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JFET identification

Discussion in 'Electronic Repair' started by JW, Nov 26, 2011.

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  1. JW

    JW Guest

    Hi all,

    Looking for a datasheet or any info on a FET used in a Keithley 2000
    location Q105. The service manual lists it as:
    TRANS, N CHANNEL JFET, SNJ132199(SOT-23)

    It is marked with three digits "132". Can't seem to find any data at all
    on the device.

    Thanks.
     
  2. Jamie

    Jamie Guest

    Yeah, it's tough trying to match up a JET if the pin off voltage is a
    critical part of the circuit. Also on top of that, it could be used as a
    current source which makes it just as tricky.

    I recently repaired a analog PID board that another tech repaired in
    the past. They replaced the JFET switch that is in the output that
    effectively turns the PID loop on/off. The way it is set in there, the
    gate pinch off voltage must fall in the range of 1 to 5 volts(-) and the
    tech put a NTExxx replacement in. That was a bad call. The NTE
    replacement had a gate pinch off voltage of 5..10V-. This circuit only
    had -5 max to play with. Needless to say, it wouldn't switch properly
    50% of the time. so wee went shopping for the original replacement,
    TO-92 package. guess what, I couldn't find any but I did find one that
    had the Gate voltage that I needed and the Idss was even better than the
    original.. So we go those. They are like gold these days!

    One friendly warning, beware of using NTE parts in critical areas.
    They don't always work.

    Jamie
     
  3. JW

    JW Guest

    Thanks for that. I think I'll try giving Keithley a call, maybe I'll get
    lucky...
     
  4. JW

    JW Guest

    Or not. They'll sell me the $2 part, but with a $150 minimum. They claim
    this part is made to Keithley spec (!). They also offered the following
    info:

    "I also show that we purchased these (which were not made to KI spec)
    Interfet SJN132280
    Fairchild Semiconductor 5149B51374A
    Fairchild Semiconductor 5149_NB51374B"

    I was unable to find any datasheets or stock on any of them. *sigh*
     
  5. Jamie

    Jamie Guest

    More than likely a standard fet in fairchild list of JFETS with a custom
    number on it for them. This is done very often to force you to
    use their service centers or to force you to buy new from them. However,
    buying new would mean they have a good product! :)

    THe last company I can remember that made custom things for their
    products were people like Tektronics and I know there are a slew of
    others that do that for undisclosed customers.

    If you had a schematic with voltages and basic functions as to what
    it does, it would be easy to come up with a replacement.

    Jamie
     
  6. haha, what assholes.
     
  7. Archon

    Archon Guest

    Wild guess

    Interfet IF1320?

    JC
     
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