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Philips Magnavox 32MF338B/27

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    #1

    Philips Magnavox 32MF338B/27

    There is another thread about the same problem here: https://www.badcaps.net/forum/showth...=32mf338b%2F27

    The conclusion was that the power supply/inverter board needed to be replaced. There wasn't much participation in that thread and as such I'm hoping to glean more about this problem here.

    The unit tries to turn on. Power blinks green several times, then it goes to red standby.

    Detailed pics of the board are attached.

    There are burn marks on the board which correspond to the 22N055s on the solder side of the board.

    I just found this site: http://www.electronicrepairguide.com/lcd-tv-repair.html which, while isn't the same TV, is quite a similar power supply.

    Checking the three large diodes with my Ohm Meter, I show open only one way (if memory serves, that's good, right? )

    Checking the rectifier diodes, I also show open one way. Diodes appear to be good. Not sure what points to use to test the inverter coils or if I need to remove them for testing.

    Thanks in advance for any guidance!
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    #2
    Re: Philips Magnavox 32MF338B/27

    Bump for great justice.

    Comment

      #3
      Re: Philips Magnavox 32MF338B/27

      I've fixed 3 of these Funai design TVs now. 2 had Emerson branding on them and 1 Magnavox. All had one or more burned spots on the board like that and the same symptoms as yours. I believe I paid around $30 for the power supplies so to me it wasn't even worth messing with a repair on the board itself.

      Comment

        #4
        Re: Philips Magnavox 32MF338B/27

        From a time vs money standpoint, no, I suppose it isn't. I'm hoping to learn something from this as well, though. Hopefully someone can guide me.

        Believe me, simply buying a board has crossed my mind a few times.

        Comment

          #5
          Re: Philips Magnavox 32MF338B/27

          Bumparoonie!

          Comment

            #6
            Re: Philips Magnavox 32MF338B/27

            What I learned from the ones I worked on is that the parts are absolute pieces of crap. There are no heat sinks on the power supplies so I don't know how they expect them to last any amount of time. Its a wonder it doesn't catch fire.

            Comment

              #7
              Re: Philips Magnavox 32MF338B/27

              The power supply is self oscillating design with no controller logic at all. This is what happens when you say to the engineer, "but can you make it cheaper?"

              Essentially it will drive current straight into a short circuit, with little concern; typically, the fuse will blow, but if that does not happen, it will nuke the transformer, MOSFET, and various other parts in the ac line and output path. If there is a failure of the feedback circuit, or a single small capacitor fails on the primary, the output can climb to more than 3x its normal rating, resulting in severe damage to the rest of the set and the LCD panel. Should neither of those happen, the components on the PCB run so hot, cold joints and thermal expansion are almost guaranteed. They are built to the lowest possible price, and designed to have a short lifespan.

              These are absolute piles of junk, worse than even the Vestel sets I hate.
              Last edited by tom66; 08-15-2013, 08:58 AM.
              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

                #8
                Re: Philips Magnavox 32MF338B/27

                Originally posted by tom66 View Post
                The power supply is self oscillating design with no controller logic at all. This is what happens when you say to the engineer, "but can you make it cheaper?"

                Essentially it will drive current straight into a short circuit, with little concern; typically, the fuse will blow, but if that does not happen, it will nuke the transformer, MOSFET, and various other parts in the ac line and output path. If there is a failure of the feedback circuit, or a single small capacitor fails on the primary, the output can climb to more than 3x its normal rating, resulting in severe damage to the rest of the set and the LCD panel. Should neither of those happen, the components on the PCB run so hot, cold joints and thermal expansion are almost guaranteed. They are built to the lowest possible price, and designed to have a short lifespan.

                These are absolute piles of junk, worse than even the Vestel sets I hate.
                Agreed 100%. All of these that I fixed I never even tested the voltage on the board. I opened it up, saw burn spots everywhere and ordered a replacement.

                Comment

                  #9
                  Re: Philips Magnavox 32MF338B/27

                  I do believe I may have found one even worse than these Tom. It's a 32" Coby set. Some type of control board issue I believe that I haven't tackled yet. The panel is made completely of plastic and the boards look horrible. Its sandwiched between the front and back covers and held by nothing else. You have to lean the panel forward out of the back cover to access the boards that are screwed to the cover itself instead of being attached to the panel.

                  Comment

                    #10
                    Re: Philips Magnavox 32MF338B/27

                    Thanks, all. The same answer from 3 or 4 people on this site is good enough for me. I'll just rape the board for anything useful and recycle the TV.

                    Thanks again!

                    Comment

                      #11
                      Re: Philips Magnavox 32MF338B/27

                      Or, you could just replace the board. . .
                      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

                        #12
                        Re: Philips Magnavox 32MF338B/27

                        I considered that as well. But how long before it happens again?

                        Comment

                          #13
                          Re: Philips Magnavox 32MF338B/27

                          I had to wait a few weeks and looked daily to find one for around $30. I see two of yours on ebay but they are $55. I certainly wouldn't keep the set for myself because I'm sure it will happen again one day but at $30 how can you go wrong? I sold the last one I picked up for $125.

                          Comment

                            #14
                            Re: Philips Magnavox 32MF338B/27

                            If I knew it were going to last a few years, I wouldn't feel so bad. I don't wanna repair it, sell it, then have someone else end up with junk. And going even further, most people will just throw it out instead of properly recycling it. I'd hate for it to end up in a landfill. Maybe I'll fix it and stick it in my bedroom to use it until it dies again.

                            Comment

                              #15
                              Re: Philips Magnavox 32MF338B/27

                              Well, either way I can't see destroying one over a PS. I always hunt for a good deal on parts. Don't mind putting the TV in the corner for a bit to wait for a better price.

                              Comment

                                #16
                                Re: Philips Magnavox 32MF338B/27

                                Fair enough. I have a big enough basement. I'm convinced!

                                Comment

                                  #17
                                  Re: Philips Magnavox 32MF338B/27

                                  http://www.ebay.com/itm/Emerson-LC32...item3a837232db

                                  Not too bad on this one

                                  Comment

                                    #18
                                    Re: Philips Magnavox 32MF338B/27

                                    Even better.

                                    http://www.ebay.com/itm/SYLVANIA-LC3...item2ec9bf1b7b

                                    Comment

                                      #19
                                      Re: Philips Magnavox 32MF338B/27

                                      Originally posted by aaronwt6 View Post
                                      Even better.

                                      http://www.ebay.com/itm/SYLVANIA-LC3...item2ec9bf1b7b
                                      I saw both of these. I'm concerned about the second one. The cable wraps over where the 4 large diodes are. It's difficult to tell if it's burned as mine is, or not.

                                      Comment

                                        #20
                                        Re: Philips Magnavox 32MF338B/27

                                        Looks like it may be a bit dark. Fact is any with a bit of use will be. That area is running hot.

                                        Comment

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