You want high-tech? Maybe its just my background as an electronics tech, but I have used a dual-trace portable oscilloscope (Fluke ScopeMeter) to track down elusive intermittents.
By connecting between neutral and the 2 hot phases at the panel, and watching the relative amplitude of the 2 phases, one can determine whether the problem is a loose neutral at the service drop (one phase goes high, one goes low), a loose backwired receptacle connection (affected phase increases slightly as connection arcs-other phase unaffected), or a bad connection in the meter socket/disco/main breaker (one phase drops, other phase unaffected). By connecting the scope to the branch breakers, bad breakers and burned panel busbars can be found. A current probe is a neat accessory, but not a must-have. To help find the fault, turn on all the lights you can, and plug heavy loads into a few affected receptacles (I use a couple of 1000W halogen photographic lamps).
A combination of the scope AND a helper with a rubber mallet (looks better than a fist
) can help track down those nasty intermittents.
A suitable scope can be found nowadays for a few hundred dollars. Wide bandwidth is not needed, but complete line isolation (battery power) is essential for safety. 10:1 probes (rated for line voltage) are a good idea.
A scope and current probe is also nice for troubleshooting neutral overheating/harmonic current problems, or looking for radio interference from cheap dimmers/X10 modules/photocells/etc.
[This message has been edited by NJwirenut (edited 10-17-2001).]