I have a samsung surround AV receiver system HT-AS720S & it keeps shutting itself off & says Protection on display.

SOURCE: SAMSUNG HT-X50

I've had the same problem. I smelled something burning, PROTECTION came up on the display, and the sytem shut off. Initially, I thought it just overheated, so I turned it off for the night and tried it again in the morning. It stayed on for about half an hour, then the same problem occurred, without the burning smell. I called Samsung, they said the "fan was out," but that doesn't explain the smell. I wanted to check for myself, so I opened the casing, and indeed found a burnt metallized polyester film capacitor. Samsung obviously did not consider the heat level that could get through it, and thus used the wrong type of capacitor. I'm sending it back to get serviced, hopefully it will come back with a different capacitor.

SOURCE: powering off for protection samsung HT-WX70

the fan is broken on your unit, this is a feature to keep the unit from over heating

check if there is anything blocking the fan from moving/rotating

try to contact your manufacturer

SOURCE: Samsung HT-X40 also shuts off after displaying Protection

You probably have the same problem that myself and several others have had, and let me guess, its outside of the warranty? How good are you with a soldering iron? If you are not afraid to do some soldering you can fix it, check out these instructions that i found:

http://lemurt.wordpress.com/2008/08/18/defenition-of-waranty-void/

you will need 474k or .47uf 100v capacitors and a soldering iron, but you can fix it, worked for me.

SOURCE: my samsung dvd surround system ht x40 shuts off by

check your speaker connections for shorts or touching wires

SOURCE: everytime I turn my on samsung ht-q70 the display

The amplifier has a bad channel, or is bad itself. It is trying to either output too much current or is not putting out enough. If you have multiple speakers wired to one channel, you will either have to change the wiring to series(unit positive to first speaker red, first red to second BLACK, second red to unit negative) or remove on speaker. (If this is the case, then you might want to look at this. It is a tip/rick to place and properly/successfully run three subwoofers, but the main concept can be used on all channels.) If all channels are wired to he correct speaker, then the amp is in fact at fault.