Protect devices from AC current

Thread Starter


Joined May 23, 2021
Is it true that when we connect electrical appliances such as televisions or computers to the wall or unplug them, they may be damaged and it is better to always be in the wall?
Of course, I use a keyed tee, but does having a key have an effect on this?
Somtimes when I turn off the computer from tee switch (after complete shutdown), some of the LEDs on my computer parts turn on and off for a moment! This can be harmful? What can I do to prevent it? Is there a way to protect this?


Joined Dec 2, 2017
It is not true, because you should always connect and disconnect appliances with the power switch off.

The only real danger from removing power after a PC shutdown is if it has a faulty BIOS battery.


Joined Nov 6, 2012
There is some truth behind that theory ........
Powering-up an Electronic-Device does create additional stress on certain Components.
If those Components are already under a heavy-Load, or over-heated from previous use,
during power-up is when they are most likely to fail.

Rapid and repeated interruption of Power is probably the worst thing You can do to an Electronic-Device,
however, a very well designed, high-quality Device
will probably never be adversely affected by this type of abuse.


Joined Jan 23, 2018
This is an interesting question, I would really wonder what the original thinking in either direction was.
Certainly it makes a lot of sense to have a device switched off before plugging it in, to avoid making and breaking connections under load. And constant plugging and unplugging does put some wear on the plug and the outlet.

Yanking the cord to unplug a device is a separate case that will usualy cause failure eventually.

BUT if the device is switched off there is no rational way for it to be damaged by unplugging and re-plugging.

Some devices do not have an off/on switch and thus are constantly drawing some power when plugged in, and are totally exposed to unfortunate power line spikes that do happen very rarely. An example is an external power supply for a cheap desktop computer that was damaged by a serious lighting event. A nearby computer that had the main switch OFF was undamaged. But how often does lightning strike a utility pole in a given area?