Samsung monitor - 2232GW - power on issues (possibly not a caps fault?)

[SolderSucker]

I have a Samsung 2232GW monitor, it's ten years old and I love the display hence I don't want to replace it (can't really afford to either).

Some months ago it started to exhibit the well known power on issues so I replaced all of the electrolytics (except for the 100uf 450v) with new, high quality, 105 degree electrolytics. Suffice to say that a number of the old caps were bulging, but not leaking.

All was well for a few months but power on problems have returned, a little different this time though as now after a few hours switched off and then powered on, the overall display will be dim but is particularly dark on the left side; it will rapidly flicker then blank out completely after a few seconds. If I leave it like this for a few minutes (blank display, power still on) then power off and on again all is well. So there's a warm up required.

I've taken it apart again, checked the ESR of all of the new caps (they are fine and physically they look fine too) and the old 100uf 450v electrolytic also has good ESR. Not sure if it's worth replacing that (I'd need to order one).

Any thoughts please as to the cause of this latest fault? (note: this only started a few days ago).

Thanks

Edit: Here's a photo of the board that I found online:

http://www.ccfloffer.com/bookpic/01/2232BW_Power_Board_IP-45130B.jpg

Model no: IP-45130B

I'm tempted just to buy a new board from China, but is it possible that the power board itself isn't at fault?

[Armadillo]

Use a magnifying glass, check for poor/dried/cold solder joints.
I suspect the old capacitors may have leaked and caused some broken traces. Just my suspect only. So you may use a multimeter on continuity mode to trace it out, including the vias for break in continuity.

 

[Toasty]

Backlights / CCFLs

ccflwarehouse.com is a source I use.

You'll need the exact length & diameter to replace them all.  Work can be tedious and frustrating.  Bulbs are easily snapped/broken.

You may also consider a complete LCD replacement screen assembly.

T

[SolderSucker]

Use a magnifying glass, check for poor/dried/cold solder joints.
I suspect the old capacitors may have leaked and caused some broken traces. Just my suspect only. So you may use a multimeter on continuity mode to trace it out, including the vias for break in continuity.

 

There were definitely no leaks from the old caps, they were just bulging at the top with no leakage at all.

Good point about dry joints, I'll check again.

[SolderSucker]

Backlights / CCFLs

ccflwarehouse.com is a source I use.

You'll need the exact length & diameter to replace them all.  Work can be tedious and frustrating.  Bulbs are easily snapped/broken.

You may also consider a complete LCD replacement screen assembly.

T

Interesting, I hadn't thought of that. But why would all those on the left fail in a more obvious manner when cold?

[gnif]

LCD backlight drivers are natorious for driver mosfet failures... either intermittant (as in your case) or complete. Usually the metal film capacitor next/near it dies along with it. I have repaired many LCD monitors simply by replacing the driver mosfets and caps.

[Toasty]

It's typically the positive end and in my experience it frequently seems to happen there.  If you open it up, you'll see that end is darker in color.  Just as fluorescent lamps do when they fail.

You enjoyed a long life out of that monitor.  Personally, I'd invest in a newer and bigger model.  Just my 2¢ 

T

[SolderSucker]

LCD backlight drivers are natorious for driver mosfet failures... either intermittant (as in your case) or complete. Usually the metal film capacitor next/near it dies along with it. I have repaired many LCD monitors simply by replacing the driver mosfets and caps.

So in this photo:

http://www.ccfloffer.com/bookpic/01/2232BW_Power_Board_IP-45130B.jpg

Which parts need replacing?

[SolderSucker]

It's typically the positive end and in my experience it frequently seems to happen there.  If you open it up, you'll see that end is darker in color.  Just as fluorescent lamps do when they fail.

You enjoyed a long life out of that monitor.  Personally, I'd invest in a newer and bigger model.  Just my 2¢ 

T

I know, but I hate throwing things out when they can be economically repaired.

[Toasty]

I too am a believer in that. BUT, there comes a time to say "See ya, old friend. Glad we spent some time together."

Your looking at ~$50 for parts and your time.  The learning curve & the "crap, they don't bend..." scenario.

T

[gnif]

LCD backlight drivers are natorious for driver mosfet failures... either intermittant (as in your case) or complete. Usually the metal film capacitor next/near it dies along with it. I have repaired many LCD monitors simply by replacing the driver mosfets and caps.

So in this photo:

http://www.ccfloffer.com/bookpic/01/2232BW_Power_Board_IP-45130B.jpg

Which parts need replacing?

Can't see them there, its a rarther small/simple one in comparison to the ones I have dealt with. They might be surface mount on the back, but I doubt it.

[SolderSucker]

LCD backlight drivers are natorious for driver mosfet failures... either intermittant (as in your case) or complete. Usually the metal film capacitor next/near it dies along with it. I have repaired many LCD monitors simply by replacing the driver mosfets and caps.

So in this photo:

http://www.ccfloffer.com/bookpic/01/2232BW_Power_Board_IP-45130B.jpg

Which parts need replacing?

Can't see them there, its a rarther small/simple one in comparison to the ones I have dealt with. They might be surface mount on the back, but I doubt it.

