Announcement

Collapse
No announcement yet.

Elo 1525L power board ptb-1218

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Elo 1525L power board ptb-1218

    There was an issued with this board when I bought the monitor for repairs.
    I replaced a 10uf 50v on c814 and a 47uf 25v on c807. I the got a picture on the monitor without backlamps on. (possible ccfl's' bad, no backups laying around atm) There was a clicking going on the board while the inverter was plugged in but I dont hear well anymore, so finding the location was difficult. Well, here is what happened. I got out the DMM and started probing around. Probing a Mosfet 4n60b sss s0220 while just checking for power I shorted pin 2,3 D,S I belive they are. Now thre isnt any power getting to the top half of the board. OUCH! Any pointers? What did I blow?
    Attached Files

    #2
    Re: Elo 1525L power board ptb-1218

    Better images?
    Attached Files

    Comment


      #3
      Re: Elo 1525L power board ptb-1218

      That was clever. You shorted across Q803, the power FET. Possible collateral damage could include D803, D804, D806, I801, ZD801, and maybe even Q806.

      The first step would be to check the voltage across the large cap (with power applied). It should be about 1.4 times the AC line voltage.

      If you get that, remove power and allow time for the large cap to discharge. Next, check the resistance across each of the diodes I listed. This can be done in circuit. I would use the 200 ohm range on the DMM. Anything that doesn't read > 200 ohms (especially anything that reads < 10 ohms) should be lifted and tested out of circuit. Do the same for the two transistors. Follow that by testing in both directions with the DMM on the diode test function. You should get conduction in only one direction.

      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


        #4
        Re: Elo 1525L power board ptb-1218

        Originally posted by BlkSmth View Post
        Better images?
        1) If your camera has macro mode, enable it to get sharp pictures.

        2) Check the glass fuse. A good fuse should be less than 1.0 ohms.

        3) Check the bridge rectifier (just below the big cap) for shorts.

        4) Check power mosfet (just right of the big cap) for shorts.

        5) Aggh. PlainBill's ISP beat me again.
        --- 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


          #5
          Re: Elo 1525L power board ptb-1218

          Updated images again

          Guys, I could get no readings on 200 ohm from any of them.
          I placed the DMM on diode like you stated and here is my findings:

          zd801 = 717
          d803 = 497
          d803 = 500
          d806 = 317 <--both directions for some reason

          KA3842A / v251c I801 = not sure how to test

          A733P / w28 Q806 = not sure how to test

          The Q803 was the s0220 SSS 4N60B
          Attached Files

          Comment


            #6
            Re: Elo 1525L power board ptb-1218

            There is power all the way to I802, C828 that connects the top portion of the board... just nothing past

            Comment


              #7
              Re: Elo 1525L power board ptb-1218

              Believe it or not, that is good news - sorta.

              Now you get to take voltage readings on I801. I'd like the voltage on each pin. Use the negative lead of the large cap (C805?) as the ground point. And try not to short anything out this time.

              If you want to get more information on what is going on here, the ON Semiconductor datasheet for this IC contains a typical application schematic (Figure 34). It's not identical, but it should be close enough.

              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


                #8
                Re: Elo 1525L power board ptb-1218

                here we are with those results

                nothing held steady for some reason... voltage all over the place....
                taken measurements with black probe on negative side of large cap (stripe side)

                1 = .00-.72 DMM set on 20
                2 = .00-.09
                3 = .64-.70
                4 = .03-.35
                5 = .01-.03
                6 = .00-.01
                7 = 11.91-13.96
                8 = .12-.69


                again the voltage was all over the DMM.... Large cap was 168.8-168.9
                Last edited by BlkSmth; 05-23-2011, 07:11 PM.

                Comment


                  #9
                  Re: Elo 1525L power board ptb-1218

                  Originally posted by BlkSmth View Post
                  here we are with those results

                  nothing held steady for some reason... voltage all over the place....
                  taken measurements with black probe on negative side of large cap (stripe side)

                  1 = .00-.72 DMM set on 20
                  2 = .00-.09
                  3 = .64-.70
                  4 = .03-.35
                  5 = .01-.03
                  6 = .00-.01
                  7 = 11.91-13.96
                  8 = .12-.69

                  again the voltage was all over the DMM.... Large cap was 168.8-168.9
                  Interesting. Check the value of R811. That senses the current through the primary of the transformer. If you haven't already done so, replace C807. Both I801 and Q803 could have been damaged, but the readings don't really support either being bad.

                  If you haven't already done so after the accident, check both D809 and D810. If either was shorted, it could account for the readings.

                  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


                    #10
                    Re: Elo 1525L power board ptb-1218

                    R811 showed .224-.225 on DMM , should I remove this component and test it? also what would be preferred setting on DMM for this?

                    C807 was replaced before incident. D809 may be shorted (both directions) on the DMM diode test. D810 seems ok. (posting from work, I forget what that reading was one direction). Interesting to me seems if I choose ground on the chassis of the monitor (not on power supply) and test lower half it's all 80.4-.80.5v on most components, nothing on the top half. But when I ground to the large cap like I did for the test of I801, the upper half tests power at 80.4-80.5v and nothing on the bottom? Why is this... I'm doing something wrong here.....

                    Comment


                      #11
                      Re: Elo 1525L power board ptb-1218

                      Originally posted by BlkSmth View Post
                      R811 showed .224-.225 on DMM , should I remove this component and test it? also what would be preferred setting on DMM for this?

