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    #1

    daytek TV - kinda like 2 secs to black?

    I didn't have very much luck on my first tv repair but i'm not giving up I have bought another damaged tv and this time the insides look very simple and somewhat familiar

    Model;
    Daytek DK 321A
    32 inch

    The symptoms;
    It almost seems like 2 seconds to black, I don't have a video fed into it so I am just using the logo “no video” that is floating around on screen like a windows screen saver so when I say “picture” this is what I am referring to.
    It works fine for about 2 minutes then the logo flashes off then back on again. The longer I keep the tv on for the faster it keeps blinking on and off. I thought this was 2 seconds to black which I have seen before so although I couldn't see any bloated caps, I went and recapped the power supply. This didn't make any difference at all.

    Here is a video of the symptoms

    http://www.youtube.com/watch?v=wALSmTLc6I4
    Attached Files
    Tags: None
    #2
    Re: daytek TV - kinda like 2 secs to black?

    Originally posted by scampo77 View Post
    I didn't have very much luck on my first tv repair but i'm not giving up I have bought another damaged tv and this time the insides look very simple and somewhat familiar

    Model;
    Daytek DK 321A
    32 inch

    The symptoms;
    It almost seems like 2 seconds to black, I don't have a video fed into it so I am just using the logo “no video” that is floating around on screen like a windows screen saver so when I say “picture” this is what I am referring to.
    It works fine for about 2 minutes then the logo flashes off then back on again. The longer I keep the tv on for the faster it keeps blinking on and off. I thought this was 2 seconds to black which I have seen before so although I couldn't see any bloated caps, I went and recapped the power supply. This didn't make any difference at all.

    Here is a video of the symptoms

    http://www.youtube.com/watch?v=wALSmTLc6I4
    A good description of the problem, let's see if we can troubleshoot this logically. But first, a hint.

    One thing that is missing from the pictures is an overall layout shot, and a picture of the inverter. Also, quite often clues can be found at the edges of the board, so cropping pictures too closely isn't helpful.

    NOW, working with what we do have, I see three output connectors from the power supply, two of them in use. Possibly one goes to the inverter, one goes to the main board. Or one may go to the main board, the other to an audio amp, and the inverter gets it's power from the motherboard.

    What you are looking for are the control lines to the inverter; often labeled BL_ON and BRIGHT. And what you want to do is measure the voltage on thBL_ON line as the display flashes on and off. Also check the power to the inverter, it can avoid a lot of wasted time.

    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

      #3
      Re: daytek TV - kinda like 2 secs to black?

      ehm... 2nd pic, the 3 caps on the top left

      Panasonic HFG ? general purpose caps in a PSU? :O

      Comment

        #4
        Re: daytek TV - kinda like 2 secs to black?

        im not too sure how to check the power to the inverter board

        i did measure all the pins going to it and i think the one you mentioned, the BL and Bright are the ones on the right side of that picture. they are both rock solid at their voltages. the 24v is fluctuating in time with the on/off of the screen and they move from 24.22v to 24.18 its not much movement but i figured it was worth mentioning

        the bulbs are staying on super bright and not dimming at all

        as for my caps, i know i know but i am still very much just learning here and i cant wait for MCM mailing me 3 caps a time. i am working off of what resources i have here at home and at the local supply store. if i can manage to get this one working i will replace these caps with quality ones before doing something with it. right now i am operating on the assumption that they wont be fixed and will be thrown out.
        Attached Files

        Comment

          #5
          Re: daytek TV - kinda like 2 secs to black?

          PlainBill has more experience in this area, but I believe the INV_CTL is the one to observe when the set/display goes off. Once the display goes off, measure that pin. If the voltage drops from 3.3V to 0V DC, it implies something on the main/logic board is turning off the backlight.

          If the backlight goes off and the INV_CTL stays at 3.3V DC, then it implies something is wrong on the inverter board.

          Please post a clear focused picture of the inverter board. In addition, post another close up picture of just one inverter transformer (including the white/pink wires) so we can read/see the transformer part number.

          The closeup pic will help identify which are the secondary inverter transformer pins. Once identified, you will measure the resistance of all of them to see if one is bad. The secondaries are pins "feeding into" pink/white wires usually through some capacitor.
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          Comment

            #6
            Re: daytek TV - kinda like 2 secs to black?

            i can post more pictures but while the screen is shutting off/on the INV_CTL is rock solid at ~3.25 dcv and the back lights arent shutting off or flickering

            doesnt this mean that the inverter board/bulbs are good?

            Comment

              #7
              Re: daytek TV - kinda like 2 secs to black?

              So the backlights STAY on at all times, just the picture itself goes away? This sounds like a logic board issue.
              Originally posted by PeteS in CA
              Remember that by the time consequences of a short-sighted decision are experienced, the idiot who made the bad decision may have already been promoted or moved on to a better job at another company.
              A working TV? How boring!

              Comment

                #8
                Re: daytek TV - kinda like 2 secs to black?

