SyncOptics SMPS - no output voltage

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  • emilije
    Senior Member
    • Aug 2010
    • 60
    #1

    SyncOptics SMPS - no output voltage

    Hi to all,

    OK, i have one SMPS from SynOptics and it's not working. Ratings are 100-220V 47-63Hz, 0.6A-0.03A, output is +5V 2A, +12V 0.7A and -12V 0.1A. It is used as power supply of some network hub (i need that hub working - and yes, i know that switch can be found under 20$ ) Fault is - no output voltage.

    When AC plug is plugged, i can measure 310V DC on main filter capacitor on primary side and the same (DC) voltage on primary side of transformer. There is no AC voltage on primary side of transformer. From the other, secondary side, there is absolutely zero voltage (ac or dc) comming from transformer. From secondary side, nothing looks burned, nothing shorted (measured by dmm), every component looks good on testing with dmm. I tried without cable cause i first thought that cable is shorted, but nothing. Only small discolouration on PCB is under switching transistor (i guess it is switching transistor), which can bee seen on the picture from above (near the bottom right corner).
    Caps are Rubycon
    Any ideas where to continue?

    Thank you!
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    • b700029
      Banned
      • Sep 2010
      • 640
      #2
      Re: SyncOptics SMPS - no output voltage

      From the lack of an IC I'm guessing it's a 2-transistor self-oscillating circuit.

      Check the transistors, they may have failed open.

        Comment

        • emilije
          Senior Member
          • Aug 2010
          • 60
          #3
          Re: SyncOptics SMPS - no output voltage

          Hi, thnx for the tip. I found this FET with markings SSP6N60A as failed.
          I can't find it here in shops, can you recommend replacements?

            Comment

            • retiredcaps
              Badcaps Legend
              • Apr 2010
              • 9271
              #4
              Re: SyncOptics SMPS - no output voltage

              Originally posted by emilije
              Hi, thnx for the tip. I found this FET with markings SSP6N60A as failed.
              I can't find it here in shops, can you recommend replacements?
              Wow, a name from the past. If I remember correctly, Synoptics and Wellfleet merged to become Bay Networks. Then Nortel bought Bay. And Nortel imploded.

              findchips.com shows no stock, but ebay has it for $1 + whatever for shipping

              http://www.ebay.com/sch/i.html?_from...&_nkw=SSP6N60A
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                Comment

                • b700029
                  Banned
                  • Sep 2010
                  • 640
                  #5
                  Re: SyncOptics SMPS - no output voltage

                  http://pdf1.alldatasheet.com/datashe...G/SSP6N60.html

                  Any N-channel MOSFET with equal or better ratings will work. There are many manufacturers making 6N60s.

                  You could also try getting a sample of e.g. 8N80 from here:
                  http://www.fairchildsemi.com/pf/FQ/FQP8N80C.html
                  http://www.fairchildsemi.com/tree/po...crete-mosfets/
                  Last edited by b700029; 11-22-2011, 01:05 AM.

                    Comment

                    • emilije
                      Senior Member
                      • Aug 2010
                      • 60
                      #6
                      Re: SyncOptics SMPS - no output voltage

                      Thnx guys, i found the same FET but there is no improvement. Any further ideas?

                        Comment

                        • b700029
                          Banned
                          • Sep 2010
                          • 640
                          #7
                          Re: SyncOptics SMPS - no output voltage

                          Check for anything else in the circuit that's damaged.

                          I wouldn't just replace one damaged component without checking all the others, or it might end up dead again.

                            Comment

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