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Daytek F19AH

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    #1

    Daytek F19AH

    Daytek F19AH this unite powers on with green light and fades to orange when not connected to computer. The back lights will not light. Changed all caps except one a 10uf@50v.. Checked the voltages as follows; across large capacitor 169v. from gr to red to the logic board 11.98v across Q13 and 14 11.98 v 9.6 v dc on T1 from center to either leg. The resistance on T101 black to white wire in infinite. Not sure what these readings meen if any thing? From what I can read this would indicate that the ac and dc is working?? Any suggestions
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    #2
    Re: Daytek F19AH

    What does it do when it's hooked up to a known good video source (might be good to check all available input types - D-sub, component, DVI, HDMI, etc.)?

    Originally posted by davg
    Changed all caps except one a 10uf@50v.
    I'm curious to know the reason this cap was left alone? If it's the short guy next to the filter cap (the big fat guy laying down) then it's a part of the startup circuit and provides critical voltages to the controller IC.

    The voltages to the logic card sound fine; have you measured the voltage to the inverter? Pictures of the logic card and inverter may yield more clues.

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      #3
      Re: Daytek F19AH

      Thanks Wrog for your post. When connected to the computer the light stays green. I didn't replace the small cap next to the big one because I didn't have a suitable replacement. Not sure where to measure the voltage to the inverter. I will post a picture of the logic board in the morning.

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        #4
        Re: Daytek F19AH

        Originally posted by davg
        Thanks Wrog for your post. When connected to the computer the light stays green. I didn't replace the small cap next to the big one because I didn't have a suitable replacement. Not sure where to measure the voltage to the inverter. I will post a picture of the logic board in the morning.
        I should pay better attention (I think I hear PB sighing somewhere); the power and inverter boards are combined.

        What are the markings on IC101 (rear side, upper center), and Q13 and Q14 (rear side, center)? Find the data sheet on IC101 and make sure the output voltage is within range, and check Q13/Q14 for shorts. Also, what are the markings on IC1 and IC4 (rear side, right)?

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          #5
          Re: Daytek F19AH

          Originally posted by Wrog
          I should pay better attention (I think I hear PB sighing somewhere); the power and inverter boards are combined.

          What are the markings on IC101 (rear side, upper center), and Q13 and Q14 (rear side, center)? Find the data sheet on IC101 and make sure the output voltage is within range, and check Q13/Q14 for shorts. Also, what are the markings on IC1 and IC4 (rear side, right)?
          Thanks Wrog the markings are very difficult to read on IC101 looks like 568415z? the 5 could be an S bottom # looks like KZA037605190?
          IC1 markings look like 129932GN top 0505A center and 13096601T bottom and on IC4 393 top E450 bottom. I have no idea where to find data sheets for these componets? I have not tested the Q13/Q14 yet still have to do some reading on testing transistors in circuit.

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            #6
            Re: Daytek F19AH

            Wondering if anything ever came of this thread/monitor? I have the same monitor but it is a F19DH...SAME POWER BOARD though. It will not power up at all. No power light or anything. Opened it and there was one bulged 470uf 25v cap. I replaced that along with the other 470uf as well as both 220uf and the 100uf but they are all 50v now. The only two I did not change were the 10uf 50v or the big filter cap beside it as I didn't have those. Still no power light or anything. Before I replaced the caps I noticed there was a steady clicking noise coming from the board when plugged in and the clicking still remains after replacing all the caps. Using one of those stethascope things for finding engine noise (it works) and I find the noise to be coming from the yellow transformer beside the large filter cap. Is that transformer supposed to make a steady but very quiet clicking noise or is that the next thing to replace? (In the first picture the big black cap behind the blue 470uf is the original one that was bulged and the first one I tried replacing. It was identical to the blue 470 thats in the pic. There were two of them.)
            Attached Files

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              #7
              Re: Daytek F19AH

              Originally posted by UserName666 View Post
              The only two I did not change were the 10uf 50v or the big filter cap beside it as I didn't have those.

              I find the noise to be coming from the yellow transformer beside the large filter cap.
              I believe the 10uF 50V cap is the startup/run cap. These little caps do not have to bloat in order to be bad. It could have high ESR (ohm) or have incorrect uF.

              The SMPS is clicking as it tries to startup.

              I suggest replacing that little cap and retesting.
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                #8
                Re: Daytek F19AH

                I shall hunt down a 10uf 50v cap. Thanks for the quick reply.

                Comment

                  #9
                  Re: Daytek F19AH

                  OK I somehow passed these before but I found two 10u-M 63 volt caps. What is 10u-M?? Will these work. The other just say 10u. Not 10u-M or 10uf.
                  Attached Files

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                    #10
                    Re: Daytek F19AH

                    Originally posted by UserName666 View Post
                    OK I somehow passed these before but I found two 10u-M 63 volt caps. What is 10u-M?? Will these work. The other just say 10u. Not 10u-M or 10uf.
                    I don't know about the markings because they are ambiguous. If you have a multimeter, you can measure the capacitance and make sure it is close to 10uF.

