Need help on Samsung Syncmaster 153V

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  • mikey5791
    Badcaps Veteran
    • Dec 2014
    • 515
    • Malaysia

    #1

    Need help on Samsung Syncmaster 153V

    A friend sent me this old Samsung Syncmaster 153V LCD monitor to repair. The problem is power board no power, completely dead no light whatsoever. the power switch led no light during testing or after switched on main.

    I had some basic skills in repairing dead monitor with a soldering iron,solder pump,a digital multimeter (DMM), and a digital capacitor meter. After opening up the case, I see no bulging caps or burnt marks on the power supply board and try search online for a service manual/schematic but none found.

    I ghetto work a 60W Light bulb tester(series current limiter) as per image 1644,I resolder the transformer (image 1629), and some 3 pieces 470uF25V caps at position C665,C662 &C661, also remove a 330uf25V cap at C17 and the 4 small caps (each is 47uF25V). Tested using my capacitor meter & Replaced those 470uF that reads less than 10% off scale (like 425uF)..... surprisingly the 4 small caps (47uF25V) in the center
    still reads within range, so i didn't replaced them.

    Tested continuity of transformer with an analogue multimeter, it shows continuity; so i put it back.

    Switched on 220AC main without connecting to LCD panel or vga board, the light bulb light on a second then lights off, followed by flickering(oscillating siren like) light bulb. This indicate somewhere there is still a fault. Also I noticed some buzzing/hissing noise near the yellow transformer area.I desolder the rectifier diode STPR10, off circuit tested ok, but anyway I replaced with STPR1020CT. Also i replaced new 470UF 25V & 1000UF 25V caps at C661&C441 just in front of the new diode.

    Did some volt test on primary bridge rectifier=232vAC, main cap=317vDC
    There is power from primary output.

    On secondary side,voltage test by red DMM probe to diode cathode & black probe to chassis on diode near yellow trans(transformer)=0vDC, same probe testing on diode D320=-101vDC (why negative? strange) On diode D440 on heatsink(SBL1040CT)middle pins=0 vDC(zero volt)
    Is the result clearly mean secondary side no power output ? somewhere along the line there is a fault.


    How do I check output DC voltage on the white connector(image 1685) ? Do i put positive probe to third wire from right side marked +5v? then negative probe to chassis ?

    The light bulb in series still lit brightly flickering.
    Something else is shorted.

    Anyone pls help diagnose/solve this no power from secondary output or list down voltage test point.
    Attached Files
  • TechGeek
    Computer Geek
    • Jan 2015
    • 2254
    • USA

    #2
    Re: Need help on Samsung Syncmaster 153V

    Was the fuse blown when you got it?
    Don't buy those $10 PSU "specials". They fail, and they have taken whole computers with them.

    My computer doubles as a space heater.

    Permanently Retired Systems:
    RIP Advantech UNO-3072LA (2008-2021) - Decommissioned and taken out of service permanently due to lack of software support for it. Not very likely to ever be recommissioned again.
    Asus Q550LF (Old main laptop, 2014-2022) - Decommissioned and stripped due to a myriad of problems, the main battery bloating being the final nail in the coffin.


    Kooky and Kool Systems
    - 1996 Power Macintosh 7200/120 + PC Compatibility Card - Under Restoration
    - 1993 Gateway 2000 80486DX/50 - Fully Operational/WIP
    - 2004 Athlon 64 Retro Gaming System - Indefinitely Parked
    - Main Workstation - Fully operational!

    sigpic

    Comment

    • CapLeaker
      Leaking Member
      • Dec 2014
      • 8146
      • Canada

      #3
      Re: Need help on Samsung Syncmaster 153V

      Sounds like you have no STBY voltage to begin with. Check if you get STBY voltage on the secondary.
      Last edited by CapLeaker; 04-23-2016, 02:37 PM.

