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RE: [Electronics_101] Identify this mystery diode

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  • Nuno T.
    Sometimes, reading those colour marks with artificial light might be difficult and prone to mistakes. Take that diode out to a very sunny place and see if
    Message 1 of 11 , Oct 1, 2012
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      Sometimes, reading those colour marks with artificial light might be
      difficult and prone to mistakes. Take that diode out to a very sunny place
      and see if those colours are the same. Some inks used for those colour marks
      can be tricky. I know that from my own experience.

      Nuno T.

      > -----Original Message-----
      > From: Electronics_101@yahoogroups.com
      > [mailto:Electronics_101@yahoogroups.com] On Behalf Of lilacbarn
      > Sent: segunda-feira, 1 de Outubro de 2012 1:58
      > To: Electronics_101@yahoogroups.com
      > Subject: [Electronics_101] Identify this mystery diode
      >
      > I need help to identify this diode.
      > It tests like a diode on standard multimeter.
      > The colours appear to be (from Cathode):
      > wide band-Grey, violet, white, black.
      >
      > From diode ID band Table on the web this seems to be 1N8790,
      > but I cannot make sense of this number from datasheets
      > listings on the web so I assume I must have read it incorrectly.
      > Can anyone help?
      > The picture is posted in the Photos section, Lilacbarn.
      > Thanks to anyone who can help.
      > I have quite a few of these that I could use if I knew what they were.
      > Geoff.
      >
      > http://groups.yahoo.com/group/Electronics_101/photos/album/616
      438547/pic/789168770/view?picmode=&mode=tn&order=ordinal&start=1>
      &count=20&dir=asc
      >
      >
      >
      > ------------------------------------
      >
      > Please trim excess when replyingYahoo! Groups Links
      >
      >
      >
    • lilacbarn
      Thanks Nuno, I had thought of that and there was not much difference. The photo in the photo section is taken with a daylight fluorescent. Geoff.
      Message 2 of 11 , Oct 1, 2012
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        Thanks Nuno, I had thought of that and there was not much difference.
        The photo in the photo section is taken with a "daylight" fluorescent.
        Geoff.

        --- In Electronics_101@yahoogroups.com, "Nuno T." <nuno-t@...> wrote:
        >
        > Sometimes, reading those colour marks with artificial light might be
        > difficult and prone to mistakes. Take that diode out to a very sunny place
        > and see if those colours are the same. Some inks used for those colour marks
        > can be tricky. I know that from my own experience.
        >
        > Nuno T.
        >
        > > -----Original Message-----
        > > From: Electronics_101@yahoogroups.com
        > > [mailto:Electronics_101@yahoogroups.com] On Behalf Of lilacbarn
        > > Sent: segunda-feira, 1 de Outubro de 2012 1:58
        > > To: Electronics_101@yahoogroups.com
        > > Subject: [Electronics_101] Identify this mystery diode
        > >
        > > I need help to identify this diode.
        > > It tests like a diode on standard multimeter.
        > > The colours appear to be (from Cathode):
        > > wide band-Grey, violet, white, black.
        > >
        > > From diode ID band Table on the web this seems to be 1N8790,
        > > but I cannot make sense of this number from datasheets
        > > listings on the web so I assume I must have read it incorrectly.
        > > Can anyone help?
        > > The picture is posted in the Photos section, Lilacbarn.
        > > Thanks to anyone who can help.
        > > I have quite a few of these that I could use if I knew what they were.
        > > Geoff.
        > >
        > > http://groups.yahoo.com/group/Electronics_101/photos/album/616
        > 438547/pic/789168770/view?picmode=&mode=tn&order=ordinal&start=1>
        > &count=20&dir=asc
        > >
        > >
        > >
        > > ------------------------------------
        > >
        > > Please trim excess when replyingYahoo! Groups Links
        > >
        > >
        > >
        >
      • Andy
        ... Are you aware that even daylight fluorescent lamps do not approximate true daylight very well? Fluorescents tend to have big gaps in their spectra. All
        Message 3 of 11 , Oct 1, 2012
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          > The photo in the photo section is taken with a "daylight" fluorescent.

          Are you aware that even "daylight" fluorescent lamps do not
          approximate true daylight very well? Fluorescents tend to have big
          gaps in their spectra. All the "daylight" means is that the general
          color cast is more or less similar to daylight in terms of its
          yellow-to-blue balance. But it still has the holes in the spectrum.
          If the pigment falls into one of those holes, it won't look right.

          Morale: don't use any kind of fluorescent or "white" LED to illuminate
          something where the actual color response is meaningful.

          Andy
        • jongkung01@yahoo.com
          While this true more and more high end / professional photograph and videography is being done with daylight balance fluorescent light banks. These are light
          Message 4 of 11 , Oct 1, 2012
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            While this true more and more high end / professional photograph and videography is being done with daylight balance fluorescent light banks.

            These are light designed for photography but I believe some / many / most will work with digital camera. I would test it out with some sort color chart.

