Cleaning the air filter is the best action to resolve the issue of a projector that shuts down after fifteen minutes of use. A dirty air filter can cause overheating and trigger the projector's thermal protection mechanism. Replacing the video input cable, changing the bulb, or swapping the power cord are unlikely to solve the overheating issue.

The first step a technician should take before upgrading the Wi-Fi card on a laptop, or performing any internal hardware modifications, is to remove the power cable to ensure the device is not powered on. This is a crucial safety measure to prevent any electrical damage to the laptop or the technician. It also helps in avoiding any unintended changes or data loss that might occur if the device is powered on during the upgrade process.

Since the on-premises email server has been decommissioned and users are experiencing issues with scan-to-email functionality, the best solution would be to configure an email relay. An email relay server can accept emails from devices like printers and forward them to the correct destination (such as a cloud-based email service). This avoids the need to bring back the old server or set up a new one.

An inverter is a component that converts DC power to AC power for the backlight of an LCD (liquid crystal display) screen. If the inverter is faulty, the screen may appear dim or dark, even if the brightness settings are adjusted. Replacing the inverter may fix the issue. The LCD itself, the video card, and the digitizer are not related to the screen brightness problem.