nice completed SERVICE MANUAL as the description THANK YOU !!!-
Text excerpt from page 106 (click to view)
General Troubleshooting Guide
201B4 M25P 99 Go to cover page
17 A buzzing sound when powering on
This sound is caused when the auto degaussing circuit is active. This buzzing sound is normal when the monitor is first turned on. This sound may be louder during the winter months and during initial power on.