Magnavox 50mf231d/37 just buzzing

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  • macsr00l
    New Member
    • Mar 2011
    • 5
    #1

    Magnavox 50mf231d/37 just buzzing

    Hello everyone!

    I'm a new member as of today, my name is Wes and I'm located in the Grand Rapids area of Michigan. Although we don't have any snow to speak of right now, it is still beyond cold here!

    I found this site to be a valuable resource when making the initial repair to the TV I'll talk about below, but now I need more help and was hoping I could get some assistance here. After all, I'm pretty much an amateur when it comes to these type of repairs.

    I've obtained this 50" plasma model (Magnavox 50mf231d/37) from a relative who was going to throw it away, and I'm really hoping to be able to make it work for me! The TV will, when powered up, click twice and then start a (rather loud) buzzing noise. No picture whatsoever. I've tried in vain to locate the exact source of the buzzing inside the case, but I will mention that when buttons on the TV/Remote are pressed (as in, when the picture on the TV *would* be changing) the buzzing changes pitch. Probably not important, but I figured it was worth mentioning.

    My initial search showed that this particular model's weak spot lies in two caps on the power supply board which tend to go bad within a year or two. Sure enough, one was bulged and so I replaced both of them just in case the other was bad too. Unfortunately, that didn't fix the TV...

    I have the service manual for this model, and I've already tried to get the error code by shorting the SDM pins - one long blink which repeats, which if I'm reading right means "I^2C1 blocked" (the "I^2" being "I" squared). Of course, I have absolutely no idea what this means.

    I do not have a multimeter, but I will be picking one up later today and I'm willing to do all the testing that is required of me. I've never used one before, so I may need a little bit of coaching. I can post any pics that are needed as well, and I believe I know how to follow the rules and use the manage attachments feature so as to not piss anyone off (I'm all about being courteous and following forum rules).

    If anyone has any suggestions or would be willing to walk me through this, I'd be extremely grateful! Thanks in advance for any help that is offered.
    Tags: None
    • Scenic
      o.O
      • Sep 2007
      • 2640
      • Germany
      #2
      Re: Magnavox 50mf231d/37 just buzzing

      the I²C bus is some sort of communication platform between the ICs..
      think of it like ethernet between computers.

      http://en.wikipedia.org/wiki/I²C

      so this kinda sounds like something is blocking the communication between the ICs..

        Comment

        • PlainBill
          Badcaps Legend
          • Feb 2009
          • 7034
          • USA
          #3
          Re: Magnavox 50mf231d/37 just buzzing

          Does the TV stay on? If I recall correctly, a bad I²C bus on Philips / Maganvox sets results in the system shutting down.

          A common problem with plasma sets is a failure of the buffers or a sustain board. If the TV stays on, a starting point is to measure the output voltages of the power supply, especially those going to the sustain boards.

          What is the chassis number of this set? My usual sources don't show a service manual for 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

            • macsr00l
              New Member
              • Mar 2011
              • 5
              #4
              Re: Magnavox 50mf231d/37 just buzzing

              I believe the chassis is EP1.1U - could that be correct? I found that somewhere online and that is the service manual that I have.

              The TV does stay on - I've kept it on for up to 30 mins or so in this state, to see if anything would change once parts warmed up, etc. It has yet to turn back off on me.

              Any advice on which are the best points to test voltage?

              Oh, another random fact that could be important - I've disconnected the cables running to the Y board and the X board and then powered up the TV, and the buzzing only happens if one or both of these are connected.

                Comment

                • rayrod81
                  Badcaps Veteran
                  • Oct 2010
                  • 205
                  #5
                  Re: Magnavox 50mf231d/37 just buzzing

                  Sounds like a broken plasma panel. Usually if the screen is broken then the tv will turn on but buzz fairly loud and show no picture. It might be a crack near the edge of the panel that cannot be seen unless you disassemble the panel.

                    Comment

                    • macsr00l
                      New Member
                      • Mar 2011
                      • 5
                      #6
                      Re: Magnavox 50mf231d/37 just buzzing

                      I think I've managed to successfully measure the various voltages going to the various boards, and all of them seem right on. There are 5v sources going to both sustain boards and the buffer, and a 3v, 5v, and 12v going to the SSB. All are within .2 volts of what they're supposed to be. I don't *think* I'm missing anything, but if I am please let me know!

                      The service manual lists a few tips on how to diagnose voltage problems in the SSB, which I haven't braved yet (still has the metal cage on it). Does it sound like my problem could possibly be in here, or should I just stay away from this area?

                        Comment

                        • macsr00l
                          New Member
                          • Mar 2011
                          • 5
                          #7
                          Re: Magnavox 50mf231d/37 just buzzing

                          I sure hope it isn't a broken panel! It doesn't seem like that would be the case, since this belonged to an elderly family member who would never be able to move it and probably wouldn't even touch it other than to dust. But you never know. If I'm still stumped in a few days I'll probably brave taking the whole thing apart and checking the panel, but I'm going to save that until I'm truly desperate. Right now I'm just terrified that I'm going to mess this up more than it already is! :S

                            Comment

                            • macsr00l
                              New Member
                              • Mar 2011
                              • 5
                              #8
                              Re: Magnavox 50mf231d/37 just buzzing

                              ...Ok, I think I found the problem...

                              Up near the top left corner of the panel (looking from the rear) there is a small, metal, open-ended tube, which had a piece of broken glass inside it. The glass piece had a circular bottom and a top which looks like a mini christmas tree light bulb. It looks like the metal tube put stress on the glass piece (which appears to have at one time been attached directly to the plasma panel) and broke it off. The broken part was just sitting in the tube, I had to pull it out.

                              Anyone know what this is and what its purpose is? I have no idea, but if it was attached directly to the panel I'm losing hope that it's something I can fix...
                              Attached Files

                                Comment

                                • PlainBill
                                  Badcaps Legend
                                  • Feb 2009
                                  • 7034
                                  • USA
                                  #9
                                  Re: Magnavox 50mf231d/37 just buzzing

                                  Originally posted by macsr00l
                                  ...Ok, I think I found the problem...

                                  Up near the top left corner of the panel (looking from the rear) there is a small, metal, open-ended tube, which had a piece of broken glass inside it. The glass piece had a circular bottom and a top which looks like a mini christmas tree light bulb. It looks like the metal tube put stress on the glass piece (which appears to have at one time been attached directly to the plasma panel) and broke it off. The broken part was just sitting in the tube, I had to pull it out.

                                  Anyone know what this is and what its purpose is? I have no idea, but if it was attached directly to the panel I'm losing hope that it's something I can fix...
                                  That is the evacuation tube for the panel. The TV is junk unless you can find a good panel (or another TV using the same panel).

                                  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

                                    • mbates14
                                      Senior Member
                                      • May 2005
                                      • 169
                                      #10
                                      Re: Magnavox 50mf231d/37 just buzzing

                                      or glass blow another evacuation stem on it, and pump down the panel, and pump it back full of gas. (good luck on that). Assuming there are NO other cracks ANYWHERE else.

                                        Comment

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