                    If they measure 10uF, you can use them as a test to see if the SMPS starts up, but I would use a quality cap longer term.
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                      #11
                      Re: Daytek F19AH

                      Originally posted by UserName666 View Post
                      OK I somehow passed these before but I found two 10u-M 63 volt caps. What is 10u-M?? Will these work. The other just say 10u. Not 10u-M or 10uf.
                      Those are 10uF, 63 Volt.

                      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.

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                        #12
                        Re: Daytek F19AH

                        The "M" on the cap is +/- 20% tolerance

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                          #13
                          Re: Daytek F19AH

                          I only have a digital meter and not sure how to do cap checks with it but tried the one labeled as 10u as I have never heard capacitors in anything but farads and was pretty much the same physical size/values +13 volts. Not gonna mess with the one that says u-M though.
                          The transformer still clicks like before any of the caps were changed. Only one left is the big filter cap which I know I do not have so will have to do some hunting now.

                          Comment

                            #14
                            Re: Daytek F19AH

                            Originally posted by UserName666 View Post
                            I only have a digital meter
                            If you are experienced in using a multimeter and know how to measure voltage, check to see if the secondary voltages are present. They will probably be 5V and possibly 12 or 19V DC.

                            If those are absent, see if you get 1.4 *main DC voltage across the main filter capacitor.
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                              #15
                              Re: Daytek F19AH

                              Sorry but Im not following that. This is the first time I have tried something like this and with doing it live. What I did was test at the secondary of the clicking transformer and thats 0 volts. Across the filter cap fluctuated from 158v to 162 volts on the DC setting. My filter cap is 120uf 400v.

                              Comment

                                #16
                                Re: Daytek F19AH

                                Originally posted by UserName666 View Post
                                Sorry but Im not following that. This is the first time I have tried something like this and with doing it live. What I did was test at the secondary of the clicking transformer and thats 0 volts. Across the filter cap fluctuated from 158v to 162 volts on the DC setting. My filter cap is 120uf 400v.
                                You should have seen a pulsating voltage on the DC output. Depending on the speed of your DMM, this might not be visible. The fact that the voltage across the large cap is fluctuating, I would suspect either the large cap is bad, or the diode on the output of the SMPS transformer is shorted.

                                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: Daytek F19AH

                                  Originally posted by UserName666 View Post
                                  Sorry but Im not following that. This is the first time I have tried something like this and with doing it live. What I did was test at the secondary of the clicking transformer and thats 0 volts. Across the filter cap fluctuated from 158v to 162 volts on the DC setting. My filter cap is 120uf 400v.
                                  Assuming your outlet voltage is 115VAC: 115x1.4= 161 Volts DC

                                  You were asked to check for 5 and 12 volt output. Looking at your second photo, next to to the large yellow transformer and between the heatsinks looks like a 6 prong plug. Look to see if any of those prongs are labelled 5V, 12V, ground, etc. With your meter set to DC and both boards and backlights connected, power on the monitor and check for the 5V and 12V voltages. I suspect you'll read 0 volts, since the transformer secondary is putting out 0V.
                                  Last edited by jetadm123; 08-30-2010, 10:16 PM.

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                                    #18
                                    Re: Daytek F19AH

                                    Wondering what the significance of 1.4 is or where it comes from?? Trying to learn something as I go here and not just play musical chairs with the components lol

                                    As for the 6 pin connector it is indeed 0 volts. - lead on middle top gnd pin and + across all others 0 volts. Same with the middle bottom gnd pin. That was tested with live power. (Transformer still clicking)

                                    Diode test WITHOUT live power and Diodes still in the board. DMM set to diode.
                                    Blue (By filter cap) - .491v Reverse leads = 0v
                                    Red (By transformer) - .491v Reverse leads = 1.643v
                                    Attached Files

                                    Comment

                                      #19
                                      Re: Daytek F19AH

                                      From post #36 in the BENQ T905 post regarding diodes:
                                      "Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L."

                                      So would that mean that the diode giving me a reading of 1.643v is damaged??

                                      Comment

                                        #20
                                        Re: Daytek F19AH

                                        Originally posted by UserName666 View Post
                                        From post #36 in the BENQ T905 post regarding diodes:
                                        "Test them with your diode setting. One way should measure 0.4 to 0.7V. Reserve and the other way should measure "1" or 0L."

                                        So would that mean that the diode giving me a reading of 1.643v is damaged??
                                        If the diode were out of circuit then that reading would be a worry. In-circuit the reading will be affected by other componentry. Without a schematic it's hard to give a 100% guarantee but it is credible.
                                        Friends don't let friends buy Samsung ....

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