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

Re: OT3m with Nuvi 350

Expand Messages
  • Mads
    Actually I have an old oscilloscope collecting dust in the basement. It should be suitable for AF measurements. Please provide some (detailed) instructions on
    Message 1 of 19 , Feb 2, 2012
      Actually I have an old oscilloscope collecting dust in the basement. It should be suitable for AF measurements. Please provide some (detailed) instructions on where to measure to the e-mail address on my qrz.com profile.

      73! Mads, la1tpa

      --- In tracker2@yahoogroups.com, Scott Miller <scott@...> wrote:
      >
      > Any chance you've got an oscilloscope to check what the audio level is?
      > I can walk you through checking a few places if you'd like. The
      > trackers are all tested for RX before they leave, but it's always
      > possible a solder joint failed or something.
      >
      > Scott
    • Scott Miller
      I m going to post this here so it s in the group archive. This applies to PCB v1.1 (note that there s a stray v1.0 marking in the lower left of the board - I
      Message 2 of 19 , Feb 7, 2012
        I'm going to post this here so it's in the group archive. This applies
        to PCB v1.1 (note that there's a stray v1.0 marking in the lower left of
        the board - I only recently discovered that.)

        The RX section is in the upper left of the board, near the radio DB9
        connector. You should see the input signal at ferrite chip L4 (left of
        D5, not marked). C2 and/or C18 (depending on whether SJ2 is set) AC
        couple the signal to the op amp input. You should see the op amp input
        on the left side of R2. You'll see the output at R9, which connects by
        a fat trace to the ADC input on the microcontroller. The entire audio
        path stays on the top layer of the PCB, and it's pretty visible because
        the traces are wider than anything but the power traces.

        Some problems I've seen that prevent RX from working are bad solder
        joints on components in that section, an improper value for C11 (should
        be 22pF, can be removed without any real impact), and an improper value
        for either R8 or R11 (both should be 30k and the voltage at their center
        point should be 1/2 Vcc).

        Scott

        On 2/2/2012 10:29 AM, Mads wrote:
        > Actually I have an old oscilloscope collecting dust in the basement. It
        > should be suitable for AF measurements. Please provide some (detailed)
        > instructions on where to measure to the e-mail address on my qrz.com
        > profile.
        >
        > 73! Mads, la1tpa
        >
        > --- In tracker2@yahoogroups.com <mailto:tracker2%40yahoogroups.com>,
        > Scott Miller <scott@...> wrote:
        > >
        > > Any chance you've got an oscilloscope to check what the audio level is?
        > > I can walk you through checking a few places if you'd like. The
        > > trackers are all tested for RX before they leave, but it's always
        > > possible a solder joint failed or something.
        > >
        > > Scott
        >
        >
      Your message has been successfully submitted and would be delivered to recipients shortly.