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Daytek F19AH

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    #41
    Re: Daytek F19AH

    Okay, it looks like Q102 is a general purpose NPN transistor, PMBS3904. Spec sheet below. Pin 5 of IC101 is basically used to shut down the power supply in case of over temperature. Since a thermistor is not being used here like it is in the pdf schematic, the temperature function is not being used. From the IC101 specs, it looks like pin 5 has to be held at above .65 Volts to prevent power supply shutdown. Once it drops below .62 volts the supply will shutdown. With the monitor on can you measure the voltage of pin 5. If it's going below and above .62V, shut off the monitor and perform a short circuit check on Q102 using the numbering config on the spec sheet and retiredcaps instructions at this link:

    https://www.badcaps.net/forum/showth...ng+transistors

    I'm off to bed.
    Attached Files

    Comment

      #42
      Re: Daytek F19AH

      I've got a wild idea. With the boards hooked up the same way they were for the other voltage tests but with power off, measure the resistance across C122. It's on the back side of the board, close to the output connector.

      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

        #43
        Re: Daytek F19AH

        Originally posted by retiredcaps View Post
        To test for shorts on a transistor, test the following with ohms.

        pin 1 to pin 2
        pin 1 to pin 3
        pin 2 to pin 3

        If anything reads less than 50 ohms, it suggest a possible short.
        lol I had a feeling it was gonna come to something like this. Can these resistance checks be made while it is still in the board?? I have a good feeling I won't be able to solder that small.

        Originally posted by jetadm123 View Post
        Okay, it looks like Q102 is a general purpose NPN transistor, PMBS3904. Spec sheet below. Pin 5 of IC101 is basically used to shut down the power supply in case of over temperature. Since a thermistor is not being used here like it is in the pdf schematic, the temperature function is not being used. From the IC101 specs, it looks like pin 5 has to be held at above .65 Volts to prevent power supply shutdown. Once it drops below .62 volts the supply will shutdown. With the monitor on can you measure the voltage of pin 5. If it's going below and above .62V, shut off the monitor and perform a short circuit check on Q102 using the numbering config on the spec sheet and retiredcaps instructions at this link:

        https://www.badcaps.net/forum/showth...ng+transistors

        I'm off to bed.
        Re: Testing with monitor on for the 5 volts can't happen as it won't power up at all.

        Originally posted by PlainBill View Post
        I've got a wild idea. With the boards hooked up the same way they were for the other voltage tests but with power off, measure the resistance across C122. It's on the back side of the board, close to the output connector.

        PlainBill
        I have been doing the tests with the power board out from the rest of the monitor. Got tired of installing it/removing it. I was gonna wait for the transformer click to stop before hooking it all back up.
        Resistance across C122 in circuit with no voltage with power board removed from monitor is 25.9ohms one way and 27.1ohms reversing the leads.

        Comment

          #44
          Re: Daytek F19AH

          Originally posted by UserName666 View Post
          Can these resistance checks be made while it is still in the board??
          Yes, you can do the tests in circuit. If the readings look suspicious, then you will have to desolder to be 100% sure.

          PS. I'm planning to update the guide in a few weeks with some of the feedback I have gotten.
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            #45
            Re: Daytek F19AH

            Q102 reads as follows according to the pic I added (In circuit - No live power)
            1-2 = 11.80 Mohms
            1-3 = 9.97 Kohms
            2-3 = 11.77 Mohms
            Attached Files

            Comment

              #46
              Re: Daytek F19AH

              Originally posted by UserName666 View Post
              I have been doing the tests with the power board out from the rest of the monitor. Got tired of installing it/removing it. I was gonna wait for the transformer click to stop before hooking it all back up.
              Resistance across C122 in circuit with no voltage with power board removed from monitor is 25.9ohms one way and 27.1ohms reversing the leads.
              OK, scratch that idea. I was thinking in terms of a short (or low resistance) across the output.

              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

                #47
                Re: Daytek F19AH

                Originally posted by UserName666 View Post
                One thing I should have mentioned right of the top is this monitor was used in a poorly ventilated cabinet and all of the sudden just went out and you could faintly smell burnt electronics. The poorly ventilated cabinet makes me think this was an overheat issue.

                Since you mentioned that you got a whiff of the "magic smoke", can you please post two of your cool pictures of the entire board, both top and bottom.

                Comment

                  #48
                  Re: Daytek F19AH

                  Done. These are the highest megagpixel setting my camera can do.
                  Attached Files

                  Comment

                    #49
                    Re: Daytek F19AH

                    There is a possiblity that acer 1914bm uses the same power board as this Daytek. You can search acer 1914bm service manual to see if there is one with schematics.

                    I got this idea from the 0509d1248 designation (right above the li shin) on the board.
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                      #50
                      Re: Daytek F19AH

                      This is sort of a weird design where there's only one dual diode pak (Q1 in the pdf file) that supplies 12 volts for everything. Normally, you have two separate paks, one to supply 12V to the inverter and the other to supply 5V to the logic board and LCD panel. Looking at your photo, I believe the diode pak on your board is the one mounted to the heatsink at the left. It usually has a symbol of two diodes connected head to head stamped on it. Please supply the part # and with power off try performing a short circuit check on it in circuit.
                      Last edited by jetadm123; 09-01-2010, 11:05 AM.

