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RXTX Ensemble - RX Mixer

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  • hollingw@geneseo.net
    I am building the Softrock RXTX Ensemble and I can not get the correct testing results while building stage 6 - RX Mixer (QDS). Test Measurements Testpoint
    Message 1 of 4 , Oct 26, 2012
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      I am building the Softrock RXTX Ensemble and I can not get the correct testing results while building stage 6 - RX Mixer (QDS).

       

      Test Measurements

      Testpoint

      Units

      Nominal Value

      Author's

      Yours

      Pin 8

      Vdc

      0

      0

      0

      Pins 1 and 15 (PTT OFF)

      mVdc

      0 - 50

      50

       0

      Pin 2 (from Divider)

      Vdc

      2.5

      2.47

      2.5

      Pin 14 (from Divider)

      Vdc

      2.5

      2.47

      2.5

      Pin 7 (to OpAmp)

      Vdc

      2.5

      2.48

      1mV

      Pin 9 (to OpAmp)

      Vdc

      2.5

      2.48

      1mV

      Pin 16 (Vdd)

      Vdc

      5

      4.95

      5

      Pins 1 and 15 (PTT ON)

      Vdc

      high (Vdc)

      4.95

      5

       

      The previous assembly steps tested correctly.  I notice a problem in the voltage test from the Ensemble RXTX 06_RX Mixer (QSD).  Pins 7 and 9 of IC10 (FST3253) did not show any voltage either with the PTT enabled or disabled.

       

       I did not test with Rocky but used CFGSR.  Checked IC10 for bridges or shorts, nothing found.  I replaced the FST3253 and had the exact same results.

        Any suggestions?

       

    • Orin
      ... Check the FST3253 pins 3,6,11,12 - these should be 2.5V. If not, suspect T5, R53 and R54. With PTT disabled, make sure pins 1 and 15 are close to 0V. If
      Message 2 of 4 , Oct 26, 2012
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        --- In softrock40@yahoogroups.com, hollingw@... wrote:
        >
        >
        > I am building the Softrock RXTX Ensemble and I can not get the correct
        > testing results while building stage 6 - RX Mixer (QDS).
        >
        >
        >
        > Test Measurements
        >
        >
        > Testpoint
        >
        > Units
        >
        > Nominal Value
        >
        > Author's
        >
        > Yours
        >
        > Pin 8
        >
        > Vdc
        >
        > 0
        >
        > 0
        >
        > 0
        >
        > Pins 1 and 15 (PTT OFF)
        >
        > mVdc
        >
        > 0 - 50
        >
        > 50
        >
        > 0
        >
        > Pin 2 (from Divider)
        >
        > Vdc
        >
        > 2.5
        >
        > 2.47
        >
        > 2.5
        >
        > Pin 14 (from Divider)
        >
        > Vdc
        >
        > 2.5
        >
        > 2.47
        >
        > 2.5
        >
        > Pin 7 (to OpAmp)
        >
        > Vdc
        >
        > 2.5
        >
        > 2.48
        >
        > 1mV
        >
        > Pin 9 (to OpAmp)
        >
        > Vdc
        >
        > 2.5
        >
        > 2.48
        >
        > 1mV
        >
        > Pin 16 (Vdd)
        >
        > Vdc
        >
        > 5
        >
        > 4.95
        >
        > 5
        >
        > Pins 1 and 15 (PTT ON)
        >
        > Vdc
        >
        > high (Vdc)
        >
        > 4.95
        >
        > 5
        >
        >
        >
        >
        > The previous assembly steps tested correctly. I notice a problem in the
        > voltage test from the Ensemble RXTX 06_RX Mixer (QSD). Pins 7 and 9 of
        > IC10 (FST3253) did not show any voltage either with the PTT enabled or
        > disabled.
        >
        >
        >
        > I did not test with Rocky but used CFGSR. Checked IC10 for bridges or
        > shorts, nothing found. I replaced the FST3253 and had the exact same
        > results.
        >
        > Any suggestions?


        Check the FST3253 pins 3,6,11,12 - these should be 2.5V. If not, suspect T5, R53 and R54. With PTT disabled, make sure pins 1 and 15 are close to 0V. If not, suspect Q9 and R63 (it is 10k isn't it?).

