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Transistor identification help (HP3457A)

Discussion in 'Electronic Repair' started by JW, May 18, 2007.

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  1. JW

    JW Guest

    I have a TO-92 Motorola transistor that I've been unable to identify. It
    markings are:
    | 4-|
    | 094|
    The m in the above pic is the Motorola logo.

    It's out of a HP 3457A DMM. Unfortunately, none of the service manuals
    that I've downloaded has the schematic or parts list of this particular
    revision of the circuit board. It located on the analog portion of the
    meter and is part of the optically coupled serial interface to the digital

    Thanks for any help!
  2. Eeyore

    Eeyore Guest

    How do you know it's a transistor ?

  3. JW

    JW Guest

    Assuming. I, of course, could be wrong...
    The device is shorted, so I can't test it to be sure. Of course it's the
    only one in the whole meter, otherwise I could have extracted another for
  4. They appear to be HP numbers.
    The 4- is the end of 1854-xxxx. Don't know about the rest. I have a pdf file of
    cross references if you want it? email me direct.

  5. carneyke

    carneyke Guest

    On the circuit board is there a reference designator for the part
    (Q123 for example) ?
  6. Ken

    Ken Guest

    I have a cross reference that says (if the above is true) that it is
    1854-0094 = MPS3646 Don't know if this is even similar, but just
    thought I would throw it out there.
  7. JW

    JW Guest

    Bingo! That was it. Meter is up and running again. Thanks everybody for
    all your help, and thank you Colin for those cross refs - they will prove
    to be quite valuable, I'm sure!
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