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69708Re: [softrock40] Re: Bad chip?

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  • MICHAEL TALLENT
    Nov 2, 2012
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      Noise probably will not matter for the transmitting side, the output level
      may not be as good as amps designed for low voltage operation, but try it
      and see.

      Mike T

      ----- Original Message -----
      From: "wfahle" <billfahle@...>
      To: <softrock40@yahoogroups.com>
      Sent: Friday, November 02, 2012 12:46 PM
      Subject: [softrock40] Re: Bad chip?


      > 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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