When changing the magnetron tube (or any other internal component) inside a microwave, it's generally recommended to allow some time for any residual electrical charges to dissipate before using the microwave again. This is a safety precaution to avoid potential electrical hazards.
The amount of time you should wait depends on the specific microwave model and the manufacturer's guidelines. In many cases, waiting for about 5 to 10 minutes after the magnetron replacement should be sufficient. However, it's essential to refer to the microwave's user manual or follow the instructions provided by the manufacturer.
Additionally, when working with microwaves or any electrical appliances, it's essential to follow proper safety procedures, use the right tools, and, if you're not familiar with appliance repair, consider seeking professional assistance to ensure the replacement is done correctly and safely. Mishandling microwave components can be dangerous and may lead to malfunctions or electric shocks.