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Samsung LN32B460 turns on only after repeated attempts

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    #21
    Re: Samsung LN32B460 turns on only after repeated attempts

    Originally posted by budm View Post
    You are right, I made the typo, it should be CM804. But since the backlights do come on and the boost voltage is OK, then something on the main board is telling it to turn off the PS_ON signal so the votgae goes back down to 162V if I read post 15 correctly, but I do need to find out if at the same time the PS_ON also goes down. I think the problem is in the main board. Does it stay on if the T-CON board is disconnected?
    I didn't catch the typo, but just assumed the CM804. By PS_on do you mean pin 1 on CNM802? That goes up to 1.8V on power attempts, then back down close to 0. There is another ribbon cable connected to the main board beside the one coming from the PS It disappears behind the metal shielding, but I assume it leads to the T-CON board. Disconnecting that cable has no effect on powering up.

    Comment

      #22
      Re: Samsung LN32B460 turns on only after repeated attempts

      Originally posted by tom66 View Post
      I would suspect main board problems then. Everything on the PSU seems to be fine. One final check - INV ON/OFF does this go HIGH (>2V) on every power up or just the ones that succeed.
      INV ON/OFF goes to <0.5V on power on attempts, 4.7V on the one rare attempt that succeeded.

      Comment

        #23
        Re: Samsung LN32B460 turns on only after repeated attempts

        Check the voltage regulators on the main board (circled in red). My sig file has instructions.
        Attached Files
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        If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

        We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

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        Comment

          #24
          Re: Samsung LN32B460 turns on only after repeated attempts

          Originally posted by retiredcaps View Post
          Check the voltage regulators on the main board (circled in red). My sig file has instructions.
          I tested them but I am having a hard time finding the data sheets. What I have so far...

          IC105
          78M098
          KV 9A
          8.84
          0.00
          13.07

          IC427
          119nB
          17-18
          0.00
          1.811
          3.26

          Comment

            #25
            Re: Samsung LN32B460 turns on only after repeated attempts

            Originally posted by Dardo View Post
            78M098
            KV 9A
            8.84
            0.00
            13.07
            http://pdf1.alldatasheet.com/datashe.../L78M09AB.html

            78M09 is a 7800 series with 9V as the output voltage. At 8.84 it is 1.78% out. I use +/- 1% tolerance and others use +/- 2%. For now, assume it is good, but if you grasping at straws ...

            IC427
            119nB
            17-18
            0.00
            1.811
            3.26
            17-18 is a 1117-18 fixed regulator. 1.8V should be the output voltage. IC427 is good.
            --- begin sig file ---

            If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

            We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

            Please do not post inline and offsite as they slow down the loading of pages.

            --- end sig file ---

            Comment

              #26
              Re: Samsung LN32B460 turns on only after repeated attempts

              Thanks, I was hoping I read those numbers right. Any other ideas?

              Comment

                #27
                Re: Samsung LN32B460 turns on only after repeated attempts

                If you turn the main board over there are a lot more voltage regulators on the back to test.
                Please upload pictures using attachment function when ask for help on the repair
                http://www.badcaps.net/forum/showthread.php?t=39740

                Comment

                  #28
                  Re: Samsung LN32B460 turns on only after repeated attempts

                  Originally posted by tom66 View Post
                  I would suspect main board problems then. Everything on the PSU seems to be fine. One final check - INV ON/OFF does this go HIGH (>2V) on every power up or just the ones that succeed.
                  Since this does not go over 2V on power up, does that indicate a main board problem?

                  Comment

                    #29
                    Re: Samsung LN32B460 turns on only after repeated attempts

                    Does it go high when it succeeds?
                    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                    Comment

                      #30
                      Re: Samsung LN32B460 turns on only after repeated attempts

                      Originally posted by tom66 View Post
                      Does it go high when it succeeds?
                      Yes it goes to 4.7V when it succeeds, < 0.5V during unsuccessful attempts

                      Comment

                        #31
                        Re: Samsung LN32B460 turns on only after repeated attempts

                        OK, so that pretty much puts the problem on the main board. Is there a part # for your main board - may be able to get schematics.
                        Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                        For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                        Comment

                          #32
                          Re: Samsung LN32B460 turns on only after repeated attempts

                          Originally posted by selldoor View Post
                          If you turn the main board over there are a lot more voltage regulators on the back to test.
                          Yup, I didn't even notice that. Good thing selldoor is our resident eagle eyes. 5 more to check.
                          Attached Files
                          --- begin sig file ---

                          If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                          We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                          Please do not post inline and offsite as they slow down the loading of pages.

