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Signal Tracer (Old school)

supper_slash

One of my projects for this year is to create a "new age" signal tracer like I used when i was a kid.

What I had was an old heathkit IT-12 pictured below.

image

 

The thing is i have no clue how this worked. I loved using it, and well just playing with it. It was sencitive efuff to hear audio runing through circuts without contacting the circuts, just getting the tip close to a trace.

 

So to start things off I created a audio amplifyer circut that I think is how this unit worked.

image

There are 2 things that I am compleetly lost about though.

 

  1. How to make, or what to use for the probe.
  2. How to make the visual circut.

1~I was thinking of taking a nail, and wraping copper wire around the nail to create a pickup coil, but i have no idea if this would work or if there is something better to try.

I am open to any ideas.

 

2~I was thinking of a 10 segment led bargraph desplay. But where would I need to conect the driver up to in the circut in the diagram? Would it be the the + side of C5?

I ordered some LM358N LM358 358 Low Power Dual Op-Amp IC's for this project that should be here on the 10th.

So I am planning on bread boarding this after that.

 

Also, I was thinking about starting to documenting some of my projects by video maby. So this might be one of the first ones I may try to document.

I have been feeling inspired by @Peter Oakes.

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  • Taking in your suggestions, here is revision 2 of the circuit.

    image

     

    @John Wiltrout I was thinking the highlighted cap (C1) would provide the higher impedance needed. Am I thinking wrong?

    I love the idea of the probe, that will be the way to go.  Thank you for the  schematic, I am afraid I am not fluent with the tubes, however. image

    I am focusing on solid state, for now, I would like to move into the vacuum tubes later, I love the vintage tube amplifiers.

     

    @shabaz  

     

    I pulled the transistors off of the circuit, and plan to see if that can, in fact, drive a speaker/headphones. I have a feeling I will need something to drive them, so I am thinking of adding some fets like you mentioned in place of the PNP/NPN's.

    I like the input you have on this, do you have any posts or schematics of you circuits posted? or that you can share? Maby we can work together.?  image

    Just a thought.

    By the way, the led bar is added to the circuit.image

  • in reply to supper_slash

    Hi Lupe,

    When one talks about input impedance one is referring to the impedance looking into the input of the circuit. If I look into the input of your circuit I see the resistance of VR1. Look at the tube schematic and you will see if we look into the input we see the impedance of C2 at the least and if the RF switch is on we have the impedance of C1 and C2 in series. At least at low frequencies the capacitors have much higher impedance than the VR1. Don't worry too much about tube technology. I strongly suspect that it isn't coming back. I have been waiting with my tube manual in hand for 50 years. Good luck on your project.

    John

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  • in reply to supper_slash

    Hi Lupe,

    When one talks about input impedance one is referring to the impedance looking into the input of the circuit. If I look into the input of your circuit I see the resistance of VR1. Look at the tube schematic and you will see if we look into the input we see the impedance of C2 at the least and if the RF switch is on we have the impedance of C1 and C2 in series. At least at low frequencies the capacitors have much higher impedance than the VR1. Don't worry too much about tube technology. I strongly suspect that it isn't coming back. I have been waiting with my tube manual in hand for 50 years. Good luck on your project.

    John

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