There is another PCB in the monitor with surface mounted electrolytics and other components, I guess the Mosfet and is on that?

Edit: in fact, the other board inside the monitor is of course the main driver board, here's one:

http://www.ccfloffer.com/bookpic/01/Driver_Board_BN41-00890A.jpg

Which part on that could be causing backlighting issues?

[gnif]

LCD backlight drivers are natorious for driver mosfet failures... either intermittant (as in your case) or complete. Usually the metal film capacitor next/near it dies along with it. I have repaired many LCD monitors simply by replacing the driver mosfets and caps.

So in this photo:

http://www.ccfloffer.com/bookpic/01/2232BW_Power_Board_IP-45130B.jpg

Which parts need replacing?

Can't see them there, its a rarther small/simple one in comparison to the ones I have dealt with. They might be surface mount on the back, but I doubt it.

There is another PCB in the monitor with surface mounted electrolytics and other components, I guess the Mosfet and is on that?

Edit: in fact, the other board inside the monitor is of course the main board, here's one on Ebay:

http://www.ebay.co.uk/itm/Samsung-BN91-01772T-BN41-00890A-Main-Board-/361401115052

Which part on that could be causing backlighting issues?

Please show a photo of the back of the power board.

[SolderSucker]

LCD backlight drivers are natorious for driver mosfet failures... either intermittant (as in your case) or complete. Usually the metal film capacitor next/near it dies along with it. I have repaired many LCD monitors simply by replacing the driver mosfets and caps.

So in this photo:

http://www.ccfloffer.com/bookpic/01/2232BW_Power_Board_IP-45130B.jpg

Which parts need replacing?

Can't see them there, its a rarther small/simple one in comparison to the ones I have dealt with. They might be surface mount on the back, but I doubt it.

There is another PCB in the monitor with surface mounted electrolytics and other components, I guess the Mosfet and is on that?

Edit: in fact, the other board inside the monitor is of course the main board, here's one on Ebay:

http://www.ebay.co.uk/itm/Samsung-BN91-01772T-BN41-00890A-Main-Board-/361401115052

Which part on that could be causing backlighting issues?

Please show a photo of the back of the power board.

Do you mean my own power board or any one of that model number? If you're wondering if there are any components on the back then, as I recall, there aren't.

[gnif]

Do you mean my own power board or any one of that model number? If you're wondering if there are any components on the back then, as I recall, there aren't.

You are not going to get much help if you do not provide the basic information needed to be assisted. The power supply board, the back of which will contain surface mount parts, for example a quick google shows this:

https://picclick.com/Power-Board-IP-45130B-BN44-00127U-For-SAMSUNG-2232BW-Brand-260933249365.html

The thrid picture clearly shows some surface mount components on the back of the unit. Please post a complete picture of the back of the PCB.

[SolderSucker]

I'm afraid that I don't have the means to take a digital photograph as my digital camera is faulty (something else that needs repairing or replacing when I can afford it).

However, how about the photo of the rear of the PCB in this auction, does that help:

http://www.ebay.com/itm/New-Power-Board-IP-45130B-BN44-00127U-For-SAMSUNG-2232BW-A011-/231410588330

Zooming in on it doesn't reveal the chip markings but maybe it's good enough?

[gnif]

Yes, that helps somewhat. See attached, those two chips are the driving mosfets that drive the backlighting transformers, one or both may be falting as they get warm, it is the most common cause of backlight failure in monitors like this.

[SolderSucker]

Thanks very much. You mention about one or both mosfets failing when they get warm but it's when the monitor is cold that the problem occurs. Presumably they could still be at fault of course.

Edit: I've just found the service manual for the 2232BW (mine is the GW but they share the same boards), it can be downloaded here:

https://www.electronica-pt.com/esquema/monitores/samsung-esquemas-monitor/samsung-2032bw-2232bw-lcd-monitor-26187/

[SolderSucker]

@gnif - I've had the back off the monitor again and checked what is engraved on those two chips, which is as follows:

SIM8309
77330

(both are the same)

Where would you recommend that I buy replacement chips please, and are there any more modern equivalents which I could perhaps more easily source? I'm in the UK so a UK supplier is preferred but I have a feeling I'm going to have to get some from China.

Thanks

[Rasz]

STM8309
$2 for 2-5 with free shipping on ebay
but it does sound like dying ccfls, on the other hand $2 is a good price for a long shot

[SolderSucker]

Thanks, I'll take a look.

[Armadillo]

It doesn't seems like the protection circuits came into play here and on all 2 CCFL at the same time ?
ehm..... Agree with the long shot but should continue to look further.

Edit: That mosfets can be checked with multimeter.

[Rasz]

can you reliably check rdson in milliohm range of a mosfet with a multimeter? it doesnt sound like those transistors are dead, but they might be dying/cooked.

[Armadillo]

can you reliably check rdson in milliohm range of a mosfet with a multimeter? it doesnt sound like those transistors are dead, but they might be dying/cooked.

Maybe lost a few watts, gets a bit warmer......
Sure don't fits OP description of problem when cold.

But never mind ..... try the long shot.... plug and play always the easiest and fastest.