On the jig as long as you have 300Ohm across those two pins it should work, and you said it does put your phone in download mode, I believe it is right. Maybe Samsung changed something in the bootloader. I know there are some older ones available on the sprint section of the repository for our phone.
One last question, can you run it in recovery or download mode for a longer time without it being plugged into power? (go into recovery and just scroll through the options for a while not doing anything)