Loading ...
Sorry, an error occurred while loading the content.

69649Re: Bad chip?

Expand Messages
  • wfahle
    Nov 1 5:51 AM
    • 0 Attachment
      Good 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.

      Bill K5WL

      --- 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).
    • Show all 28 messages in this topic