Germanium Diode

Discussion in 'General Electronics Chat' started by pandian, Oct 21, 2009.

  1. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    Hi,

    I need a clarification on how to identify a Germanium Diodes spec which doesn't have any markings on that except a green band.
    It is in RF tuning assembly's signal reception device.
    Seems to a rectifier for RF signal.
    Its a clear glass type material made with orange colour at both side lead insertion and a green colour band at on end.

    Thanks.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    At a guess, it will look a lot like a 1N34.
     
  3. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Could also be a voltage-variable capacitor diode use to tune the LC network. How do you know it is Germanium? Did you forward bias it and measure the forward drop? Look at your circuit again. If the diode is reversed biased there then it is almost certainly a VVC.
     
  4. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    It's been labelled as CR1, Ge on the PCB, that's why i guess its a Germanium.It's been connected in series with a ceramic capacitor C1 at anode and inductor L1 at cathode. RF been fed to the circuit in series through C1. Signal leads through L1, in series to circuit.Any suggestion?
     
  5. flat5

    Active Member

    Nov 13, 2008
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    Can you attach the circuit or that part of it?
    IOW, show us the schematic.
     
  6. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    here's the schematic
     
  7. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    The best way I know to test them is out of circuit, using a DMM in the diode mode. A germaninum diode will have about .25 volts forward drop as opposed to a silicon with .6.

    The schematic certainly looks like an R.F. detector. Germanium diodes are preferred in this application specifially BECAUSE of their lower forward drop.

    eric
     
  8. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    ok, thanks so far.but once I found out its a Ge diode, then how bout the specs? like Vmax and aplications.. etc.
     
  9. beenthere

    Retired Moderator

    Apr 20, 2004
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    See post #2.
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I wonder if it could be a 1N35 (orange green=35). Sort of a long shot,
     
  11. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    Hi beenther,Thanks.Is it a point contact diode, or similar? Hi Ron H ,1N35 is similar to 1N34 but 22.5mA rate, where the latter is 50mA rate. Correct me if I'm wrong. If that's the case, can use either depends on the application needs?
     
  12. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    "Rate" is not a property of diodes.:D
    I looked at the American Microsemi specs for 1N34 and 1N35, and they don't make a lot of sense.
    What is "output current"?
    Why does V(FM) Max = 1V at a few milliamps?
    These are rhetorical questions, at least for you, so don't try to answer them.:)
    I don't know the answer to your questions, but it wouldn't hurt to try 1N34, which should be readily available.
     
  13. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    Hi, I don't really get wat u mean, may be I'm wrong with my question.Anyway, i measure the forward drop V, 3.6mV on my DMM.I've attached the image of it.Thanks
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    At what current did you measure the 3.6mV drop?

    And is that 3.6mV just one way? (meaning, is the diode not shorted?)
     
  15. pandian

    Thread Starter Active Member

    Sep 27, 2009
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    I measure as suggested in previous post, taken out diode form circuit, using diode continuity test mode in DMM.
    and apologize for the error. It's not 3.6mV but 0.36V.
     
    Last edited: Oct 24, 2009
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