Hard drive light on even after shutdown

[mike45450]

I have a second PC that is having a strange problem with it's HD light. When it's turned on, the HD and the light act normal. But when i shutdown the PC, the light is constantly on, not blinking or anything. The problem started after i changed the CPU heatsink/fan, but i don't see how this would affect it.

[Seedler]

Hm maybe you accidently connect the wrong cables?:blink: check the power cable and HD activity light cable.

[Mr. Mulder]

"Captain, I think we should reverse the polarity on them first."

[suprafreak6]

Yeah Mr. Mulder is correct...flip the wire going from the harddrive led to the motherboard because if it is flipped that can cause them to stay on all the time...

[clocker]

Yeah Mr. Mulder is correct...flip the wire going from the harddrive led to the motherboard because if it is flipped that can cause them to stay on all the time...
It can?
I've never seen that happen.
Usually (meaning always) if the polarity is reversed the HDD activity LED just doesn't work at all.

[thewizeard]

..a led is a sort diode you see...

[suprafreak6]

oh well it happened on one of my computers...i flipped it and it worked fine

[truetejas]

Thanks for the tidbit .... now I can say I learned something today :D

[Chewie]

Being a diode, an LED alloiws current to travel in one direction only, and therefore only works when connected the right way round.

If it's lit up all the time then it's getting power when it shouldn't.

I have seen this once before on an A7NX-X but never really investigated it as the owner wasn't bothered by it.

[Appzalien]

The motherboard power light is the only led that stays on after shutdown, somehow the HDD is getting that signal. Recheck your connections for the cpu fan and make sure you put it on the right connector and in the right direction. Are you absolutely sure this mobo is compatible with the new cpu? Like a Celeron or Celeron D would fit the socket but are not the same so the mobo's instructions might have changed because they use different instruction sets for different chipsets.

[lynx]

There are two ways these led's are switched on, depending on the board design. Both methods use the +5v supply to power the led. The diagrams show the state when the led would not normally be lit.

The first method is that both anode and cathode are at ground level when the led is off, and the anode voltage is raised to turn the led on.

5v─────┐
/────┐
gnd────┘ │ anode
led
│ cathode
gnd─────────┘

The second, simpler to implement, method is that both anode and cathode have raised voltage when the led is off (no voltage difference=no current flows so the led stays off), the cathode voltage is dropped to turn the led on.

5v──────────┐
│ anode
led
5v─────┐ │ cathode
\────┘
gnd────┘

If the board uses the second method then obviously when the board is powered off then both anode and cathode are at ground level.

gnd─────────┐
│ anode
led
gnd────┐ │ cathode
\────┘
gnd────┘

If the anode is connected to +5v standby then the lamp will light when the board is powered off (since the cathode is now at ground).

5vsb────────┐
│ anode
led
gnd────┐ │ cathode
\────┘
gnd────┘
However, it will operate normally when the board is powered on.

5vsb────────┐
│ anode
led
5v─────┐ │ cathode
\────┘
gnd────┘
I can't think of any other scenario which would allow the led to operate normally when powered on.