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Re: RXTX Ensemble - RX Mixer

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  • 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 1 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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