This document provides a simple method for troubleshooting and repairing switch mode power supplies (SMPS). The key steps are: 1. Discharge filter capacitors and remove the transformer to access primary and secondary components. 2. Test secondary components like diodes and capacitors, then check the feedback circuit. 3. Move to the primary side by desoldering components one by one to identify faults. 4. If the primary side checks out, suspect the power IC and replace it to potentially repair the SMPS. Additional faults can include multiple bad components, dry joints, cracks or decayed glue.

1. Simple and Powerful Method To
Troubleshoot And Repair Any Types Of SMPS

2. Figure- Discharge The Big Filter Capacitor With A 2.2 K Ohm 10 Watt
Resistor Before You Start To Test On The Primary Side Components

3. • Next, remove the switch mode power transformer from the
board so that you could clearly see the primary and the
secondary section of the power supply.

4. • Test on the components in the secondary section such as the
secondary output diodes and the filter capacitors as seen in
figure below.

7. • Once you have confirmed all the diodes are good, the next
test will be on filter capacitors (electrolytic capacitors).

8. • if all filter capacitors are tested good, you can begin to check
on other section which is the Feedback circuit. check all the
electronic components in the feedback circuit.

9. • Now, you have completed
checking the components in the
secondary side and let’s move on
to test the components in the
primary side of the power supply.

10. • Checking the primary section is easy, just
solder out(remove at least one lead) all
of the electronic components and test
one by one until you have found the bad
or the defective components.

12. • If you did not find any bad components
in the primary section, then suspect the
power IC. Directly replace the power IC
and retest again the power supply.
Usually the power supply will work since
you have confirmed all of the primary
and the secondary component are good!

14. • Do you know that it can be more than one bad
component in the power section?
• You will find lots of components burnt especially
if the power supply hit by lightning or by a power
surge. The fuse, bridge rectifier, current sense
resistor, power FET, zener diode and power IC
could blow and this will usually takes you about
an hour or so to complete the troubleshooting
job.

15. Besides electronic components, you
are also required to check for
• Look For Dry Joints In A Circuit

16. • Check That The Board Did Not Crack

17. • Decayed Glue Found In Circuit Board