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    #81
    Re: Samsung SyncMaster 2493HM black screen with power

    solved case that worked for me after all procedures above failed in my case:
    my psu is a BN44-00195A model 245B2 (slightly different part numberingfrom schematics above)
    symptom was:
    a black screen with blue power light steady on.
    5,2V standby power was ok, primary PFC voltage was ok (380V for my european 220V input monitor). but the backlight 24V was not there ...(5.3V was not their either since it is a byproduct of the main 24V output...).

    what I did:
    A) replaced most polarized cap though all my caps looked ok (no bulging top)---> still black screen
    B) checked for the yellow glue becoming conductive, clean up a couple of components ---> still black screen (no 24V out)
    C) checked the operation of the MC33067P ICM801
    pin 14 was always high and pin 12 alway low...check the oscillator (pin 2 ) and their was no oscillations there, so I started looking at reasons for not startup of the IC in the datasheet...
    pin15 12V was ok (power supply)
    pin 8 non inverting output of error was 5.1V =(ref voltage of the IC) --> force max oscillator frequency in principle...

    pin 10 fault input was low when I mesured it...so in principle all was ok , no fault detected ...
    By reading the datasheet of the IC , I noticed that if there was a pulse greater than 1v on the fault pin the IC would lock itself to prevent serious damage and remain in that state until power is removed...
    It was a long shot but I decided to connect my DSO (! use double 12V-220V AC 3A transformers back to back on the 220V ac input to allow the whole supply to float and prevent to blast my scope inputs!!!! Ov of the scope is connected to earth in principle...)
    So, i measured (captured) the Pin 10 level as I flipped on the power switch of the PSU and I noticed a tiny 10ms 1.1V pulse on the fault line after 200ms then the line was perfectly below the 1V threshold of the fault input pin (pin10)...I was nearing the solution.
    There are two separate circuits tha can trigger a fault condition on pin 10:
    1)- the overvoltage monitoring circuit via opto PC802S on the schematics(PC804S on my PSU model)
    2) the "feedback/monitoring circuit" from the primary of the TM801S transformer (DM805-CM809-RM815 on the scematics)

    on the overvoltage monitoring circuit, I disconnected the 0 ohm resistor (it not on the schematics, but on the PCB is is easy to find by following the tracks)
    between the PC802S opto led cathode and the LMBT2222 transistor to desactivate that circuit and measured again the power up sequence on pin 10 ---> the 10ms pulse high was still there....
    Then,
    I checked carefully feedback components from the the primary of TM801S transformer and noticed nothing abnormal at first, then I notice some of that yellow hardened glue on the 47pF 1KV capacitor (CM809 on the schematics) in the feedback circuit. That glue was covering both legs of the capa!!! It was a long shot but I decided to desolder the capa and clean it up as nice as possible without breaking it...soldered it back...and it WORKED! The MC3306P was oscillating nicely and the 24V was back, I reconnected the 0 ohm resistor of the other monitoring circuit and all was OK.
    My 2493HM monitor is back to life and so far it as been working perfectly again...

    So my advice is CHECK the Yellow glue on all critical components and remove it if you can!!!

    Now I know that PSU quite well since I have been working on it for a complete day or so....Since I have two of those monitors I am ready for the second one when it fails (hope not but...)
    McEugene is online now Report Post

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      #82
      Re: Samsung SyncMaster 2493HM black screen with power

      My issue matches the original issue. Samsung Syncmaster 2493HM. It powers on (Blue LED on) & my laptop recognizes it (2nd monitor = Samsung Syncmaster & allows me to scroll off of my laptop screen (extend mode) as though extending to the monitor). However, the screen of my 2493HM is black. I read a lot of these posts & did some troubleshooting ahead of time, but have not replaced any parts yet (actually, I did replace 1 cap). I'm sure the issue is on the inverter board. No deformed caps.

      BTW, this happened after a lightning strike. A fluorescent light also quit & I had to replace the board inside, not just the bulb.

