Probably too late now, they probably kaput
The difference is that "old" Airtronics servos have their plugs wired with the pos. and neg. power leads reverse from all other servos, you have to switch the wires on the JR serovs so that the neg. wire is in the center of the plug and the red or orange plus wire is on the end of the plug facing the end of the receiver case. If you have already tried to power them up they are probably toast[:@] Sorry.
Pete