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    #21
    Re: LCD Monitor inverter gets way too hot

    Originally posted by Toasty
    @Wizard - Thank you. I thought as much, but I haven't seen enough of these circuits to be sure.
    @PlainBill - Wow! Nice. TY. ...another walking database.
    Google is your friend. I recognized the package as one commonly used for caps and the logo from another thread - the cap that flamed out. Now I know the manufacturer.

    Originally posted by Toasty
    Poly = polystyrene, correct?

    It is connected to both driver transistors collectors. If it is failing, it could be the problem. But, I'd expect no or dim lights then, as it would be shorting their output to the transformer.

    Are there different wattages of these tubes at the same length? Could this be a case of 20w tubes in a 12w inverter?

    FYI- Inverter p/n is: 715T1537-4
    I'm no expert on CCFL tubes, but in florescent lighting if two tubes are the same length, but different diameter, the smaller diameter one draws less current. It thus seems logical that if someone substituted a larger diameter tube the exciting voltage to be the same, but once excited the current requirements would be higher. This is a SWAG!! Don't bet on it.

    That part is available here for $17.99. I'm prejudiced - I've spent far too much time farting around trying to figure out what is failing on stuff like this. To me $17.99 is a bargain, given you don't know what has been changed. The downside is if the tubes pull too much power, you're out the $$$.

    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: LCD Monitor inverter gets way too hot

      Well, if your into experimenting, for $10 try this:

      http://www.auctiva.com/stores/viewst...arch=80LL15T-7

      Either way, if you get a chance to pull the transformer, pics of the bottom would be appreciated.

      **
      As stated by PlainBill, for those that don't know-

      SWAG = Scientific Wild Ass Guess

      @PlainBill - I tried that link earlier, when I was searching, and it appears dead.
      Last edited by Toasty; 03-09-2009, 08:41 PM.
      veritas odium parit

      Comment


        #23
        Re: LCD Monitor inverter gets way too hot

        It looks obvious to me that these lamps have very little time being lit,just by the way they look on the ends ,even after a short time you can usually see dark areas around the cathode where it gets hot.Resistor R7 is missing ,who knows if it is supposed to be .
        Attached Files
        Last edited by CudaDave70; 03-09-2009, 08:44 PM.
        I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

        Comment


          #24
          Re: LCD Monitor inverter gets way too hot

          More good tips for me ,I also really like the link to the Auctiva store ,thanks,I will spend more than ten bucks there. There are other other items I use.
          The inverter for 17.99 I had located that store but someone beat me to it ,that is a fair price for that POS.
          Everyone else that sells these wants twice as much,I am not going to pay that. I will buy a new universal one for half that first and make it fit.
          I would not bother but these little Monitor -TV's are nice and have great video on them. I am going to pull the transformer and replace it I will post a pic of it when I take it off .
          I will always spend more money trying to save a little,but I mostly do this for the simple reason of something to work on and try to figure out why it won't work then something to smash after I fail (just kidding) I have grown out of that (finally).
          Thanks A bunch you guy are great. I am going shopping right now
          Dave
          I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

          Comment


            #25
            Re: LCD Monitor inverter gets way too hot

            The money I save on haircuts I use on stupid decisions to try and fix junk.Here are some pics for anyone interested ,of the transformer underside
            Attached Files
            I am pretty good at keeping a secret,it's the people I tell that can't keep their mouth shut!

            Comment


              #26
              Re: LCD Monitor inverter gets way too hot

              Thanks for the pics. NOW it makes sense why it APPEARED to have the secondary shorted.

              In the first 2 photos of the bottom-
              The secondary output high pin is the only one wired on the upper end (right). The upper left pin is unused electrically. The secondary ground is the lower left pin.

              Thanks!
              veritas odium parit

              Comment


                #27
                Re: LCD Monitor inverter gets way too hot

                >>...really like the link to the Auctiva store ,thanks,I will spend more than ten bucks there. There are other other items I use.<<

                Yes. I just went back and looked through a brief listing on that store. I see he has many items that people here are looking for that I see mentioned on a daily basis. Such as the C5707's and those little solder-in fuses for the inverters. Shipping $$ seems fair and it's only $0.10 shipping for each additional item.
                veritas odium parit

                Comment


                  #28
                  Re: LCD Monitor inverter gets way too hot

                  I ordered some of the parts I used for the HP 1940 the HP 1940 repair I did last weekend from this store. Shipping was fast, even to Norway, and the parts was as advertised.
                  ------------
                  Be a mensch

                  Comment


                    #29
                    Re: LCD Monitor inverter gets way too hot

                    I have the same board except mine ends in -2 instead of -4 assume it is a version #. I have a obvious part bad on mine in location C11. It is a blue part, what is this part? My board is also blackened to the right of the transformer. This was a tv given to my son and it is an experiment to see if we can get it to work. If any one has the part # that I need to replace this I would appreciate the help. Thank you for your time

                    Comment


                      #30
                      Re: LCD Monitor inverter gets way too hot

                      Originally posted by allnighters
                      I have the same board except mine ends in -2 instead of -4 assume it is a version #. I have a obvious part bad on mine in location C11. It is a blue part, what is this part? My board is also blackened to the right of the transformer. This was a tv given to my son and it is an experiment to see if we can get it to work. If any one has the part # that I need to replace this I would appreciate the help. Thank you for your time
                      C11 is a capacitor. As far as part number, 1 picture > 1000 words.

