So my girlfriend calls me. Her xbox360 controllers aren't connecting to the xbox.

Step 1 was to change the batteries. That didn't help.
Step 2 was to try a wired controller. That worked fine.
Step 3 was to unplug the thing, wait a few minutes, and plug it in. That didn't help.
Step 4 was to explain to her that the controller wireless dying typically meant a Red Ring of Death is imminent and to call Microsoft.
Step 5 involved listening to her bitch and moan about how shitty Microsoft is if their console can't last 6 months when her Super Nintendo is god knows how old.
Step 6 involved her plugging the xbox360 into another power strip, despite my protests that this is dumb and will help nothing because electricity doesn't work that way.
Step 7 involved me screaming "WTF?" because plugging into a different power strip fixed it
Step 8 was to insist that physics would not allow such things and to plug it back into the original power strip... Which caused the wireless controllers to not function again.


I am currently on Step 9, which involves my doubting everything that I know. The next time I'm over there, I'm going to assault that power strip with a multimeter and screwdriver until I find the cause of this insanity. The controller wireless simply does not work if it is plugged into that particular power strip (she recently moved the system to another location, and this was the first time she'd turned it on plugged into that strip)

There could be a problem with that particular power strip causing some kind of interference with the 360 controllers. Just the other day my grandma was having trouble with her phone line (loud hissing could be heard on either end of the phone and the dialup internet could not connect.) After an hour or so I discovered that her printer only had to be plugged in to cause the problem (not even connected to her computer.) I took it out and lent her an old spare and the problem is solved until we get her a new printer.

 Sometimes there are just the stupidest causes to problems I guess!

Maybe the difference between the two is that the second one is grounded* and the other one is not? That would be the only logical explanation. Because it's the only thing which could be different from the second plug without the xbox not functioning altogether.

*I don't know the English word for it, but its a literal translation from my language and mean "connected to the earth/ground" ergo it's 0V and can be used to prevent a metal case from frying you. 

Grounded is the right word. 

Electric circuits in households aren't as perfect as you might think. High frequency interference can be caused by em radiaton or badly designed appliances, who are less shielded from the power supply than they should be (usually cheap electronics). Since there are typically several isolated circuits in a house, the second type of interference usually stays within its circuit, and you get the type of behaviour that you describe.

That's a valid point. Frequency alterations can even be made deliberate by i.e. powerline networking. But still, a simple capacitor would filter that out, don't you think an Xbox has a few of those? :)

Kidding aside, wouldn't a rectifier negate/weaken this effect too? I still think it's very strange, especcialy when you think that 2,4 Ghz devices like the Xbox-controllers must be extremely interference-resistant, because it's a such heavily used band. (WLAN 802.11bgn, Bluetooth, DECT just tot name a few) 

Is there a microwave or cordless phone on the same circuit as her 360?

I remember debugging a neighbor's internet issues (internet explorer did not work, everything else did), when I setup my laptop the gateway (switch, router, NAT, wireless AP, firewall combo box) would stay online for all of ten seconds, moving the gateway to it's own outlet fixed it. It's usually the last thing you can think of. As for why IE didn't work their anti-virus was paranoid enough to block that troublesome explorer.exe (and a few others IE needs, can't recall at the moment) process from calling out of the box.

Weng:

she recently moved the system to another location, and this was the first time she'd turned it on plugged into that strip

Is it the new location rather than the power strip that is the problem?

 

It's usually the last thing you can think of.

Yes, I've noticed that.  The last thing I try is always the one that works.

 

El_Heffe:

It's usually the last thing you can think of.

Yes, I've noticed that.  The last thing I try is always the one that works.

I've noticed that too.  I think it's because once I find something that works, I stop trying things.

