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69705Re: Bad chip?

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  • wfahle
    Nov 2, 2012
      Ok, I've recovered from the brain fart, and am back on track now. This OP-Amp (dual) is in the transmitter, as U6. Do you think noise will cause a problem? I think I will try it anyway this weekend, because I am installing it dead-bug style with individual wires to each lead, so it will be easily replaced. This will allow me to finish the transmitter and see what I get signal-report wise.

      --- In softrock40@yahoogroups.com, "MICHAEL TALLENT" <mwtallent@...> wrote:
      > You really want a low noise op-amp for this application as it will determine
      > the noise floor of your receiver. The data sheet you linked looks like
      > nothing special, so you will not get the performance that these receivers
      > are capable of.
      > Mike T W6MXV
      > ----- Original Message -----
      > From: "wfahle" <billfahle@...>
      > To: <softrock40@yahoogroups.com>
      > Sent: Wednesday, October 31, 2012 12:31 PM
      > Subject: [softrock40] Re: Bad chip?
      > > Well NOW it's the chip for sure. In an attempt to remove the IC to check
      > > voltages and such, the green covering began to burn through exposing the
      > > copper traces beneath. So I got out the clippers and clipped it loose from
      > > the board, so that I could remove each lead individually. This worked, but
      > > it tore up some of the pads in the process. I intend to replace it with
      > > this chip because it is available locally (and I don't think going SMT
      > > again is going to make life any easier):
      > > http://www.nteinc.com/specs/700to799/pdf/nte778a.pdf
      > >
      > > --- In softrock40@yahoogroups.com, "wfahle" <billfahle@> wrote:
      > >>
      > >> Ok, I pulled R16, and it still reads 5v at pin 1. R16 measures out at 10k
      > >> as it should, but with it pulled there is very little voltage at pin 2.
      > >> The current, since I can now measure it, across R16 is .24mA. The votage
      > >> at pin 7 doesn't change either; it's still almost zero. The others
      > >> besides 2 are unchanged. Pin 2 goes almost to zero vs. the 2.5 it had
      > >> been reading. I guess R16 becomes part of a voltage divider under the
      > >> circumstances; I don't understand circuits this complex. So I will try to
      > >> unseat U6 and see if there is a solder bridge under it from 1 to 8 or
      > >> something (they are across from each other).
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