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Heathkit Groundtrack GR-1290 VLF Schematics

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  • Heathkit Groundtrack GR-1290 VLF Schematics

    Heathkit Groundtrack GR-1290 VLF metal detector


    Notes

    All resistors are 1/4 watt, 5% tolerance and all capacitors are in microfarads (uF) unless marked otherwise.
    Voltages were taken with a 9 Volt supply and a setting with no sound coming from the speaker. The controls were set as follows:
    • Volume -- fully counterclockwise
    • Pushbutton tune -- center of rotation
    • Discriminate -- center of rotation
    • Audio Tune -- center of rotation

    The original coil that came with the Heathkit project was preassembled at the factory. It had a diameter of around 15cm (6 inch). A larger (30cm, 12inch) coil can be made using the following data:
    L1 = 300mm diameter, 90 turns, .4mm wire
    L2 = 140mm diameter, 90 turns, .4mm wire
    L3 = 130mm diameter, 550 turns, .1mm wire

    Parts list

    ICs:

    • U1: CA3130S (BiMOS Operational Amplifier)
    • U2, U3: LM308 (Precision operational amplifiers)
    • U4: LM2901 (Quad Single Supply Comparator IC)

    Transistors:

    • Q1, Q4, Q9, Q10, Q11, Q12: MPSA20 (NPN 40V 100mA)
    • Q2, Q7, Q8, Q13: MPSA55 (PNP 60V 500mA)
    • Q3, Q5: 2N4117 (N-channel JFET transistors)
    • Q6: MPSA13 (NPN Darlington transistor)

    Diodes:

    • D1, D3, D4: 1N4149 or 1N4148 (switching diodes)
    • D2: 1N5230B (4.7V, 0.5W Zener Diode)
    Attached Files

  • #2
    This was my first "serious" detector which I built. This was 28 years backwards. This omega coil is drawn my hand. Oh, the nostalgy embraces.
    Mrand

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    • #3
      How does this compare to the other detectors of this time - Garrett and Whites? I kind of looked down on it being a "kit."

      Comment


      • #4
        Hello!!, check this out, take him out of a Polish site for some time and today is no longer.
        Attached Files

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        • #5
          The capacitors C22, C25 and C26 are electrolytic in the PCB are as ceramics for space
          if someone can check I would appreciate
          [IMG]file:///C:/DOCUME%7E1/ADMINI%7E1/Temp/moz-screenshot.png[/IMG]
          Attached Files

          Comment


          • #6
            Adding file

            ..
            Attached Files

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