                Originally posted by scampo77 View Post
                i can post more pictures but while the screen is shutting off/on the INV_CTL is rock solid at ~3.25 dcv and the back lights arent shutting off or flickering

                doesnt this mean that the inverter board/bulbs are good?
                I suggest hooking up a source like a dvd player versus "no signal".
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                  #9
                  Re: daytek TV - kinda like 2 secs to black?

                  +10000 you might just be chasing nothing here. Recheck it with a good video signal inputted.

                  Comment

                    #10
                    Re: daytek TV - kinda like 2 secs to black?

                    i put a video source to it and i am having very similar symptoms. from what i know about these things i would think this problem is something in the logic board, i did however include pictures of the HV transformers.
                    Attached Files

                    Comment

                      #11
                      Re: daytek TV - kinda like 2 secs to black?

                      If your backlights are staying on throughout, then let's test the voltage regulators on the logic/main board.

                      I circled 9 voltage regulators. They should have part numbers like AL1117-33. The suffix, 33, indicates the output voltage. That is, 3.3V DC.

                      List all part numbers and the DC voltages on each pin (don't measure the tab pin). Use a ground screw on the logic/main board for your black probe.

                      Voltage regulators have a 1% tolerance.
                      Attached Files
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                        #12
                        Re: daytek TV - kinda like 2 secs to black?

                        I'm so sorry for the lateness of this reply, this TV has been sitting here apart this entire time and I'm still interested in learning to fix these things. its just that work picked up and after working all day i didn't feel like coming home to a broken TV to fix

                        i did my best measure and post all the part numbers and measurements. i measured the tabs even tho i was instructed not to. i figured since i was in there i may as well

                        i think i noticed one that might be a problem the 2x LD18 on the cluster of 4 on the right hand side although they have the same part number they have different measurements. but they also have different tab voltages too.

                        also the regulator on the bottom right hand corner (AZ7809D) fluctuates with the flickering on and off of the TV. its not much but its still note worthy, as the rest were rock solid. it fluctuates from 11.75~11.83

                        thanks again for all the help i hope this thread is still alive and someone is willing to help out
                        Attached Files

                        Comment

                          #13
                          Re: daytek TV - kinda like 2 secs to black?

                          hmm...
                          if LD33 = 3.3V and LD18 =1.8V, the top right LD18 is supposed to put out 1.8V, but instead it's almost 3.3V :O
                          and the bottom left LD18 is pretty low at 1.7V

                          the AZ780x seem to be all OK (the last digit is the voltage it's supposed to put out)

                          Comment

                            #14
                            Re: daytek TV - kinda like 2 secs to black?

                            should i order new ones? is there anything else i should check before ordering?

                            Comment

                              #15
                              Re: daytek TV - kinda like 2 secs to black?

                              i'm not a TV expert :/
                              that's just what i noticed... 4 eyes see more than 2 and stuff..

                              better wait for plainbill or retiredcaps

                              Comment

                                #16
                                Re: daytek TV - kinda like 2 secs to black?

                                There are a couple of anomalies here. I'd suggest verifying the part numbers of each of the 4 regulators on the right side. I'm also mildly curious about the source of the 3.74 volts on the one with the 1.7 volts out.

                                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 TV - kinda like 2 secs to black?

                                  from my notes i took i missed 2 important values to the right of the decimal. regulator F at 1.7 is in fact 1.798. sorry about that i updated the new picture and gave them locations as well.

                                  also regulator E has changed in value it is now 1.906 it is possible i measured it wrong the first time around but it seems unlikely. all i know is now its at 1.9 now.

                                  i see what you mean about regulator F power source the rest are pretty solid at 5v does the fact that im still getting 1.8v on the other side negate the bad source voltage?

                                  i double checked D,E,F,G and all the part numbers are correct to my original post. there are additional numbers if you like but i suspect they are manufacturing codes.
                                  Attached Files

                                  Comment

                                    #18
                                    Re: daytek TV - kinda like 2 secs to black?

                                    now "E" is too high... 1.90V instead of 1.80
                                    all the others seem to be pretty much dead on.
                                    only "A" is an exception, as it's probably an adjustable voltage regulator.. (or is there anything behind the "AZ1117D"? like AZ1117D-18 for example)

                                    Comment

                                      #19
                                      Re: daytek TV - kinda like 2 secs to black?

                                      Originally posted by scampo77 View Post
                                      also regulator E has changed in value it is now 1.906 it is possible i measured it wrong the first time around but it seems unlikely. all i know is now its at 1.9 now.
                                      E is high. It should be 1.8 +/- 1%.

                                      So 1.8 x 1.01 = 1.818.
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                                      Comment

                                        #20
                                        Re: daytek TV - kinda like 2 secs to black?

                                        should i go ahead and order just this regulator? or is there any other contributing factors that would cause something like this to fail ie, cap or resistor close to it or in the same circuit.

                                        or should i just replace that one and see what happens?

                                        Comment

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