We pull the broken spring, match it to the door's actual weight and lift style rather than assuming the replacement should be identical to what failed - if the original spring was undersized for the door (common enough on builds from the early 1960s, before manufacturers standardized spring charts), we size up instead of repeating the mistake. On extension-spring doors we add or replace the safety cable through the spring if it's missing, since that's the piece most likely absent on original installs here. On torsion setups we check the shaft, bearings, and cable drums for wear before calling the spring the only problem - a worn bearing plate will eat a new spring's lifespan if we leave it alone. We test the door's balance by hand afterward: it should hold position at waist height with the opener disconnected. If it doesn't, something else in the system is still off, and we won't call the job done until it does.