                      C807 was replaced before incident. D809 may be shorted (both directions) on the DMM diode test. D810 seems ok. (posting from work, I forget what that reading was one direction). Interesting to me seems if I choose ground on the chassis of the monitor (not on power supply) and test lower half it's all 80.4-.80.5v on most components, nothing on the top half. But when I ground to the large cap like I did for the test of I801, the upper half tests power at 80.4-80.5v and nothing on the bottom? Why is this... I'm doing something wrong here.....
                      What is the color code on R811? It's in shadow in the pictures. Typically it is a .22 ohm resistor

                      Check D809 out of circuit.

                      This is a common question. To understand what is happening, several facts are important.

                      1. The nominal input voltage is 125 VAC. There are three wires coming to the monitor - live, neutral, and ground. Neutral and ground are tied together at the breaker (or fuse) box.

                      2. The live line swings from roughly +170 volts to - 170 volts (and back) 60 times a second. Thus half the time the live wire is at a higher instantaneous voltage than the neutral wire and the other half the time it is at lower voltage.

                      3. There is a bridge rectifier before the main cap. This ties the + side of the
                      large cap to whichever line is at a higher voltage, and the - side of the cap to whichever line is at the lower voltage.

                      4. this means that half the time the - side of the cap is at 0 volts and the other half of the time it is going toward or returning from -170 volts. The + side swings from 0 volts to + 170 volts.

                      5. Since the chassis is tied to ground, and ground is tied to neutral, the + side of the main filter cap is at an average of 85 volts DC with respect to ground.

                      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


                        #12
                        Re: Elo 1525L power board ptb-1218

                        Burgundy/Redish - Redish/Orange - Gold -Gold

                        Comment


                          #13
                          Re: Elo 1525L power board ptb-1218

                          Originally posted by BlkSmth View Post
                          Burgundy/Redish - Redish/Orange - Gold -Gold
                          Those aren't standard colors!! Let's agree that .22 ohms indicates the fuse is good.

                          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


                            #14
                            Re: Elo 1525L power board ptb-1218

                            Originally posted by PlainBill View Post
                            Those aren't standard colors!! Let's agree that .22 ohms indicates the fuse is good.

                            PlainBill
                            Amen to that brother :P

                            my first guess would be red/orange/gold/gold...just uncertain...
                            however if they are that color senario, you'd be correct from what i understand

                            I'll be checking that diode D809 out of circuit later tonight. I really appreciate all the help here. I have one of them Dynex LCD32 thats on this forum also, to play with next... except mine looked like the .1 ohm 1w fuse burnt (out of production got 6 coming from malaysia heheh) Thats my next tackle!

                            updates will be later tonight or tomorrow friends! ...Thanks again!

                            Comment


                              #15
                              Re: Elo 1525L power board ptb-1218

                              Update on the Resistor.... Brown/Red/Gold/Gold see image.
                              The D809 has no value either way on 200 (ohm range), on Diode Mode reading of 423 black probe on stripe side (873 backwards) Then the D810 has on 200 mode 159.7 then with Diode Mode 187 (1700+ backwards) Are these supposed to work backwards on Diode Mode?
                              Attached Files

                              Comment


                                #16
                                Re: Elo 1525L power board ptb-1218

                                Originally posted by BlkSmth View Post
                                Update on the Resistor.... Brown/Red/Gold/Gold see image.
                                The D809 has no value either way on 200 (ohm range), on Diode Mode reading of 423 black probe on stripe side (873 backwards) Then the D810 has on 200 mode 159.7 then with Diode Mode 187 (1700+ backwards) Are these supposed to work backwards on Diode Mode?
                                OK, so it's a 0.12 ohm resistor. Allowing for lead resistance, it's good.

                                Meters vary. On the diode test range mine applies 1 ma at a maximum of 2.5 volts across the leads. I'd have to look it up, but it uses less than .2 volts for resistance measurements. I'd say that those diodes should read about .2 volts forward and open in the reverse direction when tested out of circuit. I don't have a board on hand that I care to strip, but I verified that in circuit.

                                Judging by the board, D809 did get uncomfortably warm. Note that these are high speed Schottky diodes. You can't use a 1N5400 diode and expect it to work.

                                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


                                  #17
                                  Re: Elo 1525L power board ptb-1218

                                  Shall I remove D809 get value from label and replace your thinking?

                                  Comment


                                    #18
                                    Re: Elo 1525L power board ptb-1218

                                    Originally posted by BlkSmth View Post
                                    Shall I remove D809 get value from label and replace your thinking?
                                    I had assumed you had checked them out of circuit. If you haven't, do so and also check D810. They should both read open in the reverse direction for both resistance and on the diode test.

                                    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


                                      #19
                                      Re: Elo 1525L power board ptb-1218

                                      Removed them again to get actual postable readings out of circuit:

                                      D809 = SF34 Diode and reads on Diode Mode: 441 Black probe on Cathode stripe side... nothing reverse... and nothing either direction on 200, 2k, 200k

                                      D810 = SR360 Diode and reads on Diode Mode: 192 Black probe on Cathode stripe side... nothing reverse... and nothing either direction on 200, 2k, 200k

                                      Are these the values we needed, or did I set the DMM wrong?

                                      Thanks again

                                      nothing meant just a "1" or "l"
                                      Last edited by BlkSmth; 05-25-2011, 04:10 PM. Reason: Addon

                                      Comment


                                        #20
                                        Re: Elo 1525L power board ptb-1218

                                        Originally posted by BlkSmth View Post
                                        nothing meant just a "1" or "l"
                                        A multimeter ALWAYS gives a reading. "1" IS a reading. "1" on the left hand side of the multimeter means it is out of range for the chosen range. So if your multimeter is set to 200 ohms, it means the reading is greater than 200 ohms.
                                        --- 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

                                        Working...
                                        X