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Neoware Thin Client Trouble

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    #1

    Neoware Thin Client Trouble

    I have been repairing the power supplies in about 100 Neoware Eon 5000. I've gone through 61 of them thus far, most of them when powered up the power light blinks and you can hear a clicking sound from the power supply....those are a simple recap....anywhere between 1 and 8 caps replaced on each unit and they fire up like new.....however, I have 11 units that when powered up do nothing at all. I dug into one of these replaced all the caps that have been blowing on the other units, replace the + voltage regulator, the - voltage regulator, and the Fairchild Power Switch.....and still no power......if the power supply is swapped out with a known good unit....it works so the problem is in the power supply somewhere.....any thoughts???


    Heres a photo of the unit if that helps



    Thanks for any input in advance,
    Paul
    Tags: None
    #2
    Re: Neoware Thin Client Trouble

    uhm... what about the fuse...?

    Comment

      #3
      Re: Neoware Thin Client Trouble

      well, I don't see anything here labeled "fuse" I'm just an underpaid guy with an expensive solder rework station who backward engineered repair work. I have just know started to understand caps and thier values. Any chance you can tell where a "fuse" is in that picture?

      Paul

      Comment

        #4
        Re: Neoware Thin Client Trouble

        Don't start cutting just yet, as someone here might have a better idea where it is than I do. I think the fuse might be mounted vertically encased by those rubber sleeves. but they might be resistors too. I'm not 100% sure, and with the quality of your picture, I can't be 100% sure
        Attached Files
        Cap Datasheet Depot: http://www.paullinebarger.net/DS/
        ^If you have datasheets not listed PM me

        Comment

          #5
          Re: Neoware Thin Client Trouble

          directly above the white mains connector..

          Comment

            #6
            Re: Neoware Thin Client Trouble

            If the fuse checks OK, check the line filter just left of the white main power connector. It has two coils, one for line and one for neutral. Sometimes the thin wire used in the windings burns open before the fuse blows. I have seen this on several small power supplies.
            Old proverb say.........If you shoot at nothing, you will hit nothing (George Henry 10-14-11)

            Comment

              #7
              Re: Neoware Thin Client Trouble

              If the fuse and line filer are ok, it could be that the pwm/controller is not giving proper signal to the Fairchild switcher due to the 2 small electrolytic caps (one next to the pwm/controller and the other one next to the switcher) going bad. Try changing those 2 small caps with equivalent or better caps and see if the PSU comes alive.
              Lastly, if you hear clicking noises, check the 2 rectifying diodes on the secondary side.

              Comment

                #8
                Re: Neoware Thin Client Trouble

                just above the white main connector the PCB reads F1....I made the assumption that was the fuse and changed it......I had also gone over some of the work that came back from the repair shop and noticed that the line filter had been changed on one of them so I tried that as well (no luck) so I seem to be down to those 2 small caps.

                Paul

                Comment

                  #9
                  Re: Neoware Thin Client Trouble

                  In the picture I see two transformers: the big one and the smaller near a IC.
                  Has this PSU an auxiliary output? Is the Fairchild a simple PowerMos or it is an integrated Power Switch?
                  If it has an auxiliary output maybe this part is faulty.

                  I see also a yellow component with the label OK on the top ner the input filter, is this one a relay? if it is, you can check if it is working.
                  In some PSU there is a relay that short the input resistor limiting the inrush current at power up. If the relay is broken, maybe the power resistor is broken too because it is not dimensioned to support the input current for long time.

                  If you have a DMM you can check if there is voltage on the input bulk capacitor to be sure that the energy is the power switch from the input, in this way you can be sure about input circuit status.

                  With a DMM you can also check the output rectifiers, like nomaka suggested, if one is shorted the PSU can't start.

                  Ciao
                  Gianni
                  Last edited by Gianni; 03-08-2009, 02:16 PM.
                  "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
                  H. J. Brown

                  Comment

                    #10
                    Re: Neoware Thin Client Trouble

                    If there is a MOV in there it may be toast.
                    Mann-Made Global Warming.
                    - We should be more concerned about the Intellectual Climate.
                    -
                    Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
                    - Dr Seuss
                    -
                    You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                    -

                    Comment

                      #11
                      Re: Neoware Thin Client Trouble

                      to me the thing right besides the white AC connector (the one with the visible windings) looks like the relay.
                      "Every normal man must be tempted at times to spit on his hands, hoist the black flag, and begin slitting throats." - H.L. Mencken

                      Comment

                        #12
                        Re: Neoware Thin Client Trouble

                        I'm going to take a shot in the dark here and say if it's not the fuse or a startup resistor you have a PWM IC failure on your hands.

                        It's probably that 4 pin dip.
                        Elements of the past and the future combining to make something not quite as good as either.

                        Comment

                          #13
                          Re: Neoware Thin Client Trouble

                          Gianni said
                          I see also a yellow component with the label OK on the top ner the input filter, is this one a relay?
                          that is a CARLI MPX CAPACITOR numbers on the side are .33K275V-X2 MPXGMF 40/100/21 250V~

                          I'm guessing the .33 is the micro farad?

