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Thread: How do connect a NTE7172 8-Lead DIP with an SCR for a crowbar circuit?

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  1. #1

    Default How do connect a NTE7172 8-Lead DIP with an SCR for a crowbar circuit?

    I want to make a crowbar circuit to help reduce overvoltage problems on my TS-940. I came across the NTE component "7172 8-Lead DIP", but I can't find clerification on what pins to connect to what part of the circuit. Now I know this is bound to bring some criticism, but I want to use the NTE circuit as opposed to what has been common place. I can't get NTE to cough up any sample diagrams.

    My guess is the Vcc, pin 1, will go to the 28.5 vegulator 'out' and the Vee to ground (this is a positive voltage supply). I believe the Drive Output , pin 8, should be connected to the trip leg of the SCR and the Sense 1 leg, pin 2, to pin 1 of the IC (short pin 2 to pin 1) with the idea that if the regulator out changes more than 2.6 volts, pin 8 will send the drive signal to the SCR and pop the in-line fuse. I thiink there is an internal zenier creating a reference voltage for which the Sense inputs use, or maybe that was a bad dream.
    Anyone willing to put their expertise on the line?
    W6LE

  2. #2
    Join Date
    Nov 2008
    Location
    Laguna Niguel, Ca.
    Posts
    5,655

    Default

    Quote Originally Posted by W6LE View Post
    I want to make a crowbar circuit to help reduce overvoltage problems on my TS-940. I came across the NTE component "7172 8-Lead DIP", but I can't find clerification on what pins to connect to what part of the circuit. Now I know this is bound to bring some criticism, but I want to use the NTE circuit as opposed to what has been common place. I can't get NTE to cough up any sample diagrams.

    My guess is the Vcc, pin 1, will go to the 28.5 vegulator 'out' and the Vee to ground (this is a positive voltage supply). I believe the Drive Output , pin 8, should be connected to the trip leg of the SCR and the Sense 1 leg, pin 2, to pin 1 of the IC (short pin 2 to pin 1) with the idea that if the regulator out changes more than 2.6 volts, pin 8 will send the drive signal to the SCR and pop the in-line fuse. I thiink there is an internal zenier creating a reference voltage for which the Sense inputs use, or maybe that was a bad dream.
    Anyone willing to put their expertise on the line?
    W6LE
    Try this link.

    http://www.onsemi.com/pub_link/Collateral/MC3423-D.PDF
    Pull my finger. Part II. On second thought, pull your own finger.

  3. #3

    Default

    David ... Thank you for the reference. Fits just right.

    Sincerely,
    Jim W.

  4. #4
    Join Date
    Nov 2008
    Location
    Laguna Niguel, Ca.
    Posts
    5,655

    Default

    Quote Originally Posted by W6LE View Post
    David ... Thank you for the reference. Fits just right.

    Sincerely,
    Jim W.
    You are welcome.
    Pull my finger. Part II. On second thought, pull your own finger.

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