Here is an interesting snippet.
From
http://www.sae.org/aeromag/features/spacestation/ interesting bit below.
Diagnostic tools will be primarily used to perform fault isolation. Crew members will remove a defective ORU, carry it to the MWA, open it up, and use the diagnostic equipment to pinpoint the faulty component. Once identified, the component will be replaced, and the diagnostic equipment is again used to determine if the repair was successful. For situations in which the ORU cannot be removed, the diagnostic tools can be carried to the unit for maintenance.
EVAs are performed outside the station using special tools, tethers, and aids.
One such diagnostic tool is a scopemeter, which is a combination of a multimeter and oscilloscope manufactured by the Fluke Co. It can be used to measure voltage, current, and resistance to detect, digitize, store, and display waveforms with frequencies up to 100 MHz. Using special probes, it can also measure temperature and pressure. The scopemeter features a liquid crystal display and is powered by a rechargeable power pack. This tool was shipped to ISS during flight 2R in October 2000. Another one will be sent up on assembly flight 6A in April.
Another piece of equipment to be hauled on flight 6A is a pin kit, which is housed in a Nomex pouch and has some of the same components as the one used by the Space Shuttle crew. Items unique to the ISS pin kit include prefabricated jumper/test cables, materials for manufacturing custom jumper cables, alligator clips, and assorted fuses.
ISS crews also use a logic analyzer, which consists of a portable computer, a portable computer memory card international adapter (PCMCIA), and LabVIEW software. The PCMCIA card has numerous probes to allow the computer to monitor several different points in a circuit or several circuits simultaneously. The logic analyzer application software is designed to monitor the logical state ("1" or "0"; high or low, etc.) of particular points within a circuit or electronic component.
A function/sweep generator produces standard waveforms - sine, saw-tooth, and square - to diagnose electronic circuits and perform fault isolation. Generally, this tool is used to inject a known reference signal (wave) into a circuit; the output of the circuit is monitored with the scopemeter or the logic analyzer. The function/sweep generator used onboard the ISS is an off-the-shelf unit that has been repackaged in a new cabinet and adapted to operate from 120 V dc power.
A power strip is also employed. It plugs into a standard UOP and provides four UOP type sockets, each of which can be switched on and off independently. The four sockets can be used to provide data connections. The unit also features a removable fuse.