                          Paul

                          Comment

                            #14
                            Re: Neoware Thin Client Trouble

                            Yes .33 uF or if you prefer 330nF. This is an X2 cap for EMI filtering.

                            Have you any progress on troubleshooting this PSU?

                            Ciao
                            Gianni
                            "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
                            H. J. Brown

                            Comment

                              #15
                              Re: Neoware Thin Client Trouble

                              well it's 15 power supplies that display the same symptoms.....I'm starting to think it might be one of the 4 Zeners on this board....well at least I think they are zeners the board is marked ZD1 ZD2....and so on....but I can hardly read the markings on them.....under magnification I came up with 18 on one side and a 2 on the other but that doesn't seem to match what I have found on the internet for zener markings....these are very small diodes with a black stripe on one end of what looks like a glass bubble the inside of this diode looks redish in color.....I guess what might help the most is information on how I could use a DMM to test some of these components if thats possible.......

                              At this point I have saved 75 units and I have the 15 that need something other than caps......so if I were to scrap these 15 I am still way ahead of the game....but I would still like to fix them just for experience. I have checked the line filter and it has continuity on both wires and the fuse is intact....the clicking I have heard in some of these is the onboard speaker so I don't thik the problem is in the rectifying diodes on the left side there.

                              any and all suggestions are welcome,
                              Paul

                              I know for most of you this is a real stupid question....but what is a PWM

                              Comment

                                #16
                                Re: Neoware Thin Client Trouble

                                If you have to check a zener, the first thing is to measure if it is shorted.
                                With a DMM you put the red probe on the anode (A) and black on cathode (K) and you should have 0.7V. If you reverse the probe the DMM should read open circuit.

                                To check what value it is and if it works you have to feed it with at least 5~10mA.
                                For instance in your case you can connect a 120Ohm resistor to the zener and then you can feed the circuit with a 24V. If the zener is OK you should read 18V between anode and cathode.
                                Zener diode have tolerance and the voltage depends on the working parameter so you could measure something little different from 18V let say 17.4V or 18V.

                                Here better schematic and explanation.

                                Hope it helps.
                                Gianni
                                Attached Files
                                Last edited by Gianni; 03-14-2009, 04:38 AM. Reason: Typo
                                "In the confrontation between the stream and the rock, the stream always wins...Not through strength, but through persistence."
                                H. J. Brown

                                Comment

                                  #17
                                  Re: Neoware Thin Client Trouble

                                  PWM = Pulse Width Modulation
                                  http://en.wikipedia.org/wiki/Pulse-width_modulation

                                  The pulses are used to turn Transistors, MOSFETs, IC chips, etc on-off.
                                  The wider the 'on' pulse the longer it's 'on'.
                                  Same-same for off.
                                  Last edited by PCBONEZ; 03-14-2009, 05:12 AM.
                                  Mann-Made Global Warming.
                                  - We should be more concerned about the Intellectual Climate.
                                  -
                                  Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind.
                                  - Dr Seuss
                                  -
                                  You can teach a man to fish and feed him for life, but if he can't handle sushi you must also teach him to cook.
                                  -

                                  Comment

                                    #18
                                    Re: Neoware Thin Client Trouble

                                    Thanks guys I appreciate that.

                                    Paul

                                    Comment

                                      #19
                                      Re: Neoware Thin Client Trouble

                                      I've got three of these with the same issue ..... do you ever solve it?

                                      Comment

                                        #20
                                        Re: Neoware Thin Client Trouble

                                        I have many of the Neoware EON 4000uw model. The power supply photo that Paul provided at the top of the thread looks the same so likely most of the Neoware models use similar supplies. Mine have the same symptoms as Paul described, ticking or completely dead.

                                        With the 3 ticking ones, a complete re-cap (15 caps) and they are OK. However, the remaining group required more research and bench testing.

                                        With the dead ones, I re-capped them (all 15 caps again) and then replaced ZD4. I measured it out at 17.6v, but replaced it with an 18v zener as they were easy to get. ZD4 shorts which doesn't kill the supply but you simply can't turn it on.

                                        ZD4 is part of the voltage generator for the 5Vsb (stand-by) supply line (purple wire). The system board uses this to switch the control line (green wire, labelled CTL) high or low to turn the supply on or off. The small transformer T2 provides the AC power for the rectified 5Vsb, along with ZD3 (likely a 5 or 5.1 zener) and filters C21 & C22. When off, ZD4 sits at 18 volts and waits to turn on the supply. When the power switch is pushed, the CLT line flips and pushes the voltage down across ZD4 to about 14.4 volts, enabling the main oscillator and turning on the supply.

                                        For a complete re-cap of the unit, the following chart is useful. All caps are radial, general use aluminum electrolytic and need to be small sized.

                                        C19 - 47uF 35v
                                        C27 - 10uF 50v (I sub in a 63v)
                                        C3 - 100uF 25v

                                        C21 - 470uF 10v
                                        C22 - 100uF 25v
                                        C14 - 100uF 25v
                                        C13 - 220uF 25v
                                        C12 - 470uF 10v
                                        C25 - 10uF 50v (once again, I used a 63v)
                                        C16 - 100uF 25v
                                        C15 - 220uF 25v
                                        C7, C8, C10, C11 - 1000uF 6.3v

                                        Comment

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