How to Check an Instrument's Voltage Limiter

A voltage limiter, or voltage regulator, is an electronic device inside an instrument or motor that limits and stabilizes the voltage output needed in order to prevent electrical shortages or other problems. On motors, the voltage limiter works at 12 volts. However, on smaller electronic instruments like radios, DVD players or other electronic devices, the standard power supply voltage is approximately five volts. Voltage limiters, or regulators, can be tested at home with a digital multimeter.

Things You'll Need

• Philips-head screwdriver
• Multimeter

Instructions

1. Remove the case screws holding the case on the electronics device having the voltage limiter that will be tested. Remove the screws with a Phillips-head screwdriver, set them aside and gently lift the case off the instrument.

2. Locate the voltage limiter inside the instrument. The limiter will be situated close or right next to the power supply.

3. Turn the multimeter to the "On" position and set it to the voltage setting at the 9-volt range.

4. Place the negative test lead against the ground terminal pin on the voltage regulator

5. Place the positive meter lead to the output voltage terminal pin. If the meter reading falls below or above five volts, the voltage limiter is bad and should be replaced.

References

• Foundations of Analog and Digital Electronic Circuits; Anant Aqarwal and Jeffrey Lang
• Repair FAQ: Notes on the Troubleshooting and Repair of Small Switchmode Power Supplies