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 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.