Is this 55" Hitachi a good buy? (lines on screen)

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  • mattpd
    Badcaps Veteran
    • Oct 2012
    • 301
    • USA

    #1

    Is this 55" Hitachi a good buy? (lines on screen)

    Model 55HDT79

    Screen has horizontal lines

    Price is $80 USD

    Sorry this is this only picture, and I can only see one distinct line around the bottom 1/4. I think I see see faint lines throughout but It could just be the camera...

    If its a bad board, I think I will snatch it up. I don't think I want to hurt my back for a bad panel.
    Attached Files
    Last edited by mattpd; 11-06-2012, 08:00 PM.
  • tom66
    EVs Rule
    • Apr 2011
    • 32560
    • UK

    #2
    Re: Is this 55" Hitachi a good buy? (lines on screen)

    Can't see the fault, but:

    Lines from top to bottom = Don't buy
    Lines from left to right = Buffer failure, will need buffer replaced (~$50) plus a big cap
    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

    • Th3_uN1Qu3
      Believe in
      • Jul 2010
      • 6031
      • Romania

      #3
      Re: Is this 55" Hitachi a good buy? (lines on screen)

      Look at the bottom 1/3 of the picture, there's a (fairly unobtrusive) line from left to right there. I would agree it's not a bad panel.
      Originally posted by PeteS in CA
      Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
      A working TV? How boring!

      Comment

      • tom66
        EVs Rule
        • Apr 2011
        • 32560
        • UK

        #4
        Re: Is this 55" Hitachi a good buy? (lines on screen)

        Originally posted by Th3_uN1Qu3
        Look at the bottom 1/3 of the picture, there's a (fairly unobtrusive) line from left to right there. I would agree it's not a bad panel.
        Ah, I see it now. The only way that could appear like that is a bad buffer. Shouldn't be too difficult to fix. Usually it'll short out the whole lot though, it's quite rare to see single lines fail on a buffer. However, I believe when the buffers fail they take out a cap on the PSU. Or, the cap failing on the PSU takes out the buffers. Not sure which way around it is... haven't done a real Hitachi plasma yet (only an LG based one.)
        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

        • mattpd
          Badcaps Veteran
          • Oct 2012
          • 301
          • USA

          #5
          Re: Is this 55" Hitachi a good buy? (lines on screen)

          Cool. If i can fit it in my car i will go get it today.

          Comment

          • mattpd
            Badcaps Veteran
            • Oct 2012
            • 301
            • USA

            #6
            Re: Is this 55" Hitachi a good buy? (lines on screen)

            I will have the TV later today. Is there any reliable way to tell which of the two buffer boards is bad?

            Comment

            • tom66
              EVs Rule
              • Apr 2011
              • 32560
              • UK

              #7
              Re: Is this 55" Hitachi a good buy? (lines on screen)

              Whichever half of the screen is bad, it is that board. So if lower half is bad, it's the lower buffer.
              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

              • mattpd
                Badcaps Veteran
                • Oct 2012
                • 301
                • USA

                #8
                Re: Is this 55" Hitachi a good buy? (lines on screen)

                Originally posted by tom66
                Whichever half of the screen is bad, it is that board. So if lower half is bad, it's the lower buffer.
                It has boards X-SUS PWB, X-BUS PWB, Y-SUS PWB, SDR-U PWB, SDR-D PWB.

                Which is the lower buffer?

                Comment

                • tom66
                  EVs Rule
                  • Apr 2011
                  • 32560
                  • UK

                  #9
                  Re: Is this 55" Hitachi a good buy? (lines on screen)

                  SDR-U is Upper (Up)
                  SDR-D is Lower (Down)
                  Last edited by tom66; 11-07-2012, 02:27 PM.
                  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

                  • mattpd
                    Badcaps Veteran
                    • Oct 2012
                    • 301
                    • USA

                    #10
                    Re: Is this 55" Hitachi a good buy? (lines on screen)

                    Originally posted by tom66
                    SDR-U is Upper (Up)
                    SDR-D is Lower (Down)
                    Buffer board is AKA scan driver?

