MacBook Pro Screen Flickering when using HDMI to VGA adapter to connect to external monitor
The MacBook Pro's HDMI port has a DVI-D implementation. This means it has no analog signal, which is what VGA relies on to connect. More information here: apple support forums . Apple supplies an HDMI to DVI adapter, which could solve your problem if your monitor has a DVI port. If not, then I would suggest getting a Thunderbolt (Mini DisplayPort) to VGA cable, then using the Thunderbolt port on your Mac to link to your monitor instead.