OP says it's a plug next to the other one, so I don't think that is the problem 

dtech:

OP says it's a plug next to the other one, so I don't think that is the problem 

Yes, however it isn't the same one as the other one.

dtech:

That's a valid point. Frequency alterations can even be made deliberate by i.e. powerline networking. But still, a simple capacitor would filter that out, don't you think an Xbox has a few of those? :)

Kidding aside, wouldn't a rectifier negate/weaken this effect too? I still think it's very strange, especcialy when you think that 2,4 Ghz devices like the Xbox-controllers must be extremely interference-resistant, because it's a such heavily used band. (WLAN 802.11bgn, Bluetooth, DECT just tot name a few) 

 

No all capacitors can deal with such high frequencies, especially if you want a cheap capacitor with fairly high capacitance (to compensate for bigger spikes). I'm not experienced in this field, but I beleive that a self resonance frequency of up to a couple of hundred Mhz is quite common amongst standard capacitors. There are of course capacitors who can handle this, but it's not certain that the Xbox has one of those at the power supply. It is more likely that the board containing the sender chip has one, but if the disturbance gets into the shielding box, it could easily propagate to the chip in question through EMI. The decoding logic is probably very resilient to interference, through frequency switching, checksums etc, but the chip itself can still be vulnerable. You are correct when you say that a rectifier usually contains low-pass filters, but the operating frequency of a switched-mode power supply is usually in the kiloherz range, and it is therefore probably not very good at surpressing GHz frequencies.

I'm guessing on a non earthed extension lead.  I've seen that cause a computer case to register ~120V before on a multimeter.  DIY Faraday cage anyone :D

 My guess is that she is just an idiot. That is usually the explanation for these problems that go against laws of nature...

 

My wife has an uncanny knack for ignoring any rules I put into place in our home.  I see no reason this wouldn't extend to the laws of physics as well.

bstorer:

My wife has an uncanny knack for ignoring any rules I put into place in our home.  I see no reason this wouldn't extend to the laws of physics as well.

I lol'd. 

belgariontheking:

El_Heffe:

It's usually the last thing you can think of.

Yes, I've noticed that.  The last thing I try is always the one that works.

I've noticed that too.  I think it's because once I find something that works, I stop trying things.

 

Can you explain that joke a little further?  I still don't get it... 

Obfuscator:

You are correct when you say that a rectifier usually contains low-pass filters, but the operating frequency of a switched-mode power supply is usually in the kiloherz range, and it is therefore probably not very good at surpressing GHz frequencies.

 

 

Actually, a simple RC low pass filter should provide better attenuation at higher frequencies, even into the GHz range. Even a simple first-order filter will continue to provide more attenuation as frequency increases (attenuation doubles as frequency doubles). Higher order filters will provide a sharper drop-off past the cutoff frequency, approaching an ideal filter as the order goes to infinity. However, filters are often designed with resonance around the cutoff point that causes the signal to be amplified around that frequency.

shadowman:

Can you explain that joke a little further?  I still don't get it... 

That's because you need to keep thinking of different possible meanings of the joke.  The one that makes sense will probably be the last one you think of.

 

A co-worker of mine once owned a computer repair shop. He had a customer bring in a totally unshielded monitor for repair. The funny thing with this particular monitor was that whenever it was turned on it generated a lot of EM interference. So much that it would disrupt the normal operation of electronics within a rather significant radius. Causing any TV or monitor to go haywire, and rendering cell-phones and radios useless. The effect was not as localized as you might think.

WhiskeyJack:

shadowman:

Can you explain that joke a little further?  I still don't get it... 

That's because you need to keep thinking of different possible meanings of the joke.  The one that makes sense will probably be the last one you think of.

 

I can't think of any.

shadowman:

Can you explain that joke a little further?  I still don't get it... 

Why would you keep trying things once you've found what works?  (Unless you're SpectateSwamp).

If you try things until they work, the one that works will be the last thing you try. 

belgariontheking:

shadowman:

Can you explain that joke a little further?  I still don't get it... 

Why would you keep trying things once you've found what works?  (Unless you're SpectateSwamp).

If you try things until they work, the one that works will be the last thing you try. 

 

Your sarcasm detector is just all sorts of broken today isn't it?

belgariontheking:

Why would you keep trying things once you've found what works?  (Unless you're SpectateSwamp).

If you try things until they work, the one that works will be the last thing you try.

Hmmm..  in my experience the thing that works is the first one my co-worker tries after I give up and ask for help.