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Princeton VL1812 Monitor

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    #21
    Re: Princeton VL1812 Monitor

    Originally posted by drewcam888
    When you say smps controller. I dont have a big ic like the schematic. The opto just drivers a 4 pin TO220 power switch that drives the transformer. So you want me to look at my TO220 IC?
    No!! You've misidentified the components. Take a picture of the back side of the board and attach it.

    PlainBill
    For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

    Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

    Comment

      #22
      Re: Princeton VL1812 Monitor

      Originally posted by drewcam888
      Th voltage goes from 8.6ish to 11.7ish then down to 8.6 in 2 seconds then back to 11.7 immediately and repeats over and over.
      Replace the little guy that PlainBill mentioned in post #13. I've seen many times oscillating voltages due to this small and often overlooked cap ....
      There are 10 kind of people in this world: those that understand binary, and those who don't.
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      Comment

        #23
        Re: Princeton VL1812 Monitor

        Attached is the photos of top and bottom. As you can see there are no components on the bottom.
        I will try and figure out which cap he is talking about in #13. I guess i don't know which cap to change because I don't really have this SMPS controller or at least I don't think I have what bill thinks I do.
        Attached Files
        Last edited by drewcam888; 10-15-2009, 09:48 AM.

        Comment

          #24
          Re: Princeton VL1812 Monitor

          Originally posted by drewcam888
          Attached is the photos of top and bottom. As you can see there are no components on the bottom.
          I will try and figure out which cap he is talking about in #13. I guess i don't know which cap to change because I don't really have this SMPS controller or at least I don't think I have what bill thinks I do.
          You're right. I've never seen this type of setup in an LCD monitor before. I801 is the SMPS controller and the power transistor combined into a single package. Please post the part number; that may lead to a data sheet, which will definitely help. In any case, I'd like to do a little research on it.

          As to the cap, it would be C808, the electrolytic cap just above the heat sink in the center of the board.

          PlainBill
          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

          Comment

            #25
            Re: Princeton VL1812 Monitor

            It is a KA1m0565r. I attached datasheet.
            Attached Files
            Last edited by drewcam888; 10-15-2009, 11:01 AM.

            Comment

              #26
              Re: Princeton VL1812 Monitor

              I replaced the C808. It was a 100uf 50v. I only had a 470uf 50v so it is in there now with no help. I just found some under rated caps also. Caps C817 and C814 are 10V when the voltage from the rectifier is sometimes current 11.7ish. I will fix that.
              Last edited by drewcam888; 10-15-2009, 11:07 AM.

              Comment

                #27
                Re: Princeton VL1812 Monitor

                Well maybe the voltage is right near 10V but it is way close to the rating. It may be higher when it actual starts to work right.

                Boy do I wish I could edit posts older than 10 minutes. It makes me post much more than needed. Has it always been that short.

                Comment

                  #28
                  Re: Princeton VL1812 Monitor

                  Here's an application note for the part.

                  PlainBill
                  For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                  Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                  Comment

                    #29
                    Re: Princeton VL1812 Monitor

                    So according to that Cfb matters. Even though it is a nonelectrolytic i might check it. The electrolytic I changed seems to matter to. It does it is Ccc on the Vcc pin of the switch. This is a great app note.
                    Last edited by drewcam888; 10-15-2009, 01:18 PM.

                    Comment

                      #30
                      Re: Princeton VL1812 Monitor

                      So since I have limited caps again. I placed two 47uf is parallel where the 100uf was. The voltage now does not vary nearly as much. So that helps. But isn't the entire solution. So I am not for sure were to look next. I guess I just might recap everything.

                      Comment

                        #31
                        Re: Princeton VL1812 Monitor

                        Entire recap done minus a used cap in parallel for the main ac line. And still no constant voltage.

                        Comment

                          #32
                          Re: Princeton VL1812 Monitor

                          How are you doing this testing? Are you loading the output of the supply? Something like a 10 ohm 5 watt resistor on the 5 volt output would be about right. If so, I can see two possible causes. The KA1m0565r has overload sensing. A leaky diode or bad transformer could be overloading it. Or the KA1m0565r itself could be bad.

                          PlainBill
                          For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                          Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                          Comment

                            #33
                            Re: Princeton VL1812 Monitor

                            Most testing has been done without a load. But I then just plug the power supply into the logic board for a load. I will have to look into your possible solutions.

                            Comment

                              #34
                              Re: Princeton VL1812 Monitor

                              Diodes seem ok. I took the three out and they tested fine. The only ones I didn't remove were the four rectifying diodes. So now I will look at the IC or transformer.

                              Comment

                                #35
                                Re: Princeton VL1812 Monitor

                                This leaves 2 parts to replace is TL431C (small 3 legged besides the 4 pin white IC which is optisolator. And second part is SMPS IC (5 or 7 pin on the heatsink to try).

                                Cheers, Wizard

                                Comment

                                  #36
                                  Re: Princeton VL1812 Monitor

                                  I think the 431 is ok. I am looking into the 4 pin smps

                                  Comment

                                    #37
                                    Re: Princeton VL1812 Monitor

                                    Not that one

                                    The 5 or 7 pin black IC mounted on the heatsink.

                                    Cheers, Wizard

                                    Comment

                                      #38
                                      Re: Princeton VL1812 Monitor

                                      Originally posted by Wizard
                                      Not that one

                                      The 5 or 7 pin black IC mounted on the heatsink.

                                      Cheers, Wizard
                                      It's a KA1m0565r - a 4 pin IC.

                                      PlainBill
                                      For a number of reasons, both health and personal, I will no longer be active on this board. Any PMs asking for assistance will be ignored.

                                      Never be afraid to try something new. Remember, amateurs built the ark. Professionals built the Titanic.

                                      Comment

                                        #39
                                        Re: Princeton VL1812 Monitor

                                        Originally posted by Wizard
                                        Not that one

                                        The 5 or 7 pin black IC mounted on the heatsink.

                                        Cheers, Wizard
                                        As bill said there it is a 4 pin device.

                                        Comment

                                          #40
                                          Re: Princeton VL1812 Monitor

                                          Replaced KA1M0565R and power supply is great now. Now just to fix the color being way off.

                                          Comment

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