DIY scope probe

Discussion in 'General Electronics Chat' started by Art, May 27, 2014.

  1. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Hi Guys,
    I fixed an old scope that belongs to my radio club last night but it has no probes.
    I was hoping for lower frequency stuff such as checking ripple in power supplies, etc.
    it might be acceptable to homebrew one using an alligator clip for negative,
    and a spare DMM probe that I have in the junk box for positive.

    I'm wondering if anyone can tell me what's in the trimmer circuit besides the
    capacitor used to trim the probe lead?
    Cheers, Art.
     
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    Sure you can "make do" with a piece of coax, an aligator clip and a pointy thing...

    Or you could just buy a set of new 'scope probes from ebay for $12 with multiple attachments, trimmer and 10:1 switch all built in.

    Your choice. :)
     
  3. crutschow

    Expert

    Mar 14, 2008
    12,977
    3,220
    The trimmer cap is used for a 10:1 probe. It's not needed for a 1:1 (direct) probe.
     
  4. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Ah, ok.. the commercial 1x probes are usually also 10x probes here (with a switch), so they all have the trimmer.

    Yeah, RB, err... I fixed the thing, someone else can buy the leads :D

    Last club meeting someone brings a linear power supply they made from scratch to
    use the scope to test it's capacitors are big enough to smooth the DC supply.
    Scope has no power cable.

    Last night I bring the IEC power cable so if anyone wants to use it it's there.
    Scope has no test leads.. it's a freaken display piece :rolleyes:
    I power it up and it starts to stink the room so I turn it off, take it home,
    change electrolytics around the PSU, and it goes fine and no smoke,
    so I'm guessing the transformer was about to burn.

    [​IMG]
     
  5. ScottWang

    Moderator

    Aug 23, 2012
    4,850
    767
    Using BNC male connector and cable for scope, and another side using two aligator clips.
     
  6. Art

    Thread Starter Distinguished Member

    Sep 10, 2007
    785
    61
    Nice Idea, I did consider alligator clips for CH2, and probe + alligator clip for CH1.
    Just depends how many half alligator clip leads I have..
    Alligator clips are a bit like gold at my place :D

    Someone had better be using this thing!
     
  7. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,344
  8. ScottWang

    Moderator

    Aug 23, 2012
    4,850
    767
    You also can be using small SMD IC Single Hook Clip.

     
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