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Checking a BC548B NPN Transistor?

Discussion in 'Electronic Basics' started by nospam, Jun 9, 2007.

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  1. nospam

    nospam Guest

    Does anyone know how to check a BC548B transistor using a basic digital
    multimeter?

    I have been trying to use the resistance and continuity checker but whatever
    combination of red/black leads on any of the 3 pins does not appear to do
    anything. I am sure I used to have output on one combination but I do not
    even have this now. I have tried multiple transistors.

    I either have a bad batch, broken them all somehow (possible) or I am not
    testing correctly (likely).

    I am trying to following the instructions here
    http://www.kpsec.freeuk.com/multimtr.htm#transistor - as I do not know the
    pin arrangement I am also trying to find out which is B (and C/E if
    possible) as I have conflicting data of either type TO92A or TO92C.

    Please help.
     
  2. Phil Allison

    Phil Allison Guest

    "nospam"

    ** Has it got a "diode test " function you can select on the switch ?

    If not, it will not test diodes or transistors.

    Get a meter that includes a transistor " Hfe " or "beta" test function.



    ....... Phil
     
  3. nospam

    nospam Guest

    ** Has it got a "diode test " function you can select on the switch ?

    No
    I also have a analogue meter should that do it? It has about 4 sets of
    options with 7 options in each set on a twirly dial should I be choosing the
    ohms resistance option but what range - 2Kohm or 20Kohm or higher / lower?

    TIA
     
  4. Meat Plow

    Meat Plow Guest

    Need a meter that at least tests diodes.
     
  5. nospam

    nospam Guest

    It seems to be a feature packed analogue meter is there a specific icon I
    should be looking for on the meter for a diode test?

    I am confused as the information at
    http://www.kpsec.freeuk.com/multimtr.htm#transistor seems to imply you can
    test without a diode option - you only need resistance? For resistance I
    have 20MOhm, 2M, 200k, 20k, 2k and 200 options and a beep/continutity test
    on my analogue meter?

    TIA
     
  6. Meat Plow

    Meat Plow Guest

    --|<--
     
  7. nospam

    nospam Guest

  8. Meat Plow

    Meat Plow Guest

  9. nospam

    nospam Guest

    Give it a try.

    I think I have it - I have found pins 1-2 (red-black lead) and 2-3
    (black-red lead) conduct to 700mV so I presume that means pin 2 is the B.
    Is there a method of seeing which is E and which is C or is that an educated
    guess?
     
  10. Meat Plow

    Meat Plow Guest


    Go here and scroll down to types.

    http://en.wikipedia.org/wiki/Transistor

    The testing data you have combined with the wiki data should help make
    clearer how to determine what is the emitter and collector from your meter
    readings. Your red lead should be on the base for an NPN and will conduct
    with the emitter and not the collector much like a diode.

    Have fun.

    --
    #1 Offishul Ruiner of Usenet, March 2007
    #1 Usenet Asshole, March 2007
    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    #8 AUK Hate Machine Cog
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     
  11. Allen Bong

    Allen Bong Guest

    If you click on "For further information please see the transistors
    page" on the page you gave, you'll find a simple transisitor tester
    "2. Testing in a simple switching circuit".

    Just made the circuit and insert the transistor in the CBE position.
    As you already known the B, so dont worry about the C & E first.
    Press the test button, if the LED goes on, you have C on the LED side
    and E on 0V. If not reverse C & E and try again.

    If the LED doesn't lite either way, the transistor is either bad, non
    NPN or not a transistor.

    Allen
     

  12. Download the datasheet and see the configuration:
    <http://www.datasheetcatalog.com/datasheets_pdf/B/C/5/4/BC548B.shtml>
    gives you a choice of four manufacturer's datasheets.

    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  13. Meat Plow

    Meat Plow Guest


    Shhhhh I'm trying to teach the boy :p


    --
    #1 Offishul Ruiner of Usenet, March 2007
    #1 Usenet Asshole, March 2007
    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    #8 AUK Hate Machine Cog
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     

  14. At least give him the textbook. You can't learn to fish without a
    hook, and some BAIT. ;-)


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  15. Meat Plow

    Meat Plow Guest

    I did, he had some link to checking transistors, I sent him to wiki for
    pnp an npn bipolar diagrams, showed him where his diode checker setting
    was on his meter. :p



    --
    #1 Offishul Ruiner of Usenet, March 2007
    #1 Usenet Asshole, March 2007
    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    #8 AUK Hate Machine Cog
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     

  16. That is a start, but the boy needs to learn to read datasheets, and
    now is as good a time as any! ;-)

    Just think of the things I could've done, if the net was around in
    the early '60s? A tube databook was a month's spending money when I was
    in Junior High School. Now there is so much good, free information that
    you couldn't adsorb it all in a lifetime. :(


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  17. Meat Plow

    Meat Plow Guest

    My entrance was around 1972. Tubes still ruled then. Was taken under the
    wing of a genius with all things tube. They still fascinate me,
    transistors are so on and off :)

    --
    #1 Offishul Ruiner of Usenet, March 2007
    #1 Usenet Asshole, March 2007
    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    #8 AUK Hate Machine Cog
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     

  18. Some things just can't be done with tubes. The KU band
    communications system I built that's aboard the ISS, for instance. Even
    if you could build it and get it into space, you'd need a nuclear
    reactor to power it. It would take out a lot of square miles, when it's
    orbit decayed.


    --
    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
     
  19. Meat Plow

    Meat Plow Guest

    Have a friend who worked for Ma Bell. He scrapped out many tube powered
    microwave relay sites and invited me to come load up on what was being
    tossed. I got a couple pickup loads of copper waveguide, big copper
    grounding strips with lugs on them, a 6ghz transmitter, all sorts of odd
    ball tubes and some usable from Western Electric. Hell everything was
    Western Electric. I was like a kid in a free candy shop.

    --
    #1 Offishul Ruiner of Usenet, March 2007
    #1 Usenet Asshole, March 2007
    #1 Bartlo Pset, March 13-24 2007
    #10 Most hated Usenetizen of all time
    #8 AUK Hate Machine Cog
    Pierre Salinger Memorial Hook, Line & Sinker, June 2004
    COOSN-266-06-25794
     
  20. nospam

    nospam Guest

    Download the datasheet and see the configuration:
    Thanks to everyone who has replied. I am really struggling as you can see.
    I can't believe that all my new BC548B transistors are broken.

    Does this seem correct?

    C = 4.98V
    B = 1183mV

    With E emitting 615mV

    Does not appear to amplifying anything to me? What could I have done wrong?

    TIA
     
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