                    Comment

                    • tom66
                      EVs Rule
                      • Apr 2011
                      • 32560
                      • UK

                      #11
                      Re: Is this 55" Hitachi a good buy? (lines on screen)

                      Same thing.

                      Responsible for addressing the individual lines on the panel.

                      It feeds an addressing pulse into each line.

                      What tends to happen is the addressing gets stuck for the bad line(s)... so they constantly receive the same address pulse multiple times, and so their pixels are the sum of all of the other pixels in that half of the screen.
                      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

                      • mattpd
                        Badcaps Veteran
                        • Oct 2012
                        • 301
                        • USA

                        #12
                        Re: Is this 55" Hitachi a good buy? (lines on screen)

                        Ok, thank you. I have the tv now, I will post some better pictures soon.

                        I am looking in the service manual and the 42" version does not have these two boards. How is it operating? I assume another board has them built in.

                        Comment

                        • tom66
                          EVs Rule
                          • Apr 2011
                          • 32560
                          • UK

                          #13
                          Re: Is this 55" Hitachi a good buy? (lines on screen)

                          Possibly a single board (Y-sustain and buffer components), two board (Y-sustain and single buffer with both upper and lower stuff on it) or an omission in the manual.
                          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

                          • mattpd
                            Badcaps Veteran
                            • Oct 2012
                            • 301
                            • USA

                            #14
                            Re: Is this 55" Hitachi a good buy? (lines on screen)

                            Ok, I got the tv up and running. I will try to describe the problem better. That one 1cm line you can see is the only part of the picture that is displaying correctly. The entire remainder of the screen has one horizontal line of working pixels followed by one line of black pixels and this pattern repeats all the way through. So every other row seems to be working. Still a buffer board problem?
                            Attached Files

                            Comment

                            • tom66
                              EVs Rule
                              • Apr 2011
                              • 32560
                              • UK

                              #15
                              Re: Is this 55" Hitachi a good buy? (lines on screen)

                              I have seen that both with loose buffer connections and with bad buffers. The displays on some older plasmas are interlaced. I suspect you only need to replace the one with the line on it.
                              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

                              • mattpd
                                Badcaps Veteran
                                • Oct 2012
                                • 301
                                • USA

                                #16
                                Re: Is this 55" Hitachi a good buy? (lines on screen)

                                So instead of having a buffer for top and one for the bottom, there is one for the even rows and one for the odds?

                                Comment

                                • tom66
                                  EVs Rule
                                  • Apr 2011
                                  • 32560
                                  • UK

                                  #17
                                  Re: Is this 55" Hitachi a good buy? (lines on screen)

                                  No, the buffers control each part of the screen themselves, but when one goes bad, it can cause a problem with the -whole- of that scan. So the odd lines are energised, but the TV sustain senses that short, the TV goes blank for that field, then the evens are fine so you see all of those light up, etc. That's my theory. I've never seen a buffer line failure, only a completely dead buffer.
                                  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

                                  • mattpd
                                    Badcaps Veteran
                                    • Oct 2012
                                    • 301
                                    • USA

                                    #18
                                    Re: Is this 55" Hitachi a good buy? (lines on screen)

                                    I think you nailed it! This is the bottom buffer board. Is there anything else I need to check before powering on with a new board?
                                    Attached Files

                                    Comment

                                    • tom66
                                      EVs Rule
                                      • Apr 2011
                                      • 32560
                                      • UK

                                      #19
                                      Re: Is this 55" Hitachi a good buy? (lines on screen)

                                      Reseat every connector going to the plasma panel, I have seen one bad connector on a Panasonic cause -all- the screen to go interlaced.

                                      Be super, duper careful with them as breaking them will make the panel useless.
                                      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

                                      • mattpd
                                        Badcaps Veteran
                                        • Oct 2012
                                        • 301
                                        • USA

                                        #20
                                        Re: Is this 55" Hitachi a good buy? (lines on screen)

                                        Is there anything that may have caused this IC to explode other than just old age? These boards are kind of expensive. I don't want to hear a pop when I plug it in. Should I check anything on y-sus?

                                        By the way the square in the middle of the right IC is hole where is failed. It's hard to tell from the picture.
                                        Last edited by mattpd; 11-07-2012, 09:09 PM.

                                        Comment

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