      Comment

      • stj
        Great Sage 齊天大聖
        • Dec 2009
        • 31015
        • Albion

        #4
        Re: Need help on Samsung Syncmaster 153V

        firstly, you need to replace *all* the caps other than the mains filter.
        i dont care what your cap meter says.
        the pink looking ones are cooked, they are supposed to be light-blue and have changed colour from the heat!
        also the 4 small ones center right,
        one is the startup-cap and the sleeving has shrunk from the heat.
        probably because the stupid-fuck designer put it between a heatsink and transformer!

        i see you fitted a panasonic in there,
        it looks like silver on black.
        if that's an NHG series then it wont work in a psu - you need FR,FC,FM or FK series.
        NHG is not low-esr

        Comment

        • comptek
          Badcaps Veteran
          • Aug 2013
          • 606
          • uk

          #5
          Re: Need help on Samsung Syncmaster 153V

          whats the brown lump top of first pic on the diode to the left is it brown glue ?
          that may be an issue as it goes conductive

          Comment

          • mikey5791
            Badcaps Veteran
            • Dec 2014
            • 515
            • Malaysia

            #6
            Re: Need help on Samsung Syncmaster 153V

            TechGeek,

            The fuse is not blown, on continuity it tested ok(dial swing) with an analog meter. Now,I
            had soldered in a light bulb series as current limiter (img 1727) in place of the fuse.

            CapLeaker,

            How /where do I check if I have STBY voltage on the secondary ? Is that the cap near position U320 on img1629 (the small cap with brown glue like lump on diode which is between heatsink & transformer)?

            stj,

            Are you referring the startup cap which position U320 on img1629 (the small cap with brown glue like lump on diode which is between heatsink & transformer)? If possible, maybe can you mark the startupcap in red.
            I will try to source at local shop for the 4 small caps center right; and the Panasonic silver on black NHG series to either FR,FC,FM or FK series.

            comptek,

            I had scrapped off the brown lump glue like substance just in case it is conductive.


            Appreciate the replies and thanks so much for all the feedback and advice.

            Comment

            • CapLeaker
              Leaking Member
              • Dec 2014
              • 8146
              • Canada

              #7
              Re: Need help on Samsung Syncmaster 153V

              Measure all voltages on your picture #7 and post them with the pin out name.

              Comment

              • stj
                Great Sage 齊天大聖
                • Dec 2009
                • 31015
                • Albion

                #8
                Re: Need help on Samsung Syncmaster 153V

                see pic
                Attached Files

                Comment

                • mikey5791
                  Badcaps Veteran
                  • Dec 2014
                  • 515
                  • Malaysia

                  #9
                  Re: Need help on Samsung Syncmaster 153V

                  Hi Capleaker,

                  In earlier post,I had scrapped off the brown lump from the possibly startup
                  cap at C323. I switched on AC mains,the light bulb in series lit a second
                  then dims off; this time no flickering or hissing noise.Then I set DMM to DC,
                  black proe touching on metal chassis and red probe to each of the 9 pins on
                  img 1737,but sadly all pins read zero.(also no blue LED on power switch)

                  Out of curiousity, I replaced the old startup cap (Capxon 47UF50V) with a new
                  Maxcap 47UF50V) with same zero voltage reading on DC scale.
                  Where do we go from here? Hoping for your generous help to solve no power
                  issue and to have a learning experience.


                  Hi stj,

                  Due to workload, I have yet to find time to replace the 4 small caps in the
                  center right; and the Panasonic silver on black NHG series to either FR,FC,FM
                  or FK series.Is it still possible to detect STBY voltage without replacing
                  these caps?
                  Attached Files

                  Comment

                  • stj
                    Great Sage 齊天大聖
                    • Dec 2009
                    • 31015
                    • Albion

                    #10
                    Re: Need help on Samsung Syncmaster 153V

                    the 4 pink ones are for the backlight invertor, but the small ones on the right really need to be o.k. for standby to work

                    Comment

                    • mikey5791
                      Badcaps Veteran
                      • Dec 2014
                      • 515
                      • Malaysia

                      #11
                      Re: Need help on Samsung Syncmaster 153V

                      Hi stj,

                      Will find time to get the 4 pink small caps, they are Capxon 47UF25V.
                      Last night, I replaced the old startup cap (Capxon 47UF25V) with a new
                      Maxcap 47UF25V), scrapped off the black lump, then on DC voltage test the output still reads with same zero voltage reading on DC scale.(my test is on 9 pins pinout on img 1737 post #9.

                      Is this the only startup cap for the standby to work? Hoping for your kind advice.
                      Thank you.

