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Killed an EBY701

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  • Killed an EBY701

    Disassembled my old screen (2008) for a new project. Put it back together without the shell just to confirm my video source worked, plugged in the power supply and *POOF*, smoke.

    Two capacitors were blown (one on the controller board, one in the power egg) which I've replaced, but it doesn't seem to want to power on. Has anyone else been as stupid as me, and if so, did you manage to fix the screen without buying a new controller board?

  • #2
    maybe there is something else blow too. i had blown an LCD once. to find what was faulty, i had applied power to it, and followed all of its "paths" with a voltometer. i found out at what place the current was stoping, and hence the blown part . (That is, if there is a problem with the power board, but it might be usable at the cotroller as well?)


    • #3
      The controller is the power board in this case. I've gone over the board looking for other blown components, but the few resistors that looked suspicious turned out to be fine when checked with the multimeter.

      It's the old-style CCFL screen as well - I'm surprised it's lasted this long to be honest.


      • #4
        Could it be a fault or short in the screen? Maybe a blown/shorted cap or diode, wrongly connected power (wrong polarity), or pinched/shorted power & GND wires?

        Still, it's unusual for caps to blow. That suggests age (if electrolytic) or an over voltage.
        If it is aged electrolytic caps, replace all electrolytics. (Check for bulging of their tops or ends.)
        Diodes may also short with age - eg, voltage limiting Zeners or reverse-biased spike & polarity protection power diodes.


        • #5
          I'm absolutely certain I blew the board by putting the wrong polarity through it. But now I'm on the hunt for blown components. Aside from the large capacitor I replaced, all the others look good, although it's impossible to tell for the ceramic types so I may replace them just in case.

          I'm not quite sure how to trace the power flow though, as settra suggests.


          • #6
            well. if you give power to the lcd, and you put the voltometer acrros its input pins, you are supposed to see 12v. then go on the next "parallel" conenction , (logicly after the next component) and see if there is a voltage there. the "paths" will split most propably. in my case it was easy , 3 components after input. but i dont know if it would work if it was further inside... :/


            • #7
              Originally posted by Grrrmachine View Post
              ... although it's impossible to tell for the ceramic types so I may replace them just in case.
              Ceramics will be fine.

              It's only polar components that can be effected - eg, electrolytic caps (except non-polar types), diodes and semiconductor.

              Voltage tracing is okay to find blown series components (open or shorted) but is tricky for other faults.


              • #8
                I'm not having much luck here, it seems. There seems to be voltage in places all over the board, so it's certainly being distributed somehow.

                This is the board (replacement from ebay): Click image for larger version

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                Just above the transformer (big copper coil) there are two large capacitors. One of those had properly blown, so that's replaced. And during my power-tracing I put my meter across a power chip on the reverse side and got the red led to come on for a moment, before I heard a sizzling from the other side of the board...

                Seems those big blue caps (top right corner) have blown, since they're bulged and discoloured. If I'm very lucky, replacing those will fix the issue. If not...


                • #9
                  Oops - I forgot to mention (most) tantalum cap are also polarised, but I don't see any. But I count 13 electrolytics, and many semiconductors (transistors & chips) all of which may have blown, though maybe the big trannies and voltage regulator blew before the big chips...

                  IMO those top RH big blues look like ordinary non-polarised caps and should be ok - they don't bulge, they crack. Tantalums look similar but are usually color coded and should definitely have a clearly marked + or - if they are polar.


                  • #10
                    the screen does not come up at all?? not even the led in her "buttons" ??


                    • #11
                      No, absolutely nothing. I thought it might be a ribbon cable problem, but I had reconnected that about 10 times now with no change.


                      • #12
                        I was barking up the wrong tree A capacitor blew in the lilliput power egg as well as on the board, so I replaced that too, and when tested I was getting 12V through it, so I thought that was fine.

                        Just tried powering the screen with a 12V 1Amp adapter from the mains, and it powers up! So it seems I repaired the control board fine, but not the power egg.

                        Thanks for your help guys!


                        • #13
                          coool gj!!