                      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


                        #31
                        Re: LCD Monitor inverter gets way too hot

                        Here is a couple photos
                        Attached Files

                        Comment


                          #32
                          Re: LCD Monitor inverter gets way too hot

                          Is this repairable?

                          Comment


                            #33
                            Re: LCD Monitor inverter gets way too hot

                            the caps look like bad brands. replace those. but... the transformer looks overheated. i dont know how to test those but some one here does i bet
                            sigpic

                            (Insert witty quote here)

                            Comment


                              #34
                              Re: LCD Monitor inverter gets way too hot

                              Originally posted by allnighters
                              I have the same board except mine ends in -2 instead of -4 assume it is a version #. I have a obvious part bad on mine in location C11. It is a blue part, what is this part? My board is also blackened to the right of the transformer. This was a tv given to my son and it is an experiment to see if we can get it to work. If any one has the part # that I need to replace this I would appreciate the help. Thank you for your time
                              Originally posted by allnighters
                              Is this repairable?
                              The general rule of thumb is "With enough time and parts we can repair anything."

                              C11 is the same value as C10. The numbers on (or better yet a picture) of C10 will help identify it. You will also want to scrape away any charred areas around C11. Make sure you match the original part, both for value and voltage.

                              The overheated area between L1 and PT1 isn't unusual. Odds are the driver FETs for PT1 are under there. Given that C11 smoked, odds are the inverter was working properly. A picture of the bottom side of the circuit board would be helpful. There might also be a fuse on that side.

                              PlainBill

                              As ratdude suggested, replacing C1 and C7? (The electrolytics) would be a good idea.
                              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


                                #35
                                Re: LCD Monitor inverter gets way too hot

                                Here is a pic of the bottom. You guys are great help. I tried a couple of sites to buy this board but no one has it in stock for a decent price. So it looks as a rebuild may be the way to go. How would i determine the correct specs for this capacitor? There seems to be no numbers or any thing on c-10 to match it up with?
                                Attached Files

                                Comment


                                  #36
                                  Re: LCD Monitor inverter gets way too hot

                                  I can't remember where I have read this but I think that blue cap is part of the lamp feedback (to determine open lamp shutdown?) so if it is burnt, there is a possibility the lamp connected to CON3 may be suspect.

                                  Anyways, good luck.

                                  Comment


                                    #37
                                    Re: LCD Monitor inverter gets way too hot

                                    Originally posted by allnighters
                                    Here is a pic of the bottom. You guys are great help. I tried a couple of sites to buy this board but no one has it in stock for a decent price. So it looks as a rebuild may be the way to go. How would i determine the correct specs for this capacitor? There seems to be no numbers or any thing on c-10 to match it up with?
                                    There are a couple of ways. The easiest is to use a DMM with capacitance feature to check the value of C10 (out of circuit). Another is to search for application notes on the PWM controller.

                                    I'm feeling pumped - the Twins beat the White Sox, sweeping the series so here is a quick rundown on the circuit. I've marked up your picture a little.

                                    The red circle is the input fuse. That is either an O (oh) indicating the fuse rating or a 0 (zero) indicating it is a jumper.

                                    The yellow circle - U1 is the PWM controller. Your picture is excellent, but I can't read the part number. That information MAY help with C11.

                                    The green circle (Q?) is a power FET, which boosts the output of U1 to provide drive current to the gates of - Blue circle - the power FETs (Q7 and Q8) which drive the primary of the transformer (pink circle).

                                    The brown circle is the high voltage end of the transformer secondary. Note that it goes through C10 and C11 to drive the CCFLs. The orange circle is L2, which provides CCFL current feedback to the PWM.

                                    NOW, to determine the value of C10 and C11, I suggest a couple of approaches. First, as I mentioned, measure the value of C10. Google application notes and data sheets for the PWM and see if they have a typical circuit. Google CCFL Inverter schematics and see if anything uses the same design. I know there is an extensive application note on inverter design out there from (Sanyo?), use a capacitor of the same voltage.

                                    And while lucky13 is wrong about it being part of the lamp feedback, it is reasonable to assume a bad CCFL caused excessive current through the capacitor and burned it.

                                    PlainBill
                                    Attached Files
                                    Last edited by PlainBill; 07-29-2009, 09:51 PM.
                                    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


                                      #38
                                      Re: LCD Monitor inverter gets way too hot

                                      Here is a little better photo. Thank you for all of the info you have given me.
                                      Attached Files

                                      Comment


                                        #39
                                        Re: LCD Monitor inverter gets way too hot

                                        Originally posted by allnighters
                                        Here is a little better photo. Thank you for all of the info you have given me.
                                        Well, U1 is a TL5001C, a general purpose PWM controller. Since it's not specifically designed to be used in a backlight inverter application notes won't be much help.

                                        I did find several schematics for inverters, which did provide a little information. All of them used either a 15pf or 27pf 3KV capacitor. Checking the value of the good cap would be a very good idea.

                                        It's been mentioned several times in other threads. The usual way to test inverters / backlights is to use a case mod light kit. These consist of an inverter and two 12" CCFLs and cost about $10. Use the kit inverter to test the existing CCFLs; use the kit CCFLs to test the (repaired) inverter. You will be dealing with voltages of 700 - 1000 volts and currents of about 5 ma so precautions are appropriate.

                                        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


                                          #40
                                          Re: LCD Monitor inverter gets way too hot

                                          This is an old post but I am having the same issue with a magnavox lcd TV. It is the same board and the c10 and c11 cap values are 22pf 3kv.

                                          Was there any resolution to this problem?

                                          Comment

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