                          --- end sig file ---

                          Comment

                            #33
                            Re: Samsung LN32B460 turns on only after repeated attempts

                            Originally posted by tom66 View Post
                            OK, so that pretty much puts the problem on the main board. Is there a part # for your main board - may be able to get schematics.
                            Thanks Tom
                            There are 2 stickers with part #'s
                            BN97-03466B
                            BN96-11524A 657A

                            Comment

                              #34
                              Re: Samsung LN32B460 turns on only after repeated attempts

                              Originally posted by retiredcaps View Post
                              Yup, I didn't even notice that. Good thing selldoor is our resident eagle eyes. 5 more to check.
                              Thanks selldor and retiredcaps.
                              OK I checked the voltage regulators. I assume I need the readings when the screen is on, as some have power only when in standby.

                              IC601
                              1117
                              0944EG
                              pin 1 = 0.017
                              pin 2 = 1.264
                              pin 3 = 3.28

                              IC505
                              1117
                              0944EG
                              pin 1 = 0.631
                              pin 2 = 1.891
                              pin 3 = 4.75

                              IC109
                              17-33
                              0944DG
                              pin 1 = 0.017
                              pin 2 = 3.29
                              pin 3 = 5.10

                              IC106
                              17-33
                              0944DG
                              pin 1 = 0.017
                              pin 2 = 3.31
                              pin 3 = 4.75

                              IC110
                              7805AF
                              943
                              pin 1 = 8.82
                              pin 2 = 0.016
                              pin 3 = 5.05

                              I'm guessing there may be a problem with IC505?

                              Comment

                                #35
                                Re: Samsung LN32B460 turns on only after repeated attempts

                                IC505 is fine - adjust measures 0.631V so output should be 0.631V + 1.25V(ref) = 1.881V. Actually 1.891V but that's fine.

                                As you are trying to track down an intermittent fault, try to get measurements with the TV "failed". So, when it fails to start up, measure the voltages while it is in this mode, before it goes back to standby.
                                Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                                For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                                Comment

                                  #36
                                  Re: Samsung LN32B460 turns on only after repeated attempts

                                  Originally posted by Dardo View Post
                                  IC505
                                  1117
                                  0944EG
                                  pin 1 = 0.631
                                  pin 2 = 1.891
                                  pin 3 = 4.75

                                  I'm guessing there may be a problem with IC505?
                                  The readings say it is good. Re-read my link on how to test a voltage regulator.

                                  1.891 - 0.631= 1.26.

                                  Having said that, there is a possibility that the voltage on pin 1 is incorrect. The components feeding pin 1 could be off or pin 1 itself on the regulator can be bad.

                                  Without a service manual, there is no way to be 100% sure.

                                  The "common" output voltages are normally 1.25, 1.5, 1.8, 2.5 and 3.3.

                                  1.891 is 5.05% out of tolerance when compared to 1.8. So if IC505 is really supposed to be outputting 1.8, then the regulator is bad.

                                  edit: tom66 beat me -> I'm too slow today.
                                  --- begin sig file ---

                                  If you are new to this forum, we can help a lot more if you please post clear focused pictures (max resolution 2000x2000 and 2MB) of your boards using the manage attachments button so they are hosted here. Information and picture clarity compositions should look like this post.

                                  We respectfully ask that you make some time and effort to read some of the guides available for basic troubleshooting. After you have read through them, then ask clarification questions or report your findings.

                                  Please do not post inline and offsite as they slow down the loading of pages.

                                  --- end sig file ---

                                  Comment

                                    #37
                                    Re: Samsung LN32B460 turns on only after repeated attempts

                                    The regulator should be OK, I have seen some Samsung LCDs which use 1.9V rails instead of 1.8V. Don't ask me why, though! The Vref is 1.26V, which is 0.8% out.
                                    Please do not PM me with questions! Questions via PM will not be answered. Post on the forums instead!
                                    For service manual, schematic, boardview (board view), datasheet, cad - use our search.

                                    Comment

                                      #38
                                      Re: Samsung LN32B460 turns on only after repeated attempts

                                      Originally posted by tom66 View Post
                                      IC505 is fine - adjust measures 0.631V so output should be 0.631V + 1.25V(ref) = 1.881V. Actually 1.891V but that's fine.

                                      As you are trying to track down an intermittent fault, try to get measurements with the TV "failed". So, when it fails to start up, measure the voltages while it is in this mode, before it goes back to standby.
                                      The voltages are the same on failed startups.

                                      Comment

                                        #39
                                        Re: Samsung LN32B460 turns on only after repeated attempts

                                        Thanks for everyone's help. I'm thinking it is time to find a replacement main board, which is board # BN97-03466B, and the part # is BN96-11524A.
                                        I'm finding 3 different part #'s for that board #
                                        BN96-11524A
                                        BN96-11524B
                                        BN96-11524C

                                        Does anyone know if I can use the B or C version, or if I need to stick with the A version?

                                        Comment

                                          #40
                                          Re: Samsung LN32B460 turns on only after repeated attempts

                                          Can anyone tell me what the part circled red in the pic is? Does anyone have a schematic?
                                          Thanks
                                          Attached Files

                                          Comment

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