Test with a multimeter

Voltage regulator (7805)

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Now: IN to GND: short circuit check

9 V CircuVanta 6000 counts · auto range DCAUTO•)))HOLDFUSE− HOLD LIGHT OFFV⎓V~Ω•)))FmA⎓ mA400 mACOMVΩ IN (input) 1 IN GND 2 GND OUT (output) 3 OUT
Pin 1: IN (input) (IN) Pin 2: GND (GND) Pin 3: OUT (output) (OUT)

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 applies 9 V to the input and the output is unloaded. Pressing “Power on” applies the voltage; cut the supply before Ω measurements.

Measure step by step

Remove the regulator from the circuit. When unpowered, there must be no short circuit between input (IN) and ground (GND) or between input and output (OUT). To check the output, a test setup is used: 9 V is applied to the input and the output is measured on the V⎓ range. 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 and measure it unpowered. Do not use the Ω range on a pin that has voltage on it. The metal tab is GND and it gets hot while working.

  1. 1IN to GND: short circuit check
  2. 2IN to OUT: there should be no path
  3. 3Power on: voltage at the input
  4. 4Power on: output voltage