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Computer picking up interference from other electronics? Answered

I have a weird problem: when I turn off my floor fan, my computer wakes up from standby.
I have tried a different fan, similar problem happens, except when I turn on the fan.
I have previously ignored this problem, but my computer started acting weird and eventually failed completely.
I found a bunch of capacitors in my PSU are blown. I recapped and it's working again.

What is causing the problem, and are there some fix? (not using a fan is not an option)

My setup: outlet <- cheater plug <- power strip <- everything else
                                                                     ^
                                                            power strip <- fan
The second power strip is used due to length constraints. Here at college dormitory each student only get one ungrounded socket, hence the cheater plug.

Discussions

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Samiran

3 years ago

inductive loads like Fan can induce Harmonics for your Computer. Use of proper Ground should be there. CPU or PSU must have a Earth or Ground.

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Downunder35m

3 years ago

Apart from obvious ground and interference problems from your fan:
A good electronic device can be certified to different criteria.
For example the CE and TÜV signs indicating it is electrically safe.
But a more important cert is that the device in question neither causes electrical interference nor that it produces it !

In your case, assuming the house and devices you have connected are up to code:
If the PC power supply, the connected modem/router or the mainboard itself has troubles filtering out interferences all things bad can happen.
You said you replaced blown caps - do you realise that the blown caps could have already caused further damage?
There is one thing you can try.
Get a power board with filters and use it between mains and PC quippment.
It will do the filtering for you and good ones also include filters for the phone and ethernet cables - not always cheap but IMHO your best buy now.

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AnonymityDownunder35m

Answer 3 years ago

I thought power strip with filters only filter external interference like lightning, not from other electronics on the same strip?

The capacitors I replaced are all on output filter side. I'm not sure about further damage but it has worked without problems for 3 months since the repair.

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Downunder35mAnonymity

Answer 3 years ago

If you only connect the computer and the related hardware to it, everything else like motors in a different power plug should no longer affect the PC.
But it might be easier and cheaper to just buy a decent PSU for your PC.
Even if you just borrow one from a friend's PC you can check if the problem persists or not.

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verence

3 years ago

Ungrounded plugs? A disaster waiting to happen. Are there no building codes to avoid that crap?

Anyway, yes, spikes generated by switching on/off devices may trigger spurious signals on data lines. The fact that the devices are not properly grounded doesn't help.

You can try ferrite core(s) on the cable to the fan and/or to the computer. And you can try to switch of the wake on keyboard/mouse/... in the BIOS. Of course you will have to start your computer by the switch.

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steveastroukverence

Answer 3 years ago

US code, assuming that's where the OP is DO now have grounded outlets mandated by code. There is a lot of old, ungrounded, stuff out there.

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Anonymityverence

Answer 3 years ago

There probably is, but it's not like I can do anything about it.

Ferrite core sounds right. I will try it out when I find one.

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Josehf Murchison

3 years ago

Bad wiring in the receptacle box, the receptacle box itself is not grounded. This happens in old code wiring and sometimes the ground to the box has come loose. If the ground in the receptacle box is loose tighten it, if the receptacle box doesn't have a ground, you need to find an external ground. Tread carefully that receptacle will kill more than your electronics, IT CAN KILL YOU WITH NORMAL USE.

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AnonymityJosehf Murchison

Answer 3 years ago

There are only two wires in the receptacle box. External ground, how? One method I have heard is to bury a cable deep into soil. Not something I can do at dormitory.

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Josehf MurchisonAnonymity

Answer 3 years ago

Another way is to connect to pluming or a heating radiator. Depending on where you are it is a 40, 50 or 60 cycle interference you can build a filter to a false ground. If not a mains hum you can measure the interference and do the same.