Next Generation Emulation banner
1 - 9 of 9 Posts

·
NextGenerationGaymulation
Joined
·
2,934 Posts
Discussion Starter · #1 ·
This is kind of weird!, but even after I turn off my computer there's still a strange blue LED on that lights it up like lantern at night... my current solution is to pull the plug at night! Now I can't find a connector for that blue LED to pull out on the mobo.

Does anyone have any ideas what could cause this very wierd problem?
 

·
Miserable Bugger
Joined
·
1,094 Posts
get a bit of Blutack over the LED so you can't see it.

That'll solve the problem until you figure out what is is.

Are you sure though that your PC is actually powering down and not just going into Standby or hibernation?
 

·
-PM to advertise here-
Joined
·
8,320 Posts
Well, I've got a green LED on my mobo which stays on even after I shut off the PC. It goes off when I switch off my PSU from outside.
 

·
NextGenerationGaymulation
Joined
·
2,934 Posts
Discussion Starter · #5 ·
The LED sits on the mobo, the computer doesn't go into standby or hibernation, it's really turned off. I don't have the kind of PSU that you can switch on/off from outside on this comp.

I suspect that there's a small current even after I turn off the computer making this LED to glow. I've had that same problem with a older computer, and if the charge was high enough it could even cause the computer to turn on. ( That one didn't have a LED though ) but I could switch of the PSU from outside.

It's not a big problem, but it'd still be intressing to know the cause.
 

·
Registered
Joined
·
340 Posts
Like fireblaster said, check your motherboard manual. I know of a few motherboards that have leds built into them to show that it is getting power. There is supposed to be some power going through the motherboard.
 

·
Registered
Joined
·
7,425 Posts
Yeah. The small current is called the 5v Standby.

Here's a bit of info from http://www.pcguide.com/ref/power/sup/funcSoftPower-c.html

"Early PCs using the PC/XT, AT, Baby AT and LPX form factors all use a mechanical switch to turn the computer on and off. Newer form factors, starting with the ATX/NLX, and including the SFX and WTX, have changed the way the power supply is turned on and off. Instead of using a physical switch, these systems are turned on by a signal from the motherboard telling the power supply what to do. In turn, the motherboard can be told to change this signal under software control. This is what allows Windows to shut the power down to a PC, or what allows such features as turning a PC on from a button on the keyboard. This feature is called "Soft Power" and the signal that controls the power supply is called "Power On", or alternately, "PS On" or "PS_On".

This feature would seem to create a small "chicken and egg" situation however. How can the motherboard tell the power supply to turn on, electronically, when the motherboard is also off due to not having any power from the supply? :^) The answer is the other "Soft Power" signal, which is called "+5 V Standby" (or "+5VSB", or "5VSB", etc.) This signal is the same output level as the regular +5 V lines from the power supply, but is independent of the other provided voltages and is always on, even when the rest of the power supply is turned off. A small amount of current on this wire is what allows the motherboard to control the power supply when it is off. It also permits other activities that must occur while the PC is off, such as enabling wakeup from sleep mode, or allowing the PC to be turned on when activity is detected on a modem ("Wake on Ring") or network card ("Wake on LAN")."
 
1 - 9 of 9 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top