                      Comment

                      • stj
                        Great Sage 齊天大聖
                        • Dec 2009
                        • 31015
                        • Albion

                        #12
                        Re: Need help on Samsung Syncmaster 153V

                        no, the small ones are all related to starting and running.
                        wtf is maxcap? that's probably worse than capxon.
                        cant you find any rubycons like YXF,YXG or YXJ, or some panasonic FC or FR?

                        Comment

                        • TechGeek
                          Computer Geek
                          • Jan 2015
                          • 2254
                          • USA

                          #13
                          Re: Need help on Samsung Syncmaster 153V

                          Originally posted by mikey5791
                          Hi stj,

                          Will find time to get the 4 pink small caps, they are Capxon 47UF25V.
                          Last night, I replaced the old startup cap (Capxon 47UF25V) with a new
                          Maxcap 47UF25V), scrapped off the black lump, then on DC voltage test the output still reads with same zero voltage reading on DC scale.(my test is on 9 pins pinout on img 1737 post #9.

                          Is this the only startup cap for the standby to work? Hoping for your kind advice.
                          Thank you.
                          Maxcap? PLEASE swap that out immediately.
                          Don't buy those $10 PSU "specials". They fail, and they have taken whole computers with them.

                          My computer doubles as a space heater.

                          Permanently Retired Systems:
                          RIP Advantech UNO-3072LA (2008-2021) - Decommissioned and taken out of service permanently due to lack of software support for it. Not very likely to ever be recommissioned again.
                          Asus Q550LF (Old main laptop, 2014-2022) - Decommissioned and stripped due to a myriad of problems, the main battery bloating being the final nail in the coffin.


                          Kooky and Kool Systems
                          - 1996 Power Macintosh 7200/120 + PC Compatibility Card - Under Restoration
                          - 1993 Gateway 2000 80486DX/50 - Fully Operational/WIP
                          - 2004 Athlon 64 Retro Gaming System - Indefinitely Parked
                          - Main Workstation - Fully operational!

                          sigpic

                          Comment

                          • mikey5791
                            Badcaps Veteran
                            • Dec 2014
                            • 515
                            • Malaysia

                            #14
                            Re: Need help on Samsung Syncmaster 153V

                            Hi stj & TechGeek,

                            Will swap out that Maxcap thing once I bought some better cap from local store.
                            hopefully any rubycons like YXF,YXG or YXJ, or some panasonic FC or FR will
                            do.

                            Many thanks for advice.

                            Comment

                            • mikey5791
                              Badcaps Veteran
                              • Dec 2014
                              • 515
                              • Malaysia

                              #15
                              Re: Need help on Samsung Syncmaster 153V

                              Hi stj & TechGeek,

                              On second thought, if I am unable to source for the startup cap (old one is Capxon 47UF 25V), is it ok to replace using a new cap rating of 470UF 25V?

                              On the 4 pink small caps, they are originally Capxon 47UF 25V as well, is it ok to
                              replace using a new cap rating of 470UF 25V or even much higher 1000UF 25V as our local store seldom sell such a low 47UF cap. Eager to know.

                              Comment

                              • Behemot
                                Badcaps Legend
                                • Dec 2009
                                • 4845
                                • CZ

                                #16
                                Re: Need help on Samsung Syncmaster 153V

                                The small (most likely ST) caps should be violet, I don't think they are THAT discolored. Who knows what sleeving crapxon uses, may be degrading by itself.

                                Anyway, do you know what voltage does it use for inverter? If it will be like up to 13.5 V you can easily use 16V caps. No need to keep the capacity, if you have 100uF caps, use those. If they are too tall, bend them flat.
                                Less jewellery, more gold into electrotech industry! Half of the computer problems is caused by bad contacts

                                Exclusive caps, meters and more!
                                Hardware Insights - power supply reviews and more!

                                Comment

                                • mikey5791
                                  Badcaps Veteran
                                  • Dec 2014
                                  • 515
                                  • Malaysia

                                  #17
                                  Re: Need help on Samsung Syncmaster 153V

                                  Since it is not easy to buy good quality small cap of those capacity in our part
                                  of the country, my friend said just scrapped it off. The dead monitor will be salvaged for other usable parts.

                                  Thanks all for help.

                                  Comment

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