Fan Being Powered Through HDMI Cable

Simsmax · Dec 11, 2015

Fan Being Powered Through HDMI Cable (with power supply totally disconnected!!!)

This is happening to me, exactly like this: https://www.youtube.com/watch?v=-5ZeFr-Acas
(but with different specs)

This can cause any harm to my hardware long-term?
Should i worry about?

Let's discuss about it?

makkem · Dec 11, 2015

Hi
Is your power supply completely unplugged from the wall ? ( PSUs maintain 5V to the motherboard )
Does the cpu fan run at full speed ? ( The voltage in an HDMI cable is 5V)
Is the HDMI cable plugged into a TV or a monitor ? (TVs have extra functionally and can use more pins in the HDMI than monitors)
It's unlikely to cause long term problems as I suspect if it was going to damage something it would have done so straight away especially given the probable 5 V voltage.

Simsmax · Dec 11, 2015

Is your power supply completely unplugged from the wall ?
YES

Does the cpu fan run at full speed ?
checking soon

Is the HDMI cable plugged into a TV or a monitor ?
YES, when monitor power is turned off, the fan stops (clearly the energy comes from the monitor through HDMI)

i have searched on google and youtube, found only the video reference, nothing more, sounds like this is a bit rare to occour. No one never saw this? it's kinda creepy...

makkem · Dec 11, 2015

Its obviously pretty rare so it may only occur with a specific combination of motherboard and monitor.
The monitor as you say is obviously providing power to the motherboard through the HDMI,which is strange as you would expect the power to be supplied by the PC.
Perhaps the monitor has CEC (Consumer electronics control) for instance to switch inputs automatically to the working device.this would have data and hence power on pins 13 and 17 and perhaps (for a reason I cannot guess at ) the motherboard has these pins connected to the cpu fan control circuitry.
It would be interesting to try it with a different make of monitor .
Do you have the HDMI plugged into the motherboard or into a graphics card ?
It may be worthwhile contacting the motherboard manufacturer to see if they have heard of this.
It certainly must be strange to unplug your PC and find the fan is still running.

Simsmax · Dec 12, 2015

The HDMI is plugged into the graphics card.

Maybe i can try with a different monitor (or TV), gonna test later.

makkem · Dec 12, 2015

This is peculiar,I cannot think that there is any connection between the GPU and the CPU fan.
There also should be no connection with the 5V that is on the HDMI and the 12V that powers the fan.

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Fan Being Powered Through HDMI Cable

Simsmax

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makkem

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Simsmax

Reputable

makkem

Distinguished

Simsmax

Reputable

makkem

Distinguished

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