69649Re: Bad chip?
- Nov 1 5:51 AMGood to know. In other news, the unit is no longer kerchunking when connected to USB. I mentioned elsewhere that I was able to receive a garbled SSB signal and an intelligible CW signal with a hallway dipole after completing the receiver stage of the build, but now it no longer responds to the computer at all. So this one is bricked; I must have discharged static into it at some point, explaining the other chip failure too.
I am off to order another kit and a wrist strap/static mat. I hadn't been taking any particular precautions with regard to static, and having successfully built through the receiver stage I got complacent. I was building in a carpeted room with a non-grounded solder station (http://www.frys.com/product/4825200?source=googleps&gclid=CLqxhPPlrbMCFZGPPAodRz4ASQ) and touching the leads with reckless abandon, so lesson learned there. I think it was the fuzzy slippers and the tesla coil that finally did me in.
By the way, I don't consider this build a failure because of all I learned along the way. The next build will go much faster and be cleaner and better. I was never happy with the way I left some of the power supply capacitors floating 1/8" off the board now that I know how to avoid it, so that would have bugged me through the life of the radio. I also put a resistor in upside down (affecting only readability of the part), which admittedly is a small thing compared with a dead USB controller and a noisy radio.
--- In email@example.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: <firstname.lastname@example.org>
> 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 email@example.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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