Ballast/wiring issues, PLEASE HELP

Ok, so I'm running a Growbright 600w HPS ballast, and it uses the 277/240/208/120 wiring diagram, w/ a 7-cable plastic harness. My problem is that the plastic harness was very poorly constructed, and as such would not let me loosen the screws to appropriately secure/fasten the fixture wires going into the first two spots. The white cable melted the far end of the wiring harness, and now that last port isn't usable. Do I have to buy a whole new light setup, is there a way to replace the harness, or would it be terribly dangerous to just fuse the two wires together outside of the wiring harness and seal it w/ some electrical tape? I'm trying to figure out what is the safest, but most economical solution. Any assistance would be appreciated. Thanks!

Cut wires, join, solder, wrap with electrical tape 3 layers thick.

Best I can do to help you, besides saying just buy a unit dedicated for your power source (and not universal) so you don't have to futz around with the inevitable wiring harness problems.