Unfortunately with the ps2 controllers, only a few games like the Soul Caliburs support them, nothing can be done for Tekken 4 since it is simply not in the code.
The test switch is the first Dip switch, just switch it to on and that will get you into test mode, no need for anything on the harness.
Just wondering, why are you using converters? If 246 is set to 31hkz mode, it will display in 640X480 on any HDTV that supports 480p and most computer monitors (most 246 game manuals you can find in pdf will have the dip switch modes)