it's no big deal

[budm]

Re: Samsung 226BW

Can we see the pictures of the main/logic/scaler board?
It may be caps problem on the main board or power supply board. Try heating the main board with hair dryer.
I have seen this problem on SAMSUNG TV with bad cap in the power supply.

[CRi]

Re: Samsung 226BW

Here are the pictures of the controller.

Sorry for the quality, it's not easy to take good macro pictures without proper lighting

I have a cheap rework station, I can try to heat the board. What should I do? Heat it then plug it, or heat it while powered on??

Do you want pictures from the power supply too?

[leggot]

Re: Samsung 226BW

I have seen a similar problem with a similar model. The fix ended up being reflowing the main chip. Try using a hair drier to heat up the main chip, or compressed air can upsidedown to see if it has an effect on the signal.

While running, heat up the board to see if anything changes.

[budm]

Re: Samsung 226BW

Use hair dryer unless you can reduce the heat of your rework station, just heat up the whole board first to see if it has positive affect on it.

[CRi]

Re: Samsung 226BW

I have heated the logic board, but that did not fix the problem.
Sometimes the line pattern changed but it never disappeared.

I don't have a can of compressed air to cool it...

It's really strange that it only appears when it has no signal, isn't it?
If the main chip need to be reflowed, wouldn't the problem be present all the time?

[momaka]

Re: Samsung 226BW

If the main chip need to be reflowed, wouldn't the problem be present all the time?

Indeed. Most likely not a chip issue (in my opinion).

It's really strange that it only appears when it has no signal, isn't it?

Yes, it is.
The only thing I can think of is partially-corrupt BIOS for the "No Signal" image. Most likely caused by unstable power when the original caps went bad.

As selldoor mentioned in post #2, what name does the monitor appear with when you connect it to your computer? Does it appear as a "regular" PnP (Plun n Play) monitor or does the name/model of the monitor appear as well? Or any other funny stuff?

[CRi]

Re: Samsung 226BW

Indeed. Most likely not a chip issue (in my opinion).


Yes, it is.
The only thing I can think of is partially-corrupt BIOS for the "No Signal" image. Most likely caused by unstable power when the original caps went bad.

As selldoor mentioned in post #2, what name does the monitor appear with when you connect it to your computer? Does it appear as a "regular" PnP (Plun n Play) monitor or does the name/model of the monitor appear as well? Or any other funny stuff?

I finally got a little bit of time to try and repair this monitor

So I checked in the device manager and it is recognized as "SyncMaster 226BW". Edid Viewer Utility is able to read all EDID information.

If the BIOS is corrupted, is it possible to flash it? Or maybe swap the eprom of both controllers?

Does the eprom contain information specific to the panel? Mays both controllers come from different panels and therefore contain incompatible information?

[Agent24]

Re: Samsung 226BW

The EDID EEPROM(s) and main system EEPROM are separate chips usually (or always). Sometimes the main system program is not in a separate chip, but inside the microcontroller itself.

[CRi]

Re: Samsung 226BW

I recently bought a Rigol DS1054Z so I tried to measure the 13.5V coming from the power supply. I'm a scope noob so forgive me if I'm wrong...

The power supply seems awful to me, very badly filtered.
It seems to have more than 1V ripple !

See attached screenshots (always the same signal, but different zoom settings).

I already changed most of the electrolytic caps on the PSU, it wouldn't start without that.

What do you think?

[Agent24]

Re: Samsung 226BW

When measuring ripple you have to do it correctly otherwise you risk getting false results from interference.

https://www.youtube.com/watch?v=Edel3eduRj4

[budm]

Re: Samsung 226BW

What did you use for the GND ref? Are you using very short GND LEAD for the probe?
Look at the frequency as shown on the display:
CUR: 18.5MHz
AVG: 20.3MHz
MAX: 96.2MHz
MIN: 7.79MHz.

You are picking up stray signals form some where.

[CRi]

Re: Samsung 226BW

When measuring ripple you have to do it correctly otherwise you risk getting false results from interference.

https://www.youtube.com/watch?v=Edel3eduRj4

Damn, I had already watched that video when Dave released it, but I didn't have a scope at that time... you were right, I was measuring it all wrong

What did you use for the GND ref? Are you using very short GND LEAD for the probe?
Look at the frequency as shown on the display:
CUR: 18.5MHz
AVG: 20.3MHz
MAX: 96.2MHz
MIN: 7.79MHz.

You are picking up stray signals form some where.

So now I used the springy ground lead, set my probe to 1x, bandwith limit to 20mhz,...

The results are much better

Seeing that this problem appears only when no video signal is present, I think I'll just leave it that way... I guess it's a problem with the replacement driver board but that's no big deal.