Test with a multimeter

Logic gate (74HC00)

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Now: VCC to GND: short circuit check

5 V 1 CircuVanta 6000 counts · auto range DCAUTO•)))HOLDFUSE− HOLD LIGHT OFFV⎓V~Ω•)))FmA⎓ mA400 mACOMVΩ Gate 1 inputs (1A, 1B) 1 1–2 Gate 1 output (1Y) 3 Gate 2 inputs (2A, 2B) 4 4–5 Gate 2 output (2Y) 6 GND 7 GND Gate 3 output (3Y) 8 Gate 3 inputs (3A, 3B) 9 9–10 Gate 4 output (4Y) 11 Gate 4 inputs (4A, 4B) 12 12–13 VCC 14 VCC
Pin 1: Gate 1 inputs (1A, 1B) (1–2) Pin 3: Gate 1 output (1Y) (3) Pin 4: Gate 2 inputs (2A, 2B) (4–5) Pin 6: Gate 2 output (2Y) (6) Pin 7: GND (GND) Pin 8: Gate 3 output (3Y) (8) Pin 9: Gate 3 inputs (3A, 3B) (9–10) Pin 11: Gate 4 output (4Y) (11) Pin 12: Gate 4 inputs (4A, 4B) (12–13) Pin 14: VCC (VCC)

Red probe Not connectedBlack probe Not connected

Hold the probe and drag it to the tip of a leg. Tapping works too: first pick the probe, then the leg.

Set the range to Ω (resistance).

Test setup: Setup: it powers with 5 V; the two inputs of gate 1 (pin 1) are tied to one switch, and the inputs of the other gates are at 0 V. Use the “Power on” and “Set inputs to 1” buttons.

Measure step by step

The 74HC00 contains four NAND gates: the output is 0 only when both inputs are 1. When unpowered there must be no short circuit between VCC and GND. In the setup, the inputs of gate 1 are tied to a single switch: with the inputs at 1 the output should read 0 V, with the inputs at 0 it should read close to the supply. The multimeter cannot measure the IC’s temperature, behaviour under load or speed: this test only shows that there is no short circuit and that the setup gives the expected voltages. A good result means “it could not be proven faulty”.

Isolate the IC from the circuit; CMOS inputs are damaged by static electricity. Do not leave an unused input floating.

  1. 1VCC to GND: short circuit check
  2. 2Power on: VCC voltage
  3. 3Inputs 0: output of gate 1
  4. 4Inputs 1: output of gate 1