69708Re: [softrock40] Re: Bad chip?
- Nov 2, 2012Noise 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
----- Original Message -----
From: "wfahle" <billfahle@...>
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 firstname.lastname@example.org, "MICHAEL TALLENT" <mwtallent@...>
>> You really want a low noise op-amp for this application as it will
>> 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: <email@example.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 firstname.lastname@example.org, "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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