HDMI powering PC even when power cable unplugged?!

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metroplexomega

4 posts

Wannabe Geek

#69503 9-Oct-2010 12:38

Hi there

I have an interesting situation that's been occurring. I currently have both a PC and PS3 connected via HDMI (separate HDMI ports, no switches) to a LCD TV. However if I shutdown my PC and then power on my PS3, the fans and fan lights on the PC become active. Even if I switch off the power pack or even pull out the power cable, the fans keep going and the lights too, but the rest of the PC don't function.

I would not normally have seen this issue, but periodically I would hear an alarm ringing for a few seconds and stop while the PC was off. I thought it was my alarm clock playing up, but then discovered it was my temperature alarm inside my PC going off randomly although the PC was off.

I found if I unplug the PC's HDMI cable the activity stops. As soon as I plug it back in, the fans light up again. This only seems to occur when the PS3 is on.

The PC seems to still work fine, no real issues, but just wondering if anyone has the same issue. And does anyone know whats going on? Here's my setup:

AMD Phenom II X4 810 @ 2.6 GHz
MSI 770-C45 M/B
4 GB RAM
RADEON 4600HD PCI-E x16
Windows 7 Pro x64

Daewoo 37" LCD TV

PS3 80GB

sealdogfish

14 posts

Geek

#392988 18-Oct-2010 00:28

The hdmi cable carries 5V power over one of its lines and a ground. It seems in your case the 5V from the hdmi cable is powering your motherboard. Ofcourse it does not have nearly enough power to run the computer so only a few low current devices would run. Is it plugged into an onboard hdmi port or a seperate video card?

sealdogfish

14 posts

Geek

#392989 18-Oct-2010 00:29

The design flaw is most likely in the TV, not isolating the power from each of the hdmi ports

metroplexomega

4 posts

Wannabe Geek

#393338 18-Oct-2010 21:01

sealdogfish: The hdmi cable carries 5V power over one of its lines and a ground. It seems in your case the 5V from the hdmi cable is powering your motherboard. Ofcourse it does not have nearly enough power to run the computer so only a few low current devices would run. Is it plugged into an onboard hdmi port or a seperate video card?

Interesting information, thanks. BTW It is plugged into a separate video card on the PCI-E x16 slot. I now either keep the PC running or unplug the HDMI cable whenever I have the PS3 running, this seems to stop the problem with the temperature alarm bell ringing.

joeksemail

78 posts

Master Geek

Trusted

#399043 2-Nov-2010 11:46

Might be a lonbg shot but have you tried updating your BIOS?

metroplexomega

4 posts

Wannabe Geek

#399177 2-Nov-2010 15:44

BIOS is all up-to-date. I think sealdogfish may have the right idea about the TV not isolating the power from the HDMI properly. I would be interested if someone else with a HDMI capable PC and PS3 could try plugging in both devices to a HDTV to see if they can replicate the problem.

sealdogfish

14 posts

Geek

#399238 2-Nov-2010 16:53

If you want a cheap solution, just open up a small part of the hdmi cable and cut the +5V wire (on the hdmi cable that goes to the pc) the tv should supply its own power and only the grounds need to be connected (try it on a cheap hdmi cable)