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                        #51
                        Re: Daytek F19AH

                        I should have asked first but I hope these tests can be done in-board because thats the way I did it.

                        The one circled in YELLOW on the heatsink by the filter cap is:
                        1-2 = Starts at 41 Kohm rises to about 400 Kohm then jumps to about 1.2 Mohm and keeps rising. Reverse leads 0 Mohms
                        1-3 = 86.1 kohm reverse leads 81.2 Kohm
                        2-3 Starts at 18.5 Mohms and drops. I stopped testing at 12 Mohms. Reverse leads 0 Mohms

                        The one circled in RED by the cluster of caps is:
                        1-2 = 27.1 ohms reverse leads 26 ohms
                        1-3 = 00.3 ohms reverse leads 00.3 ohms
                        2-3 = 27.1 ohms reverse leads 26 ohms

                        Part #'s are visible in pic 2 & 3. I didn't know if that was a letter F or a company logo.
                        Attached Files
                        Last edited by UserName666; 09-01-2010, 01:21 PM.

                        Comment

                          #52
                          Re: Daytek F19AH

                          As for the service manual I found one for a 1914 but not 1914bm specific. The powerboard is not a match.
                          Attached Files

                          Comment

                            #53
                            Re: Daytek F19AH

                            Originally posted by UserName666 View Post
                            The one circled in RED by the cluster of caps is:
                            1-2 = 27.1 ohms reverse leads 26 ohms
                            1-3 = 00.3 ohms reverse leads 00.3 ohms
                            2-3 = 27.1 ohms reverse leads 26 ohms

                            Part #'s are visible in pic 2 & 3. I didn't know if that was a letter F or a company logo.
                            0.3 and 27 ohms suggests this is shorted or bad.

                            edit: Datasheet is at



                            You will have to desolder this component and test out of circuit to verify it is shorted.

                            F, I think, is Fairchild.
                            Last edited by retiredcaps; 09-01-2010, 01:27 PM.
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                              #54
                              Re: Daytek F19AH

                              Originally posted by retiredcaps View Post
                              0.3 and 27 ohms suggests this is shorted or bad.

                              edit: Datasheet is at



                              You will have to desolder this component and test out of circuit to verify it is shorted.

                              F, I think, is Fairchild.
                              OK & ya know what...The one with 00.3 ohm reading (red) is DIRECTLY BESIDE the capacitor that was bloated by like less than 2mm. I'll get to the desoldering in a little bit and get back w/ he readings

                              Comment

                                #55
                                Re: Daytek F19AH

                                Originally posted by UserName666 View Post
                                OK & ya know what...The one with 00.3 ohm reading (red) is DIRECTLY BESIDE the capacitor that was bloated by like less than 2mm. I'll get to the desoldering in a little bit and get back w/ he readings
                                Is it possible that your replacement capacitor soldering is touching this component? That would cause false readings.
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                                  #56
                                  Re: Daytek F19AH

                                  No I meant 2mm close on the top of the board but looking underneath the middle pin of the rectifier IS connected to the cap that was bloated.

                                  Rectifier in blue and the capacitor that bloated is in red.
                                  Attached Files

                                  Comment

                                    #57
                                    Re: Daytek F19AH

                                    Originally posted by UserName666 View Post
                                    No I meant 2mm close on the top of the board but looking underneath the middle pin of the rectifier IS connected to the cap that was bloated.

                                    Rectifier in blue and the capacitor that bloated is in red.
                                    Okay, soldering all looks good. No bridges. I suggest you desolder the component and test out of circuit.

                                    If it is bad, a replacement is available at digikey for just over $1.
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                                      #58
                                      Re: Daytek F19AH

                                      OK I pulled the STPS10H100CT from the board and it reads:

                                      1-2 = Starts at 30 Mohm and continuously drops rapidly-reverse leads- Starts at 32 Kohm and drops slowly.

                                      1-3 = Starts at 26 Mohm and drops rapidly -reverse leads- Starts at 36Mohm and drops rapidly

                                      2-3 = Starts at 30 Mohm and drops rapidly -reverse leads- 40.1 Kohm (steady)

                                      Comment

                                        #59
                                        Re: Daytek F19AH

                                        Originally posted by UserName666 View Post
                                        OK I pulled the STPS10H100CT from the board and it reads:
                                        There is another component right by this STPS10H100CT. I can't see it from the angle of the pictures, but it has 02 and the end. I think it is a diode D102?

                                        1) what is it?
                                        2) if it is a diode, do a diode check with your multimeter. This component could be shorted? This would explain why pin 1-3 on the STPS10H100CT in circuit, but measure non shorted out of circuit.

                                        STPS10H100CT is good out of circuit from your measurements.
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                                          #60
                                          Re: Daytek F19AH

                                          I'm not sure what it is but it is labeled L102. D108 is what I just took out.

                                          This boards also has an L107,L105 and L108 surrounding the Filter cap. Not that has anything to do with anything. Just not sure what the "L" is.
                                          Attached Files

                                          Comment

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