      So far, on the inverter board, I've checked the power semiconductors (TO220s, including FET body diodes), a few axial diodes & the optocouplers & they all show the diode drop. I checked the main two fuses (someone mentioned another fuse... don't know where that is... maybe not on the inverter). I get 169V from + to - on the rectifier (124VAC in). I measured the electrolytic caps, all seemed to have reasonable values (value correct or above, some in parallel) except 1... the 10uF 50V cap next to the DONG YANG name, couldn't get a reading (DMM shows open lead), replaced with 10uF 100V 105C Nichicon cap... measured 10uF out of circuit, still open lead in circuit. Touched up a few ugly joints in the process.

      On the white right angle connectors (opposite side of AC input, 2 on one side, 1 on the other), I am getting 0V on most every pin, including 24V & 5.4V pins. I am, however, getting 5.25V on the standby pin.

      Questions:
      1) Does anyone have some sort of schematic for the inverter board?
      2) Looks like the standby supply has a separate transformer, but shares the 82uF 450V cap on the primary side... Seems like the issue is going to be on the secondary side of the large flyback... Any known issues on Main supply (24V) secondary?
      3) Can anyone else read the 10uF 50V cap next to the DONG YANG name (in circuit)?
      4) There is a slight rattle when I give the board a little shake... I've heard this before on power electronics, assume it's something in magnetics or input connector... Anyone else hear this? Sounds like a screw tapping against plastic... standard rattle. Don't think it's an issue, but figured I'd mention it.

      Thanks lots,

      Mike

      Comment


        #83
        Re: Samsung SyncMaster 2493HM black screen with power

        What the board number on this version of the monitor? BNXX-XXXXX? Pictures of your boards will help, what ever the problem is, the glues must be removed for sure.
        Last edited by budm; 09-19-2013, 10:17 PM.
        Never stop learning
        Basic LCD TV and Monitor troubleshooting guides.
        http://www.badcaps.net/forum/showthr...956#post305956

        Voltage Regulator (LDO) testing:
        http://www.badcaps.net/forum/showthr...999#post300999

        Inverter testing using old CFL:
        http://www.badcaps.net/forum/showthr...er+testing+cfl

        Tear down pictures : Hit the ">" Show Albums and stories" on the left side
        http://s807.photobucket.com/user/budm/library/

        TV Factory reset codes listing:
        http://www.badcaps.net/forum/showthread.php?t=24809

        Comment


          #84
          Re: Samsung SyncMaster 2493HM black screen with power

          BN44-00195A. I'll get a pic of it up soon. Is the glue conductive some how? There is a blue cap with both leads covered by the same blob of glue, but I can still read the correct value...

          Comment


            #85
            Re: Samsung SyncMaster 2493HM black screen with power

            Somebody gave me also same lcd monitor. Just dark screen. There was only for logic board +5v. When you pres power button main supply +5v and 24v was coming and going.. I flow all the advices in this posts. I cleaned all slicon glues, changed all caps. But i had still same problem. Finally i found ic MC33067P pin10 flow this pin going to ZDTM801=TL431 ref ic. I changed 24v came. Now my monitor work perfect. Thanks for all hints.

            Comment


              #86
              Re: Samsung SyncMaster 2493HM black screen with power

              I have one of these monitors that i repaired,i did 3 things don't know for sure which was the one that brought it to live, re-soldered all components and joints in power supply,removed 47pF 1KV capacitor (CM809] cleaned hard glue and scraped the legs,and re-soldered it back,removed all the hard glues on power supply.

              Comment


                #87
                Re: Samsung SyncMaster 2493HM black screen with power

                Hey everyone!

                I had the same problem with my 7 year old Samsung SyncMaster 2493HM a few days ago.
                A long time (maybe a year or more) before the display went completely black this week I noticed it was irregularly going on and off for about 2 seconds.
                And then: the blue LED was still on but the backlight was dead.

