Heathkit Cointrack GD-1190

Schematic diagram of the Heathkit Cointrack GD-1190 metal detector
Fig. 1: Heathkit Cointrack GD-1190 metal detector schematic diagram

Parts list


  • IC1: LF211 (FET input voltage comparator IC)
  • IC2: LM2902 (Quad Operational Amplifier)
  • IC3: CA3130 (BiMOS Operational Amplifier)
  • IC4: CD4011 (Quad 2-Input NAND)
  • IC5: CD4024 (7-Stage Ripple Carry Binary Counter)


  • Q1: 2N4117 (N-channel JFET transistor)
  • Q2, Q4: MPSA20 (NPN 40V 100mA TO-92)
  • Q3, Q6: MPSA55 (PNP 60V 500mA TO-92)
  • Q5: MPSA13 (NPN Darlington Transistor)


  • D1: MV2110 (30V Vrrm, 39pf Varactor Diode)
  • D2, D3: 1N5230B (4.7V, 0.5W Zener Diode)
  • D4: 1N4149 or 1N4148 (switching diode)


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.
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