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Re: Bad chip? Not that one, in any case.

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  • wfahle
    I am giving continuity checks now. I was reading 5v on pin 1, which was the original problem that made me suspect the chip was bad. In fact it looks like R15
    Message 1 of 28 , Nov 3, 2012
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      I am giving continuity checks now. I was reading 5v on pin 1, which was the original problem that made me suspect the chip was bad. In fact it looks like R15 is shorted to ground between it and C6+. That is not indicated in the schematic, so I'm now pulling R15.

      --- In softrock40@yahoogroups.com, "Alan" <alan4alan@...> wrote:
      >
      >
      > ----- Original Message -----
      > Subject: [softrock40] Re: Bad chip? Not that one, in any case.
      >
      >
      > > It indicates 5v on pin 1, Just like the other one in that respect. With power off, I'm currently reading 20.9 Kohms between pin 1
      > > and pin 8, which when reviewing the schematic doesn't seem right. In fact the other dual op-amp which seems wired similarly is an
      > > open circuit between those pins, giving me more confidence that this is the problem. I'm reading 11Kohms between 8 and 2 on U6,
      > > which is probably where the 20.9 is coming from adding R16 (which spans 1 and 2). Any ideas anyone? Clearly there is a short
      > > somewhere, and not a bad chip after all.
      > >
      >
      >
      > I do not remember you giving the voltages you see on this chip.
      >
      > 73 Alan G4ZFQ
      >
    • wfahle
      Found the problem. See other thread.
      Message 2 of 28 , Nov 3, 2012
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        Found the problem. See other thread.

        --- In softrock40@yahoogroups.com, "wfahle" <billfahle@...> wrote:
        >
        > I am giving continuity checks now. I was reading 5v on pin 1, which was the original problem that made me suspect the chip was bad. In fact it looks like R15 is shorted to ground between it and C6+. That is not indicated in the schematic, so I'm now pulling R15.
        >
        > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
        > >
        > >
        > > ----- Original Message -----
        > > Subject: [softrock40] Re: Bad chip? Not that one, in any case.
        > >
        > >
        > > > It indicates 5v on pin 1, Just like the other one in that respect. With power off, I'm currently reading 20.9 Kohms between pin 1
        > > > and pin 8, which when reviewing the schematic doesn't seem right. In fact the other dual op-amp which seems wired similarly is an
        > > > open circuit between those pins, giving me more confidence that this is the problem. I'm reading 11Kohms between 8 and 2 on U6,
        > > > which is probably where the 20.9 is coming from adding R16 (which spans 1 and 2). Any ideas anyone? Clearly there is a short
        > > > somewhere, and not a bad chip after all.
        > > >
        > >
        > >
        > > I do not remember you giving the voltages you see on this chip.
        > >
        > > 73 Alan G4ZFQ
        > >
        >
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