                Here is what I've done to solve this issue:

                After reading and searching a lot on this forum, YouTube (VERY NICE SOURCE) and on the whole internet I came to the conclusion that I should measure the voltages on the power supply board and check all the capacitors for escaping electrolyte and bulges.
                All capacitors looked good on the outside but of course that does not indicate that they are working properly.
                The measurement showed that the inverter board and the logic board (24V connector and 5V connector) were not supplied with any voltages (0V instead of 24V and ~0.25V instead of 5V) by the power supply board.
                My last chance now was to replace the most likely damaged capacitors on the board but since I do not have any meter for capacities I searched for a list of all matching capacitors:

                Code:
                2x 10uF  50V
                1x 2,2uF  50V
                3x 47uF  50V
                1x 22uF  50V
                2x 1000uF 35V
                1x 470uF  35V
                1x 2200uF 10V (I took 16V!!)
                1x 1000uF 10V (I took 16V!!)
                
                I took PANASONIC capacitors only.
                Notice that I decided to take capacitors with 16V proof voltage instead of 10V for the last two in the list, because I've read that these two are intentionally undersized.

                In a thread on this forum someone mentioned that the two yellow SamYoung NXH 470uF capacitors on the inverter board are also not very solid and so I decided to replace them, too:

                Code:
                2x 470uF 35V
                And what can I say?
                I unsolded the old ones, made a list of all labels and the corresponding capacitors on the board incl. capacity and voltage and replaced all of them with the new PANASONIC ones.

                The moment of truth: IT WORKS
                No flashing, quick startup.

                I paid ~17€ including postage and spent a few hours with disassambling and soldering (because I'm a newbie lol).

                Well worth it!
                Thank you everyone!
                Last edited by wolle1811; 07-01-2016, 10:28 AM.

                Comment


                  #88
                  Re: Samsung SyncMaster 2493HM black screen with power

                  You're very welcome, said in the name of those whose knowledge helped you.

                  The best way to pay back is by helping others, for sure.
                  stay classy

                  Comment


                    #89
                    Re: Samsung SyncMaster 2493HM black screen with power

                    Wow. Took the monitor apart, looked at the power supply board. Didn't notice any damaged, swollen capacitors, or any brown looking glue. I could spend evenings chasing this down that I'd rather spend doing other stuff. And damn that glue is hard, what a pain it is to remove all that crap from the component leads and all. A 10 year old monitor doesn't owe me too much. I'm going to keep my eye out for a sale on a new one and move on.

                    Comment


                      #90
                      Re: Samsung SyncMaster 2493HM black screen with power

                      Absolutely newbie to the world of capacitors, but seeing as every single electronic device now uses them, I am compeled to learn about how to diagnose them as failing components when my devices stop working !!

                      I have the usual solid blue 'power on' light and black screen symptoms on three of my failed Samsung 2493HM monitors. Rather than simply discard them to fill some landfill site somewhere, I decided to try and fix them and stand up to the corporate directive to constantly part us with our hard earned money

                      Also the fact that the Samsung 2493HM is one of the few monitors that is 1920x1200 (16:10 Aspect Ratio) with a good build (apart from the caps, of course, which seem to be a common problem with all Samsung screens).

                      I took the lead from wolle1811 to replace all the existing caps with better quality parts, but Panasonic do so many different types of capacitors !!

                      As I am based in the UK, I am looking at two different local suppliers to furnish me with the required caps as recommended by wolle1811:

                      http://www.mouser.co.uk
                      http://uk.farnell.com

                      I would be grateful for any advise on factors (and any other parameters other than Voltage, physical size and Capacitance) I should take into consideration when ordering the 'like for like' panasonic caps e.g ESR, Series types, Hybrids etc.

                      Thanks in Advance.

                      Comment


                        #91
                        Re: Samsung SyncMaster 2493HM black screen with power

                        Originally posted by mocamanica View Post
                        Absolutely newbie to the world of capacitors, but seeing as every single electronic device now uses them, I am compeled to learn about how to diagnose them as failing components when my devices stop working !!