        Orin.
      • Alan
        ... Subject: [softrock40] RXTX Ensemble - RX Mixer ... voltage test from the Ensemble RXTX 06_RX Mixer (QSD). Pins 7 and 9 of IC10 (FST3253) did not show any
        Message 3 of 4 , Oct 26, 2012
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          ----- Original Message -----
          Subject: [softrock40] RXTX Ensemble - RX Mixer



          >The previous assembly steps tested correctly. I notice a problem in the
          voltage test from the Ensemble RXTX 06_RX Mixer (QSD). Pins 7 and 9 of
          IC10 (FST3253) did not show any voltage either with the PTT enabled or
          disabled.


          Assuming the other voltages on U10 are correct, you do not list all of them.

          Measure the resistance between ground and pins 7 & 9.
          If low check R55, 58 are mounted correctly. Check C41, 42.
          Check for solder splashes or possibly bad etching of the PCB leaving whiskers to ground on these lines.

          73 Alan G4ZFQ
        • hollingw@geneseo.net
          Thanks Orin I checked the resistance from pins 11 and 12 to ground on IC10 and was reading 12 ohms on both pins. Since there is a 1K (R63) to ground, I
          Message 4 of 4 , Oct 27, 2012
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            Thanks Orin

            I checked the resistance from pins 11 and 12 to ground on IC10 and was reading 12 ohms on both pins. Since there is a 1K (R63) to ground, I realized that was too low. Checking T5, I saw one of leads shorting to a pad under the toriod. I moved the lead and everything checked out correctly. Thanks again for everyone's help with my problem. Now I can resume construction again.

            Thanks Walt

            --- In softrock40@yahoogroups.com, "Orin" <orin.eman@...> wrote:
            >
            > --- In softrock40@yahoogroups.com, hollingw@ wrote:
            > >
            > >
            > > I am building the Softrock RXTX Ensemble and I can not get the correct
            > > testing results while building stage 6 - RX Mixer (QDS).
            > >
            > >
            > >
            > > Test Measurements
            > >
            > >
            > > Testpoint
            > >
            > > Units
            > >
            > > Nominal Value
            > >
            > > Author's
            > >
            > > Yours
            > >
            > > Pin 8
            > >
            > > Vdc
            > >
            > > 0
            > >
            > > 0
            > >
            > > 0
            > >
            > > Pins 1 and 15 (PTT OFF)
            > >
            > > mVdc
            > >
            > > 0 - 50
            > >
            > > 50
            > >
            > > 0
            > >
            > > Pin 2 (from Divider)
            > >
            > > Vdc
            > >
            > > 2.5
            > >
            > > 2.47
            > >
            > > 2.5
            > >
            > > Pin 14 (from Divider)
            > >
            > > Vdc
            > >
            > > 2.5
            > >
            > > 2.47
            > >
            > > 2.5
            > >
            > > Pin 7 (to OpAmp)
            > >
            > > Vdc
            > >
            > > 2.5
            > >
            > > 2.48
            > >
            > > 1mV
            > >
            > > Pin 9 (to OpAmp)
            > >
            > > Vdc
            > >
            > > 2.5
            > >
            > > 2.48
            > >
            > > 1mV
            > >
            > > Pin 16 (Vdd)
            > >
            > > Vdc
            > >
            > > 5
            > >
            > > 4.95
            > >
            > > 5
            > >
            > > Pins 1 and 15 (PTT ON)
            > >
            > > Vdc
            > >
            > > high (Vdc)
            > >
            > > 4.95
            > >
            > > 5
            > >
            > >
            > >
            > >
            > > The previous assembly steps tested correctly. I notice a problem in the
            > > voltage test from the Ensemble RXTX 06_RX Mixer (QSD). Pins 7 and 9 of
            > > IC10 (FST3253) did not show any voltage either with the PTT enabled or
            > > disabled.
            > >
            > >
            > >
            > > I did not test with Rocky but used CFGSR. Checked IC10 for bridges or
            > > shorts, nothing found. I replaced the FST3253 and had the exact same
            > > results.
            > >
            > > Any suggestions?
            >
            >
            > Check the FST3253 pins 3,6,11,12 - these should be 2.5V. If not, suspect T5, R53 and R54. With PTT disabled, make sure pins 1 and 15 are close to 0V. If not, suspect Q9 and R63 (it is 10k isn't it?).
            >
            > Orin.
            >
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