Home-built EDM

I just completed construction of a home-built EDM from an article by
Arnold Gregrich in Home Shop Machinist (October/November 2002).
The initial test results were disappointing to say the least. Using
plain tap water, I could hardly get any sparking at all. When it did
spark, there didn't seem to be enough power to start a hole, much
less burn clean through a piece of 1/16" thick steel. I changed over
to deionized water with no real improvement. The sparks seem to
wander and not concentrate in one area.
These are the specs: Used two 3600 uf caps, a 400V rectifier and 200
watt light bulbs in both sockets. The electrodes I tried were .062"
mild steel welding rod, ¼" copper tubing and a piece of a telescoping
car antenna (chrome plated brass which didn't work at all).
If anyone is familiar with this machine, I sure could use some tips
on increasing performance. I need more aggressive sparking, but how
to achieve it is the question.
Rich