How to Troubleshoot & Replace Samsung AP4579971 / DE26-00122B Microwave High Voltage Transformer

Replaced transformer... This Youtube video captured the exact sounds my microwave made.... https://www.youtube.com/watch?v=CF0RXKF4puQ A little background: this microwave has been buzzing like this for just over a year now... it was about 2 yrs old, when one day, it wouldn't turn off when the door was closed... the unit would not respond to any of the control panel button presses. Eventually I simply pulled the plug for a few minutes, and when plugged back in, everything was normal... Except it started making a loud buzzing when heating anything... the noise level never changes even when changing the power-level or time. Everything seemed to work normally except for the buzzing. The unit is an over-the-range model, and not the easiest to remove and open up, so I simply left it for the past year, thinking I would have it fixed if it got worse... it never did. Eventually I found instructions to remove and fix the unit... found and ordered the hv-transformer from this site and replaced. Pretty simple diy repair (I have a background in electrical/electronic h/w and repair); noise gone and it works like new now. 

R&r transformer 

Researched on the interwebs & found likely solution to be transformer replacement. Ordered transformer, received transformer quickly and installed with no problems. 

Removed cover and found burn mark on transformer. read up on how to repair it. then ordered parts from appliancepartspro.com 2 days later all fixed. Saved $350 on a replacement microwave! 

Replaced transformer with new one and sound was gone! I was pretty sure that the sound was coming from the transformer, but was not 100% certain (difficult to tell, even with the cover off). The primary windings on the old transformer looked like they had been hot, but wasn't sure if that was normal or not. The new transformer was essentially silent. All we can hear now is the fan. Great fix for an otherwise good microwave!