                        I have the usual solid blue 'power on' light and black screen symptoms on three of my failed Samsung 2493HM monitors. Rather than simply discard them to fill some landfill site somewhere, I decided to try and fix them and stand up to the corporate directive to constantly part us with our hard earned money

                        Also the fact that the Samsung 2493HM is one of the few monitors that is 1920x1200 (16:10 Aspect Ratio) with a good build (apart from the caps, of course, which seem to be a common problem with all Samsung screens).

                        I took the lead from wolle1811 to replace all the existing caps with better quality parts, but Panasonic do so many different types of capacitors !!

                        As I am based in the UK, I am looking at two different local suppliers to furnish me with the required caps as recommended by wolle1811:

                        http://www.mouser.co.uk
                        http://uk.farnell.com

                        I would be grateful for any advise on factors (and any other parameters other than Voltage, physical size and Capacitance) I should take into consideration when ordering the 'like for like' panasonic caps e.g ESR, Series types, Hybrids etc.

                        Thanks in Advance.
                        Hello everyone!
                        After years of work my Samsung 2493HM monitor has decided not to work anymore (Blue LED off etc.) but since I'm sorry to throw it away, given the performance, I came across this beautiful forum! I followed the instructions: I removed the yellow glue where I could, replaced a part of electrolytics and ... the famous 47pF1000V capacitor I replaced it (but it looked good) with a MULTILAYER 47pF I had ... 100V though! On, it seemed to work fine but after a while he started to smoke something! Reopened, found a 2 / 3W vertical resistor near a 2.2nF capacitor, split in half and completely burned out. Replaced with the one I had, hoping to guess the value: maybe 27 Ohm, it seems, I put a 22 Ohm 3W in it. Perfect! It worked ... but only for a few days! I know the post is very old, but maybe there is still someone who can give me suggestions ... I also found the original Samsung SERVICE MANUAL, but those components are not even listed ... Thanks to anyone can me help, in advance.

                        Comment


                          #92
                          Re: Samsung SyncMaster 2493HM black screen with power

                          Originally posted by McEugene View Post
                          solved case that worked for me after all procedures above failed in my case:
                          my psu is a BN44-00195A model 245B2 (slightly different part numberingfrom schematics above)
                          symptom was:
                          a black screen with blue power light steady on.
                          5,2V standby power was ok, primary PFC voltage was ok (380V for my european 220V input monitor). but the backlight 24V was not there ...(5.3V was not their either since it is a byproduct of the main 24V output...).

                          ...snip...

                          So my advice is CHECK the Yellow glue on all critical components and remove it if you can!!!

                          Now I know that PSU quite well since I have been working on it for a complete day or so....Since I have two of those monitors I am ready for the second one when it fails (hope not but...)
                          McEugene, My PSU is identical to yours and I have the same symptom.

                          I tested resistance of the yellow goo and it was obvious that where it had turned brown and discoloured (heat?) that the resistance was low (it was easy to measure < 500kΩ). On the bright yellow glue, resistance still appears high (OL on meter, 20M range).

                          I removed as much of the browned goo as I could. It smothered a few capacitors and other components as in your case. However, after that cleanup there was no change in symptoms.

                          Were you doing any testing out of circuit, or were your voltage measurements etc with the inverter board in place in the system? I know that SMPS often do not like running unloaded.

                          I also made a rough in-circuit measurement of the smoothing caps near the 24V and 5V sections - and they looked okay. No sign of bulging, leaking etc.

                          Looks like this isn't going to be an easy fix
                          Last edited by qu1j0t3; 07-11-2021, 03:04 PM.

                          Comment


                            #93
                            Re: Samsung SyncMaster 2493HM black screen with power

                            I have (more than one) SM245B monitor but I'm in opinion that they use same power boards, either BN44-00173A or BN44-00195A.
                            I currently have only board BN44-00173A in working monitors. I did a fix for BN44-00195A, it worked perhaps a day or two.

