Cleeds is correct. When equipment manufacturers put a power cord on with a third prong, they really want you to ground their unit. Not doing so creates a safety hazard, sometime a lethal one. Yes, if something internal fails or breaks you can have 120VAC line on the chassis, but that is not the issue of what I saying. Internal equipment can "leak" line current through parasitic capacitance, mutual coupling, etc. which will put some AC voltage on the chassis. Touching an ungrounded chassis with a real ground will run that current right through you.
When you work around electronics and electricity long enough, you will get zapped sooner or later. Early in my EE career I discovered just how conductive concrete is. I got seriously zapped just from this, not plugging a power supply ground into a grounded outlet and standing on concrete.
The problem with that third prong is sometimes they get plugged into a different outlet than the rest of the equipment and you get a ton of hum. There are a number of reasons for this but do what Cleeds stated - get all the grounds at the same potential. The easiest way to do this is to power everything from one outlet box and use that ground for everything.
When you work around electronics and electricity long enough, you will get zapped sooner or later. Early in my EE career I discovered just how conductive concrete is. I got seriously zapped just from this, not plugging a power supply ground into a grounded outlet and standing on concrete.
The problem with that third prong is sometimes they get plugged into a different outlet than the rest of the equipment and you get a ton of hum. There are a number of reasons for this but do what Cleeds stated - get all the grounds at the same potential. The easiest way to do this is to power everything from one outlet box and use that ground for everything.
