Keyboard and USB Hub have lights - PC not connected to wall plug

pepp77 · 22 Sep 2023 at 09:26

Hi

As per title, last night I was playing around with my BIOS and changed a setting I shouldn't have which resulted in no boot. I fixed it with a CMOS clear, but noticed that when I turned the PC off, turned the PSU off and then unplugged the power cable, both the keyboard and USB hub were still showing lights on them when connected to the PC with no power going into it.

How can this be?

raralis · 22 Sep 2023 at 09:49

Residual power?
Happens with my rgb mouse and keyboard too for a few seconds after the pc is powered off.

pepp77 · 22 Sep 2023 at 09:53

How about after 6 hours?

Jamin280672 · 22 Sep 2023 at 11:19

pepp77 said:
How about after 6 hours?

It's 5 volts with next to no current draw, I wouldn't want to touch the capacitors in my PSU even after 6 hours, I've had one blow before in a leadtek superflower 1000w platinum and it was a like a bolt of lightening, PC hadn't been on all day.

pepp77 · 22 Sep 2023 at 11:29

It just freaked me out, after unplugging the PC, I pressed the power button in to "discharge" as they recommend and then went to bed after removing the CMOS battery, it was only when I woke up and noticed the Scroll lock light was still on on the keyboard that I was like eh?

It also didnt help that after putting the battery back in and turning the PC on it still hadnt cleared the BIOS. I had to remove the battery, remove the power, remove the keyboard and USB hub then I left it for an hour whilst I did other things, then I also shorted the CMOS pins and this time it reset the BIOS ands started working.

Werewolf · 22 Sep 2023 at 13:09

IIRC the CMOS can hold data for a while after the battery/power is removed, hence the cmos clear pins.

Mr Evil · 22 Sep 2023 at 13:22

Was the monitor still plugged in? Monitors sending power the wrong way is something that can happen.

pepp77 · 22 Sep 2023 at 22:36

Werewolf said:
IIRC the CMOS can hold data for a while after the battery/power is removed, hence the cmos clear pins.

Hadn't considered that, but the manual did say the battery should only need to be removed for 1 minute to clear the CMOS.

Mr Evil said:
Was the monitor still plugged in? Monitors sending power the wrong way is something that can happen.

2 Monitors connected via DP were still connected, can DP cables carry power?

One thing I thought it could have been was I have a switch that's half POE and maybe the PC is connected to a POE port, but I'm not getting on my knees again to check