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ADi T8053 LCD Color Terminal - PSU output high at startup

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    #1

    ADi T8053 LCD Color Terminal - PSU output high at startup

    I have here a thin terminal PC, seems to run Windows CE or some variation...
    It's basically a small Geode based PC built into the back of an LCD monitor.

    The front displays the logo "ADi"

    On the back, the sticker says

    Product Name: T8053 LCD Color Terminal
    Model Number: WT-500H
    Description: TD-551W


    When I first got it, I couldn't get it to startup (seemed totally dead, press power button, nothing happens, not even an LED)

    After pulling it apart I notice there has been work done on the PSU, some components have fresh solder (though I can't tell if components are new)

    After putting it back together it seems to work, but I am worried about the 12v line.

    This PSU seems to be similar to ATX (wiring colours and voltages are the same, green wire for PS_ON but no PWR_GOOD and it lacks 3.3v rail)

    At power-on, the 12v rail jumps up to 22v and then falls back to 12v faster and stays there (I measured with DMM so it may go higher than this) 5volt rail seems fine. 5v standby also seems fine (though maybe a little low, 4.78v)

    I suspect the PSU to be faulty in some way, especially as it did not even power up the first time I tried it

    However since no actual damage seems to be done to the components, I considered the possibility that they are just using a really badly designed PSU and have also included protection circuitry to limit the initial overvoltage condition (I know that is stupid but I'm sure someone's seen stupider designs than that)


    If anyone has experience with this model, would be great to hear, or any other thoughts on the matter. If it is a fault, what would I be looking for?
    Attached Files
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn
    Tags: None
    #2
    Re: ADi T8053 LCD Color Terminal - PSU output high at startup

    Anyone got any ideas at all?
    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
    -David VanHorn

    Comment

      #3
      Re: ADi T8053 LCD Color Terminal - PSU output high at startup

      try getting rid of the crapcaps (jamicon in PSU and the garbage around the cpu) ?

      the NCCs near the secondary side heatsink of the psu may be cooked aswell.
      who knows how long this thing has been running.. look at the discoloration..

      Comment

        #4
        Re: ADi T8053 LCD Color Terminal - PSU output high at startup

        One of those Jamicons looks 'wrong'. The sleeving is too thick at the top.

        Comment

          #5
          Re: ADi T8053 LCD Color Terminal - PSU output high at startup

          Once the thing has started it does run, so the motherboard caps are probably OK (or at least not causing the PSU issue)

          Powering up the PSU without being connected to the motherboard results in the high voltage problem as well as when it is connected, so I think the PSU is solely responsible for that issue

          I agree that Jamicon looks odd but I doubt a slightly longer sleeve would be an issue.

          However I agree with Scenic. Those NCC are actually of a series (KME) which aren't made anymore, so they're definitely old!

          Will pull them and test ESR, but actually both the Jamicons and NCCs are general purpose series and the datasheets of course show no indication of what ESR should be, though. What do you think ESR should be in this case?

          Can bad capacitors on the outputs actually cause such a huge voltage swing like this though?
          "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
          -David VanHorn

          Comment

            #6
            Re: ADi T8053 LCD Color Terminal - PSU output high at startup

            There's an issue with Bestecs where bad caps will cause the 5VSB to go through the roof...

            Comment

              #7
              Re: ADi T8053 LCD Color Terminal - PSU output high at startup

              Well that's what I was getting at, if the faulty capacitor causes the output to go high, wouldn't it stay high?

              In my case, the output goes high initially and then comes back down to normal voltage.
              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
              -David VanHorn

              Comment

                #8
                Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                Good point, does it come back down regardless of load?

                Comment

                  #9
                  Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                  It comes back to normal with and without the motherboard etc attached, so I guess so.

                  This is what made me think that maybe it was supposed to do that (!) Especially since nothing went up in smoke either... Perhaps the inverter or LCD panel needs an extra kick to get started and they've added protection against this high voltage to the motherboard... but without any kind of information on the PSU...

                  Also the output capacitors are rated for 25v and 35v... it's all rather suspicious...
                  "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                  -David VanHorn

                  Comment

                    #10
                    Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                    Maybe it is supposed to do that.

                    Either way, I would kick the old caps out and replace with new low ESR. It can't hurt, they're cheap to replace and if they don't make a difference, you at least know that they aren't the problem

                    Comment

                      #11
                      Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                      I'm a bit wary of doing that though, low ESR where normal ESR is expected can cause problems too, right?
                      "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                      -David VanHorn

                      Comment

                        #12
                        Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                        It can do I think, not that I've run into that problem yet.

                        Comment

                          #13
                          Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                          Originally posted by Agent24
                          This is what made me think that maybe it was supposed to do that (!) Especially since nothing went up in smoke either... Perhaps the inverter or LCD panel needs an extra kick to get started and they've added protection against this high voltage to the motherboard... but without any kind of information on the PSU...
                          Kind of hard to say without a shot of the under side of the PSU board.
                          It could be that the PSU was not designed to get feedback from the 12v rail and that's why you might be seeing it go high voltage without shutting off the PSU. I just fixed a monitor with a PSU board that was designed like this where only the 5v rail was used for feedback. Turned out that the cap on the 5v rail was bad which caused the regulation of the whole PSU to go amok (12v rail was at 24v!). Original cap on the 5v rail was general purpose 85C. I used a low ESR one and lo-and-behold the 12v rail came down to 16v (see this thread for more details). It really shouldn't be a problem to use low ESR caps, as long as you don't go overboard. Something like Panasonic FC, Chemicon KY, and Nichicon PW should be perfect for this application.

                          By the way, what are the numbers on top of the two 8-pin ICs?

                          Comment

                            #14
                            Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                            The IC numbers are:

                            By the line filter: KA3842B (C032C)
                            The other one: 5H0165R (S223)

                            Will get back with a photo of the underside later on...
                            "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                            -David VanHorn

                            Comment

                              #15
                              Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                              Here are the photos of the underside... hopefully they are of some use to you.
                              Attached Files
                              "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                              -David VanHorn

                              Comment

                                #16
                                Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                                Thanks.
                                From the pictures, it looks like both the 5v and 12v rail are designed to give feedback to the PSU, which is good. The fact that the 12v rail spikes so high still concerns me, though. How long does is stay high? Just a second? 5 seconds? more/less?

                                Comment

                                  #17
                                  Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                                  I think total time to start, rise to ~22v and fall back to 12v is only a few seconds
                                  I'll have to do another test though because I can't remember for sure...
                                  "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                  -David VanHorn

                                  Comment

                                    #18
                                    Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                                    Today I pulled the big capacitors on the output and measured ESR, which was 0.08 for the worst and 0.04 for the best.

                                    To me this seems OK, but I will let someone else answer that.

                                    (If anyone is still subscribed to this thread!)

                                    Then, I realised I was going to re-test and see how long the rail was high. Guess I have to put the damn things back in again!
                                    "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                    -David VanHorn

                                    Comment

                                      #19
                                      Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                                      I believe it's your multimeter overshooting rather than the PSU being bad.
                                      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

                                        #20
                                        Re: ADi T8053 LCD Color Terminal - PSU output high at startup

                                        Originally posted by Th3_uN1Qu3 View Post
                                        I believe it's your multimeter overshooting rather than the PSU being bad.
                                        Can you explain how that is so?

                                        I can do the exact same thing with a standard ATX PSU and the voltage just goes straight to 12 volts and stays there.
                                        "Tantalum for the brave, Solid Aluminium for the wise, Wet Electrolytic for the adventurous"
                                        -David VanHorn

                                        Comment

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