Troubleshooting SMPS – 3 Winning Ways to Troubleshoot Faulty SMPS

Published: 13th September 2010
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My "SMPS repair mentor" said this to me: "restoring linear power supplies is easy, but troubleshooting SMPS is much, much more fun!"

I can’t agree more with him. Indeed, troubleshooting and repairing switch mode power supplies is more fun, but I have to warn you though…

If you don’t know what you’re doing, then things will get very, very frustrating because the circuit designs in SMPS are quite complicated.

But don’t you worry now…

I’m going to give you some essential tips for troubleshooting SMPS. These tips I learned from my repair mentor. You know, he actually created a step by detailed step manual on fixing SMPS.

The downloadable manual contains lots of easy to follow photo intensive instructions so if you’re interested in it, just follow the link shown at the bottom of this article.

Okay, no more rambling. Here are some essential tips to help you troubleshoot an SMPS unit successfully.

Note: I assume you already know how to read schematic diagrams of SMPS, and you know full well about each and every component in different types of SMPS. If you don’t know all these, then I recommend you check out the link above.

First Tip

So you have a faulty SMPS on your repair table… First thing you should do is study that particular SMPS unit. Specifically, study its circuit design. Doing so enables you to approach the problem from various angles.

Second Tip

Get all the necessary tools ready. Most novice technicians would have a volt-ohm meter for testing purposes, but that’s not sufficient!

I recommend other repairing and testing tools e.g. isolation and variable transformer, AC ammeter, blue ring and blue ESR meter and also oscilloscope.

Third Tip

Once you’ve removed the casing, I want you to monitor the components carefully. See, when troubleshooting SMPS, two of the most common problems I encountered were decayed glue and high voltage transformer that had too many dry joints.

Also if you’re dealing with a faulty SMPS that uses controller IC, use your oscilloscope. It’s ideal for high output voltage, power shutdown or power pulsating/blinking problems.

Trust me, troubleshooting SMPS is FUN but you definitely need a handy reference guide if you lack experience. Here’s a 271 pages SMPS repairing guide which is full of easy to follow photographic instructions.

Go to for fast and easy access.

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