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Louie
Louie, Technician
Category: TV
Satisfied Customers: 11432
Experience:  25+ yrs. experience in the field and 5+ yrs. online, down to component level.
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I have a Samsung monitor 2433LW with a problem. Actually it

Customer Question

Hello I have a Samsung monitor 2433LW with a problem. Actually it seems to work perfect. But after a while (some times after a few seconds, sometimes after half anhour or such). the screen turns blank, few seconds later picture returns. This repeats irregulary.
On occasion also the power LED will turn off and on almost in sync with the screen.
The first described problem can be simulated by pressing the "enter" button (when not in menu mode). Doing that will result in exactly the same behaviour.
The second described problem can be simulataed by pressing the power button. (So in this case it looks as if the power button is pressed to switch off, and pressed again to switch the unit on. All by itself.)
Any tips or suggestions?
Thanks in advance.
Best regards,
Maarten Dekkers
Submitted: 18 days ago.
Category: TV
Expert:  Louie replied 18 days ago.

Hi Maarten and welcome to the site, I’m Louie. Sorry you had to wait awhile but I’ll do my best to help.

Initially, let's review, try, check the basics (if have not been done);

  • determine if the issue is commonly exhibited with DVI and VGA video feed;
  • performa RESET;
  • monitor the consistency of the output voltages of the power supply board;
  • disconnect the backlight connectors 1-at a -time and observe if symptom would persist.
Customer: replied 17 days ago.
Hi Louie,
Thanks for your reaction. Yes, I tried using the VGA and DVI interface, both have the same problem. (I 've been trying to repair for about three weeks now...) At a certain point when I disassembled the unit, the problem (with also the LED going off and on) was very frequent (about every 20 seconds or so), at that moment I measured the power rails on the IP board (inverter / power) by using an oscilloscope. All voltages were 'perfectly' stable. Also measured the 1.8V and 3.3V on the logic board. No dip or instability there too.
To make sure it was no problem with the EDID data I found the .bin files on a webpage and reflashed both EEPROMs. I also found a .bin file with the main program and reflashed the flashrom. All to no avail! (at least it is reset to the manufacturer defaults).
As the problem looked like using the power button, at a certain point I removed the keyboard: problem disappeared!
As you perhaps know the keyboard (6 keys) uses two ADC channels on the microcontroller. Measuring did not reveal anything problem to me but I decided to resolder the interfacing circuits around the ADC channels and tested it for some hours. Seemed ok.
I put it back together and started testing at my normal PC. For about two evenings it worked ok. Then it started 'blinking' again (now the problem was the "enter button" type.) That was last wednessday.
Today before I posted my question I took it apart again. 'Too bad' the problem didnot show up. So that makes measuring very hard...
Please note that when the screen turns blank, the backlight is still on! (I even did try with setting the brightness very dim, no difference.)
Of course I searched the internet before and it seems that this problem is not very common...Maarten
Expert:  Louie replied 17 days ago.

Hi again Marteen,

Apologies for the delay as I am currently mobile with sluggish Internet if at all.

Bear with me. I would look into the Service Manual soon as I am back at my workstation.

Customer: replied 17 days ago.
Ok, take your time. I'm already struggling with for some time now no rush.
Expert:  Louie replied 16 days ago.

Hi again,

Do you have a copy of the Service Manual particularly the Troubleshooting section?

Customer: replied 16 days ago.
Hi Louie, I do have a chinese version. It is too big to attach it completely, but I added the trouble shooting part. Perhaps you can find the complete version on the internet (it is however not the same model (P2250W, chassis: LLR22KS) but the logic board is the same: BN41-01172B))
Too bad no complete diagram of the electronics is included...
Expert:  Louie replied 16 days ago.

That would appear to be Chapter 4 Troubleshooting and yes even the English version has limited schematics.

Would this English version be of help ?

Customer: replied 16 days ago.
Not really I'm afraid. I asked someone to translate some keywords and it seems that the "trouble to be shooted" is only when no power and / or no picture at all is the problem. Nothing about my intermittently problems...
Expert:  Louie replied 16 days ago.

This may be crucial, "...keyboard...resolder...about two evenings it worked ok..." Since it is intermittent, might it be switch bounce; i.e. any of the keys acting on its own every now and then. This may be caused by temperature, humidity, dust, vibrations.

Customer: replied 16 days ago.
Before I did try to tap the keyboard gently, no change.
Later this afternoon or evening, I will open the unit again to see / test temperature by using a hot air blower and cold spray. I'll let you know.
Expert:  Louie replied 16 days ago.

Yes please and would look forward to an update Maarten when able.

Customer: replied 15 days ago.
Hi Louie,
Heating or cooling didn't seem to trigger the fault. Although now the backlight is failing sometimes. Before the screen went off but the backlight stayed on. Now the backlight switches off and, as far as I can tell, the picture remains.... (without keyboard I should add)
.. gives me a headache!
Expert:  Louie replied 14 days ago.

Hi again Maarten,

Bear with me as mobile again / field service.

Customer: replied 10 days ago.
Hi Louie, I guess you ran out of ideas too?
Expert:  Louie replied 10 days ago.

Yes Marteen and time.

Still, let me re-open the question in the hope that another member of the site can provide an alternate approach to your concern.

Thank you for your kind understanding and patience.