Showing posts with label switched mode power supply. Show all posts
Showing posts with label switched mode power supply. Show all posts

Wednesday

SMPS Board with No Power - Short Circuit and Voltage Surge Can Cause SMPS Failure

SMPS stands for Switched Mode Power Supply. It is the essential power supply unit (PSU) in electronic devices ranging from laptops to printers, LCD monitors to camcorders and plasma televisions.

When you get a SMPS board with no power, check the fuse on the board. If it has blown to a dark color then clearly, there's no power flowing through it.

A direct short circuit or power surge can cause SMPS failure. In fact, it is one of the most common reasons for failure. Sometimes, you might also hear an audible whine with low output voltage when this happens.

To fix this problem, first glance through the rest of the components on the board to see if a simple fuse replacement will do the job. Sometimes, the varistor and other components may have been shorted too, so it is better to use an ohmmeter for testing.

LCD TV SMPS Repair - 3 Reasons For The Buzzing Transformer Noise when the SMPS is turned on

I was recently repairing a 200W SMPS board of a LCD TV where the power supply had been restored to a certain extent using some nifty schematics.

Burned power supply (blown fuse) is one of the common reasons for SMPS failure, and without the right schematics, it can be a nightmare to find the cause of the problem.

When I turned on the power I heard a buzzing sound (noise) from the transformer. It was like a high whine...an expected yet annoying sound that needed to be fixed. And the way to fix it is to first look for any visible damage across the SMPS board.

Usually, there are 3 reasons why you're hearing that buzzing sound:
1. Bad filter caps on the input side
2. Bad diodes, leaky capacitors or bad optocouplers
3. Loose parts on the transformer that vibrate because of the transformer's magnetic field.