Troubleshooting a 12 V adapter with no output
High risk: mains voltageAbout 60 minutes
High risk: mains voltage. Unplug the device and remove any battery before opening it. Stop at any step you're unsure about.
Step-by-step troubleshooting of a 12 V adapter with no output: fuse, MOSFET, main capacitor, controller IC and output diode checks, safe discharge and the series bulb test.
What you need
- ☐ Multimeter (CAT II, 1000 V DC range)
- ☐ Alligator clip test leads
- ☐ Soldering iron and desoldering pump
- ☐ 10 kΩ 5 W discharge resistor
- ☐ Insulated pliers
- ☐ 60–100 W incandescent bulb and socket
In this guide
- 1Get to know the inside of the adapter
- 2Discharge the main capacitor
- 3Inspect visually
- 4Measure the output and the fuse
- 5Test the MOSFET and the bridge rectifier
- 6Measure the main capacitor and the controller supply
- 7Test the output diode
- 8First power-up with a series bulb
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You carry out the steps in this guide at your own risk. Opening a device that is still under warranty may void it.