Question Network speed issue


Active Member
I need ideas on this one!

So built myself a new PC yesterday. All running well etc apart from one issue, when its switched on my whole network crashes to around 50% speed, as soon as i shut it down the speeds bounce back up.

The PC only needs to be switched on (nothing else connected, no ethernet etc.) to kill the network.

PC off (testing on laptop)


PC on (only power connected, testing from laptop)


Wondering if anyone else has experienced anything like this?


Distinguished Member
That's an internet speed test, so don't rule out it affecting the stuff related to that instead of your network. Did you test over wi-fi or ethernet?

I'd start by narrowing it down. Is there any networking or internet equipment sitting next to the PC? Interference is most likely if they're close together.

If you tested over wi-fi then try removing the PC's wi-fi card to see if that makes any difference.

It sounds like it could be related to the mains, do you have a spare power supply you could try?


Distinguished Member
If only power is connected, that suggests that the power supply is dropping a lot of noise onto the power line.

Are you using any Powerline or similar devices to support your network?

What power supply / PC build are you using?


Active Member
Cheers for replies, just an update all is sorted.

I know I used internet speed as an example as it was the easiest to show.

I believe it may have been a bad ground causing noise issues as once I'd reseated everything connected to the PSU it's happy and working a treat.

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