The hacker's paperclip.

On Slashdot, I found a comment giving little, good tips on how to solve annoying hardware problems with a paperclip.

The power supply tester
Creation: Unbend a paperclip, and then bend it into a big U shape.

Usage: When you are unsure whether a PSU works (a) disconnect it from anything it is connected to (b) insert one leg of the U into the hole in the 20/24 pin motherboard power plug for the green wire (c) insert the other leg into a hole for a black wire (d) plug the PSU into power and turn it on.
If the fans spin up, then the PSU at least partially works. At this point you can use a multimeter to verify the voltages of the different rails with no load.

The CD ejector
Creation: Straighten a thick-gauge (strong) paperclip, and then put a loop in one end that is big enough to put your index finger through, at least to the first knuckle (this helps with gripping it during use).

Usage: When you need to eject a CD from a powered-down computer (laptop OR desktop), push the paperclip into the emergency eject hole. On a laptop, this requires very little force, but on a standard (5.25") Desktop CD-ROM drive, this will take quite a bit of effort.

The multipurpose grabber
Creation: Straighten a regular paperclip, and put a loop on the end, as you did for the CD Ejector. On the other end, put a 90 degree bend, 2mm from the tip.

Usage: You can use this tool to remove or move jumpers (very handy for IDE hard drives), and to remove stuck floppy disks from floppy drives (use the R/W hole or 1.44MB hole as an anchor point).

Credit must be due to beav007.

Small Linux tip: Companion controllers and USB hardware

Browsing the Gentoo forums I stumbled on an odd problem with one of these "easy-but-who-the-hell-would-have-thought-of-this" nasty solutions.

Symptoms: You connect a USB hardware (e.g. an USB scanner) and nothing happens. It seems it is not recognized. But you know that your scanner/printer/whatever works and it should work with Linux! (This often happens with SiS motherboards)

Solution: Check you have OHCI/UHCI support enabled. If not, enable it. Try modprobe ohci-hcd and/or modprobe uhci-hcd as root. If even this doesn't work, chances are you compiled your kernel by yourself (most distros should include OHCI): check in your kernel config you have OHCI enabled.

Rationale: The problem is that a USB 2.0 controller card is often coupled to OHCI (or sometimes UHCI) controllers, to deal with low or full speed devices, while the EHCI controller keeps the high speed devices for himself. The hardware switches controllers depending on the attached device. So if you only have EHCI drivers and your scanner switches to the OHCI/UHCI controller, there won't be a driver for that controller -and therefore, your PC cannot communicate with what's attached there. You can read the full explanation here, look for "USB 1.1. "Companion Controllers"".