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71752Re: [softrock40] Re: U10 / U11 problems

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  • Michael Walker
    Jan 17, 2013
      Fixed it.

      On a wim, I pulled off U10 (with the chip quik it is a 20 second job).

      I cleaned the board and resoldered it back in place.

      There must have been a solder splash or something that I could not see.

      Anyway, that stage is done.  

      Of course, I had just ordered some spare parts from Digi Key.  Isn't that way it always happens!

      Oh, the ripple is gone as well.

      Mike va3mw

      p.s.  Thanks for all the support from everyone

      On Thu, Jan 17, 2013 at 10:20 PM, warrenallgyer <allgyer@...> wrote:
       

      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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