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71751Re: U10 / U11 problems

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  • warrenallgyer
    Jan 17, 2013
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      Mike

      I am on the road at the moment so I cannot look at my 5V line. My instinct is the ripple should not be there and should be shunted off by the bypass caps. On the other hand 0.4 V is not enough to clock any of the CMOS and I doubt it is the source of any problem.

      Glad you are up to speed on the probes.... I mentioned it as a reminder to myself as well. I have to tell myself "calibrate first!" when making critical measurements......

      Good luck

      Warren Allgyer - W8TOD

      --- In softrock40@yahoogroups.com, Michael Walker wrote:
      >
      > Thanks Warren
      >
      > Yep, I had adjusted the probe compensation. It is good to mention for
      > those that have not had to do that before.
      >
      > Want to grab some shots and post them so that others can reference them as
      > well as both good and or bad.
      >
      > I am also concerned with the 0.4vp-p 7mhz ripple on the 5vDC line.
      >
      > Mike
      >
      > On Thu, Jan 17, 2013 at 1:29 PM, warrenallgyer wrote:
      >
      > > **
      > >
      > >
      > > Mike
      > >
      > > The square waves will likely not be perfectly square. I normally see
      > > nearly a volt of "ringing" on the corners. Once the ringing has settled the
      > > remainder should be fairly flat. This of course assumes you have properly
      > > adjusted the compensation on the probes. Easy way to do this is to probe
      > > the scope calibrator and adjust for perfect flatness on the calibration
      > > square wave.
      > >
      > > Warren Allgyer - W8TOD
      > >
      > >
      > > --- In softrock40@yahoogroups.com, Michael Walker wrote:
      > > >
      > > > Thanks Alan
      > > >
      > > > A bad U10 is what I was thinking. I've also scoped the outputs from T5
      > > and
      > > > they are similar, but there is a difference between the 2 of them. I
      > > would
      > > > expect to see very similar waveforms.
      > > >
      > > > The other interesting thing is that I am seeing a .4 V P-P 7Mhz ripple on
      > > > the 5VDC line.
      > > >
      > > > My scope is a 100Mhz Tektronic dual trace scope.
      > > >
      > > > Should the waveforms on the dividers be perfectly square?
      > > >
      > > > If I get a chance later today, I will post some pics of the wave forms.
      > > >
      > > > Mike va3mw
      > > >
      > > >
      > > > On Thu, Jan 17, 2013 at 2:39 AM, Alan wrote:
      > > >
      > > > >
      > > > > ----- Original Message -----
      > > > > Subject: Re: [softrock40] U10 / U11 problems
      > > > >
      > > > >
      > > > > >On U10
      > > > >
      > > > > Pin 2 - 2.44 - Out - Pin 7 - 1.54
      > > > > Pin 14 - 2.30 Out - Pin 9 - 3.20
      > > > >
      > > > > Any thought why the imbalance that large? A problem with my winding of
      > > T5?
      > > > >
      > > > > Mike,
      > > > >
      > > > > Variations here is reckoned to be due to imbalance of stray capacity
      > > > > inside the chip.
      > > > > It is normal and will change with frequency.
      > > > > I'm not sure but yours seem high.
      > > > > TX mode switches off U10. I do not think T5 could cause it, there is
      > > not
      > > > > even any RF there.
      > > > >
      > > > > I wonder if C41, 42 can do this? Or a bad U10?
      > > > >
      > > > > 73 Alan G4ZFQ
      > > > >
      > > > >
      > > > > ------------------------------------
      > > > >
      > > > > Yahoo! Groups Links
      > > > >
      > > > >
      > > > >
      > > > >
      > > >
      > >
      > >
      > >
      >
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