                            My experience with these boards (how to fix).

                            For BN44-00173A:

                            In most cases the three 68ohm resistors, replace with 2 or 3 watt ones.
                            Check also other resistors near power diodes and mosfets, I remember one of those was broken in one case.
                            Also replace at least all electrolytic caps near SI-8008HFE.


                            For BN44-00195A:

                            Check QT851 SMD transistor and SI-8008HFE regulator near trafo.
                            I remember having both or one of them broken.
                            Of course some electrolytic caps replacement recommended, at least those near SI-8008HFE.

                            Some help in this old forum post.
                            Last edited by euromatlox; 08-10-2021, 02:47 AM.

                            Comment


                              #94
                              Re: Samsung SyncMaster 2493HM black screen with power

                              Originally posted by vedo35 View Post
                              Somebody gave me also same lcd monitor. Just dark screen. There was only for logic board +5v. When you pres power button main supply +5v and 24v was coming and going.. I flow all the advices in this posts. I cleaned all slicon glues, changed all caps. But i had still same problem. Finally i found ic MC33067P pin10 flow this pin going to ZDTM801=TL431 ref ic. I changed 24v came. Now my monitor work perfect. Thanks for all hints.
                              Well this is part of what fixed my problem combined with the other advice. I had changed the bulged cap like everyone else. I cleaned all the glue up and I had this problem where it would work sometimes and then just go black and make this electric purring noise. I left it in storage for 7 years and I finally decided to take a final look and I found a transistor (Don't know which one because the print came off with the glue from the board, but the chip itself was labeled D526-Y) looked like it had sunken in the board further than everything else indicating excessive heat. So i pulled it and low and behold... there was still glue connecting the pins underneath it and it was burnt! So I tested it (good) and cleaned it up, put it back in and sadly was back to just a black screen. But I noticed it didn't come on anymore which had me thinking it was jammed in error. Well, I reflowed pin10 of MC33067P and BAM! unit is finally operational! Thanks for the advice everyone! I miss nice electronics, everything is garbage these days.

                              Comment


                                #95
                                Re: Samsung SyncMaster 2493HM black screen with power

                                If it acts up again, try replacing CM806 (10µf/50v) Also CB806 and CP811 (47µf/50v), these caps are on the ic's VCC line and fail often.

                                Comment


                                  #96
                                  Re: Samsung SyncMaster 2493HM black screen with power

                                  Originally posted by R_J View Post
                                  If it acts up again, try replacing CM806 (10µf/50v) Also CB806 and CP811 (47µf/50v), these caps are on the ic's VCC line and fail often.
                                  Thanks, I'll keep that in mind. I did pull CB809 to remove some glue and it tested good on capacitance and ESR so I put it back in. It seems like it's more the glue that was the main culprit in most cases. When I have time I will take an image of my board BN44-00195A or a stock one and circle the area with the transistor to make it easier for others. The glue was in other places too though I spent quite some time cleaning it up. So silly the whole product was ruined by putting glue (which is serving no purpose other than breaking the product) randomly on spots that I assume are likely to heat up. Also might be good to reflow pin 10 MC33067P.

                                  Attached Files
                                  Last edited by SMDFlea; 08-04-2022, 10:48 AM. Reason: Added image to badcaps from dropbox

                                  Comment


                                    #97
                                    Re: Samsung SyncMaster 2493HM black screen with power

                                    So the image in the previous post we have a pic of the board and the green circles highlight the bulged cap that was replaced, the transistor that was causing the problem with glue hidden underneath arcing the legs together and pin 10 to be reflowed. All of the red arrow are glue areas to be carefully removed as they have potential to arc as well. Hope it helps somebody!

                                    Actually This is the correct picture, I realized I labeled pin 10 incorrectly as I was looking at it upside down.



                                    https://www.dropbox.com/s/750vyaxdo5...N44-00195A.jpg
                                    Last edited by joshmonger; 08-04-2022, 11:35 AM. Reason: Incorrect picture

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