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Intermittent LO output on Ensemble TX/RX

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  • h56thy4
    I would be grateful for some advice please. I am building the Ensemble TX/RX. This is my first experience of SDR, and of SMT, although I have built many
    Message 1 of 3 , Dec 1, 2010
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      I would be grateful for some advice please. I am building the Ensemble TX/RX. This is my first experience of SDR, and of SMT, although I have built many (discreet component)homebrew projects in the past, and consider myself to be fairly proficient at construction.
      The 12v and USB powers supplies went OK. I carefully measured the value of each item before installing, and also checked that it connected to where it was supposed to go, and not to earth (unless intended). The software installation was also fairly trouble free (using Vista). The LO would not oscillate, or give the correct indications on the CFGSR tabs at first, but this was resolved after I re-flowed the Si570 solder joints.
      The problem that I now have is that the circuit oscillates (checked on RX) and appears to perform correctly on start-up, but fades away after 20 to 30 seconds. The indications on the CFGSR tabs remain normal however.
      Question: do I still have a cold-soldered joint somewhere, or do I have one of the faulty SI570's that were reported by Tony?
      Also, is there anywhere that shows what the voltages should be around the LO cct when it is operating correctly?
      Finally, why is pin 1 of the Si570 taken to ground via a capacitor, when the manufacturer's documentation says it should be unconnected?

      Regards Colin Richardson G4OCZ
    • Alan
      ... From: h56thy4 Subject: [softrock40] Intermittent LO output on Ensemble TX/RX ... If it has + and - voltages it should oscillate. Pin 2 has an internal
      Message 2 of 3 , Dec 1, 2010
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        ----- Original Message -----
        From: "h56thy4"
        Subject: [softrock40] Intermittent LO output on Ensemble TX/RX



        > The problem that I now have is that the circuit oscillates (checked on RX)
        > and appears to perform correctly on start-up, but fades away after 20 to
        > 30 seconds. The indications on the CFGSR tabs remain normal however.
        > Question: do I still have a cold-soldered joint somewhere, or do I have
        > one of the faulty SI570's that were reported by Tony?
        > Also, is there anywhere that shows what the voltages should be around the
        > LO cct when it is operating correctly?

        If it has + and - voltages it should oscillate.
        Pin 2 has an internal pull-up, if there is a leakage to ground it could stop
        the device. Pin 4, I think, will be around 1V5, Pin 5 NC voltage CMOS, I'm
        not sure.
        If CFGSR shows everything correctly then it should work.
        I do not think this sounds like Tony's faulty ones, look back to see his
        description, something about some sort of spurious operation.
        We have always thought them to be reliable devices but there have been a few
        faulty.

        > Finally, why is pin 1 of the Si570 taken to ground via a capacitor, when
        > the manufacturer's documentation says it should be unconnected?

        Pass. This pin is used with the Si571.

        73 Alan G4ZFQ
      • h56thy4
        Thanks for your reply Alan. I re-flowed the Si570 again, and that fixed the problem - lousy soldering! My first experience of this type of construction, and I
        Message 3 of 3 , Dec 4, 2010
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          Thanks for your reply Alan. I re-flowed the Si570 again, and that fixed the problem - lousy soldering! My first experience of this type of construction, and I was nervous about damaging the components with excessive heat. It seems that they are amazingly robust (or perhaps I'm just lucky)Now making good progress

          73 Colin G4OCZ

          --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
          >
          >
          > ----- Original Message -----
          > From: "h56thy4"
          > Subject: [softrock40] Intermittent LO output on Ensemble TX/RX
          >
          >
          >
          > > The problem that I now have is that the circuit oscillates (checked on RX)
          > > and appears to perform correctly on start-up, but fades away after 20 to
          > > 30 seconds. The indications on the CFGSR tabs remain normal however.
          > > Question: do I still have a cold-soldered joint somewhere, or do I have
          > > one of the faulty SI570's that were reported by Tony?
          > > Also, is there anywhere that shows what the voltages should be around the
          > > LO cct when it is operating correctly?
          >
          > If it has + and - voltages it should oscillate.
          > Pin 2 has an internal pull-up, if there is a leakage to ground it could stop
          > the device. Pin 4, I think, will be around 1V5, Pin 5 NC voltage CMOS, I'm
          > not sure.
          > If CFGSR shows everything correctly then it should work.
          > I do not think this sounds like Tony's faulty ones, look back to see his
          > description, something about some sort of spurious operation.
          > We have always thought them to be reliable devices but there have been a few
          > faulty.
          >
          > > Finally, why is pin 1 of the Si570 taken to ground via a capacitor, when
          > > the manufacturer's documentation says it should be unconnected?
          >
          > Pass. This pin is used with the Si571.
          >
          > 73 Alan G4ZFQ
          >
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