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Re: Identify this mystery diode

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  • lilacbarn
    Thanks for the quick response Donald. That is my next step should there be no prior knowledge in this group. I will in fact test it with a constant current
    Message 1 of 11 , Sep 30 7:05 PM
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      Thanks for the quick response Donald. That is my next step should there be no prior knowledge in this group.
      I will in fact test it with a constant current source (set at say 500uA to start) sourced from some higher voltage like 20V or so.
      I was hoping for a quick answer and have some real data from a datasheet about its other characteristics - if it was not a low volt zener. e.g. type of diode, recovery time, reverse leakage and capacitance.
      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.
      > --
      > *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: Sunday, September 30, 2012 8:58:14 PM
      > > 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/616438547/pic/789168770/view?picmode=&mode=tn&order=ordinal&start=1&count=20&dir=asc
      > >
      > >
      > >
      > > ------------------------------------
      > >
      > > Please trim excess when replyingYahoo! Groups Links
      > >
      > >
      > >
      >
    • 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 2 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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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