Why not to hot swap a keyboard.

[wippid1]

I've been told that its bad to hot swap a keyboard or a mouse. I personally have been doing it for years and have had no problems. I have looked online for answers but the information I have found is very vague. If it is true that you can blow your motherboard by hot swapping a keyboard out mouse, I would like technical data on why and how it happens. Thanks for the help.

 

[edfair]

Things like the data line going high when the 0v line disconnects before the +5 line. And other assorted misapplied voltages.

Yes, you can blow them.

This doesn't apply to serial mice. Those drivers on the M/B are designed for signal voltages withall sorts of glitches available on the lines. But I can't speak for the mice.

Lost one a year and a half ago where it was cheaper by a thousand dollars to replace the system and upgrade the OS than to buy a replacement M/B. Or could have had it fixed for 280.00 with a 3 week turnaround.

Ed Fair
Give the wrong symptoms, get the wrong solutions.

 

[cdogg]

I remember being told the same thing way back before ATX configurations were ever released. Perhaps it only affected AT and early ATX systems? Who knows? All I can say is that I too have been doing it for years and never had a problem...

~cdogg
[tab]"All paid jobs absorb and degrade the mind"
[tab][tab]- Aristotle

 

[SkipCox]

Most of us have cdogg...but you likely know that one bit of transient electricity can do a lot of damage; especially on one of the +dcv rails.

Gotta admit I cringe when flipping the switch on my mechanical KVM.

Skip

http://scc.i8.com

 

[bcastner]

http://support.microsoft.com/default.aspx?scid=kb;en-us;816843

 

[cdogg]

bcastner,

I don't think the user was referring to USB devices. Instead, the phrase "doing it for years" seems to indicate older PS2 or serial devices, though they never did state that for sure.

 

[bcastner]

cdogg, you are of course correct.
What is odd is that fair number of computers supply power to the PS/2 ports even when shut off. It seems if a power spike of some kind was worrisome, there would be nearly no safe condition for swapping the mouse or keyboard.

See, for example:

http://support.microsoft.com/default.aspx?scid=kb;en-us;325975

 

[edfair]

As a matter of course I pull the power cord on those machines that keep power alive. And the way they are built now, that is just about every time.

 

[cdogg]

edfair,
This seems to be your area of expertise, so I thought I'd ask:

When a PC is off and unplugged from the AC outlet, isn't there still some small amount of current being pushed from the power supply to the motherboard? I remember reading somewhere that the capacitors in most power supplies hold such a high charge that some must be dissipated by means of the motherboard. Is there any truth to that? And if so, wouldn't that mean PS/2 ports are adversely affected?

Thanks in advance,

~cdogg
[tab]"All paid jobs absorb and degrade the mind"
[tab][tab]- Aristotle

 

[edfair]

The capacitors for the voltage rails of the PS probably are drained to unmeasurable amounts in 3 to 4 seconds max. +5 would probably be gone faster than that. Those times I've had an analog meter on the +5 it has reached the 0 before the eyeballs could get shifted over.
The power supply filter capacitors probably decay slower once the voltage has dropped to below the point where the switching has stopped but they are designed to drain down too.

Ed Fair
Give the wrong symptoms, get the wrong solutions.