USB port problem, please help!

[sesselpupser]

So here's the thing:

Maybe two nights ago I was playing something and my mouse, a Logitech G500 which has always been plugged into the back of my PC, reset itself to the lowest sensitivity. I just turned it back up and thought nothing of it.

Last night, the mouse suddenly started acting as if the cord had broken inside the insulation, i.e. the power was intermittently turning on and off, I tried wiggling the cord around and it seemed to be having an effect so I decided to 'repair' the mouse without testing it in another computer. Because it's kind of hard to reach the back of my PC, I plugged it into my keyboard (an Apple wired aluminium keyboard with a tenkey) and it worked fine. I considered it a successful operation and plugged the mouse into the motherboard again, and the problem returned.

Uh oh.

So I tried it in one of the USB 3.0 ports beneath as all the other 2.0 ports were occupied, it didn't work. I tried it in one of the front panel ports and again, it didn't work. I tried switching my G27 (plugged in to the back) on, the power LED on it flickered like crazy and it kept calibrating, as you'd expect if the power was being intermittent.

Other devices plugged in to the back of my PC are my PS3 Eye camera, the power LED of which suggests there's nothing wrong, an iPhone cable that seems to be charging my phone just fine - the battery level hasn't gone up yet (but it's only been plugged in for about 20 seconds) but there's the lightning bolt icon next to the battery - and my keyboard which has worked fine for the entire period.

Devices plugged in to the front panel were my Dualshock 4, which I used in USB mode to play games last night, and my X52 Pro flight stick. The X52 is an interesting one; when plugged in to the left port, the LEDs illuminate as they should. When plugged in to the right port, which is where the Dualshock 4 was and it's also the port I tried my mouse in, the LEDs do not illuminate.

The weirdest part, as far as I'm concerned, is this: My mouse doesn't work when plugged directly into my motherboard, but if I plug it into my keyboard, which is plugged in to the USB port right next to the one my mouse was plugged in to, it works fine!


So is it possible that each USB port or groups of USB ports have power smoothing capacitors on the motherboard, and that some of mine may have gone bad? Or could it be a PSU problem? The thing is, there are no other signs of my PSU being bad at all; no blue screens, no odd sounds, everything seems fine. Should I make a 2.5W load out of resistors, hook up my oscilloscope and see what the supply ripple is like on each USB port, maybe? I'm kind of stumped and I could really do without having to buy a new motherboard, since I can't afford a new CPU to go with it right now and I don't want to buy a new old motherboard that'll have to be replaced when the CPU is due for an upgrade!

 

[Grayfox]

Normally each USB pair is controlled by the one controller so if one shorts out the other wont work.

But your mouse doesnt work in a USB 3 port when it is normally in a USB 2 port?

Then it seems your mouse or it's drivers are screwed.

You can get a USB PCI card or a USB hub

 

[sesselpupser]

Normally each USB pair is controlled by the one controller so if one shorts out the other wont work.

But your mouse doesnt work in a USB 3 port when it is normally in a USB 2 port?

Then it seems your mouse or it's drivers are screwed.

You can get a USB PCI card or a USB hub

I've tested it a bit further and found some odd results.

- The G500 works fine in the front left USB port (but not front right, front 3.0, rear 2.0 or rear 3.0) or any other USB port as long as it's plugged in to my keyboard.
- The Apple 'mighty' mouse works fine in either front USB port but not the front 3.0 or any of the rear ports.
- The X52 Pro seems to work fine in the front left port, the LCD backlight comes on and so do the LEDs. In the front right port, the LEDs come on but LCD backlight doesn't, in the front USB 3.0 port the LCD backlight comes on but the LEDs don't. In any of the rear ports the LCD itself flickers and the PC doesn't recognise the device.
- The G27 works in the front two ports but not the rear ports.
- The PS3 Eye works in any USB 2.0 port.
- The keyboard works in any USB 2.0 port, and the mouse works when plugged into it, even when the keyboard is plugged into a USB port that was causing the mouse to malfunction previously.
- The DualShock 4 works in any USB 2.0 port.

So I reckon it's a power smoothing problem and probably that my USB 3.0 ports just don't work at all. I can't think why else the mouse would not work when plugged into a specific port, but when you plug it into the keyboard then plug the keyboard into that same port, both keyboard and mouse work fine. The keyboard must have it's own smoothing caps, hence why the mouse works. That would make sense, right?

 

[BobK]

Should I make a 2.5W load out of resistors, hook up my oscilloscope and see what the supply ripple is like on each USB port, maybe?

That's the place where I would have started. Would probably have been quicker than the time it took to compose your OP, in fact.

In any case, sounds like power is very likely the culprit; hence checking with the 'scope. I would be shocked and amazed, though, if it's the PSU; if it were it should affect all the USB ports not just a few.

 

[sesselpupser]

That's the place where I would have started. Would probably have been quicker than the time it took to compose your OP, in fact.

In any case, sounds like power is very likely the culprit; hence checking with the 'scope. I would be shocked and amazed, though, if it's the PSU; if it were it should affect all the USB ports not just a few.

The only reason I haven't grabbed my scope just yet is because I'm lazy and I've lost my breadboard-friendly USB cable, oh and I don't have any 10R 2.5W resistors to hand, not sure I have enough 10R 0.25Ws to make an equivalent network that can handle the power, either. Also I kind of thought that even if it is supply ripple and I do see it on my scope, how does that help me fix the problem? I've looked at the motherboard and I can't see anything untoward, no bulging or leaking caps or anything and I can't work out the logical next step. Do I assume the motherboard is dead and replace it, or... What? How can I test the PSU to make sure that's not the problem? A whacking great array of high-power resistors to max out the 5V rail current supply?

But thanks, that backs up my theory that it's probably not the PSU. But, really, I think I'd prefer it if it were, a PSU is cheaper than a CPU and motherboard. Less exciting, though...

 

[BobK]

Given how severe the problem sounds, I would think you would need anywhere near half an amp of current draw to see what's happening; a half watt 47 ohm resistor should work. Or four of them.

The reason you'd want to use the scope is to try to localize the problem. Cracked/broken trace on the motherboard, cracked solder joint, etc, etc; whatever it is may not require a motherboard or PSU replacement. But unless you look you can't do anything more than guess. Besides, even if something does require replacement it's nice to have a positive indication of what to replace.

 

[sesselpupser]

Well, this is embarrassing, but... I restarted my PC and everything is fine now. That's even less exciting than replacing the PSU, but also much cheaper. I can't even imagine what caused that to happen, and I didn't even think to check because, well, it looked exactly like a hardware problem.