How do I pass level 6 in chapter 4?

I've figured out how to get past the first door, but once I get in I don't have any power sources with me to open the next one. I've tried re-arranging things at the first door over and over again, but every configuration that works requires all available power sources. What am I missing?

Spoiler-light hint:

Look for residual power in one of the wires after a power source shuts off.

Spoilerific walk-through:

First, arrange the power orbs correctly so that the first door stays open.
From top to bottom: Green, Purple, Blue.

Next, get as close as you can to the first door while still being in range to pull out the power orbs.
When the green orb turns on, quickly grab the purple one and go through the door.
There should be just enough charge left in the wire for you to get through before the door closes.

Use the purple orb to progress through the next door.