            Either way when in doubt go outside in daylight and shoot a picture under cloudy sky or under some sort of white canopy.


            Jong



            On Oct 1, 2012, at 4:03 AM, Andy <ai.egrps@...> wrote:

            > Fluorescents tend to have big
            > gaps in their spectra. All the "daylight" means is that the general
            > color cast is more or less similar to daylight in terms of its
            > yellow-to-blue balance. But it still has the holes in the spectrum.
          • lilacbarn
            I have now done the reverse voltage test and got all the way up to 230v (1 Meg limiting resistor) with no breakdown so it is not a low voltage (7.9V +/-)
            Message 5 of 11 , Oct 1, 2012
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              I have now done the reverse voltage test and got all the way up to 230v (1 Meg limiting resistor) with no breakdown so it is not a low voltage (7.9V +/-) zener!
              Back to the experience of the group!

              As others are pointing out- I may have got the colours wrong due to internal lighting, but as I can see the same colours in incandescent light which has a broad continuous spectrum but warmer tone, I think they are very nearly right. But I will check in daylight tomorrow and see.

              Geoff.

              --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...> wrote:
              >
              > I'm going to guess it's a zener diode. Try applying 10VDC in reverse to it (through a 10k resistor) and see if there's 7.9V(+/-) across it.
              >
              > Donald.
            • Donald H Locker
              That s no 7V9 zener :) I probably would have stopped at 20 or 30V. Donald. -- *Plain Text* email -- it s an accessibility issue () no proprietary attachments;
              Message 6 of 11 , Oct 1, 2012
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                That's no 7V9 zener :) I probably would have stopped at 20 or 30V.

                Donald.
                --
                *Plain Text* email -- it's an accessibility issue
                () no proprietary attachments; no html mail
                /\ ascii ribbon campaign - <www.asciiribbon.org>

                ----- Original Message -----
                > From: "lilacbarn" <lilacbarn@...>
                > To: "Electronics 101" <Electronics_101@yahoogroups.com>
                > Sent: Monday, October 1, 2012 9:37:07 PM
                > Subject: [Electronics_101] Re: Identify this mystery diode
                >
                > I have now done the reverse voltage test and got all the way up to
                > 230v (1 Meg limiting resistor) with no breakdown so it is not a low
                > voltage (7.9V +/-) zener!
                > Back to the experience of the group!
                >
                > As others are pointing out- I may have got the colours wrong due to
                > internal lighting, but as I can see the same colours in incandescent
                > light which has a broad continuous spectrum but warmer tone, I think
                > they are very nearly right. But I will check in daylight tomorrow and
                > see.
                >
                > Geoff.
                >
                > --- In Electronics_101@yahoogroups.com, Donald H Locker <dhlocker@...>
                > wrote:
                > >
                > > I'm going to guess it's a zener diode. Try applying 10VDC in reverse
                > > to it (through a 10k resistor) and see if there's 7.9V(+/-) across
                > > it.
                > >
                > > Donald.
                >
                >
                >
              • Andy
                I admit knowing nothing about color-codes to mark diodes. I never encountered them before. But I m wondering if one is supposed to skip the cathode band and
                Message 7 of 11 , Oct 1, 2012
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                  I admit knowing nothing about color-codes to mark diodes. I never
                  encountered them before.

                  But I'm wondering if one is supposed to skip the cathode band and
                  start with the next one?

                  Also wondering if that third band is white, or grey (though a lighter
                  grey than the one marking the cathode end).

                  If so, then you might get a 1N790 or 1N780 out of the remaining color bands.

                  (My ignorance is showing!)

                  Andy
                • lilacbarn
                  Good idea to maybe skip the cathode band, but one of the web band pages thinks it should be included. I have added another photo as suggested taken in daylight
                  Message 8 of 11 , Oct 2, 2012
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                    Good idea to maybe skip the cathode band, but one of the web band pages thinks it should be included.
                    I have added another photo as suggested taken in daylight and the colours do seem a little different.

                    http://groups.yahoo.com/group/Electronics_101/photos/album/616438547/pic/1850130508/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc

                    Photo taken in bright sun (daylight) with camera set to "bright sun" colour balance. Bands look like Grey(cathode), violet/blue, white/silver, black (only just visible on the dark body colour).

                    If they are 1N790 then it would be a fast recovery signal diode which might make sense.

                    Has anyone else any more knowledge or help?
                    Thanks Geoff.


                    --- In Electronics_101@yahoogroups.com, Andy <ai.egrps@...> wrote:
                    >
                    > I admit knowing nothing about color-codes to mark diodes. I never
                    > encountered them before.
                    >
                    > But I'm wondering if one is supposed to skip the cathode band and
                    > start with the next one?
                    >
                    > Also wondering if that third band is white, or grey (though a lighter
                    > grey than the one marking the cathode end).
                    >
                    > If so, then you might get a 1N790 or 1N780 out of the remaining color bands.
                    >
                    > (My ignorance is showing!)
                    >
                    > Andy
                    >
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