Vintage Simmons Drums (UK) Users Group

I have a full set of Simmons Pads. circa 1982 (?)

I am trying to use them a practice pads w/ an  Alesis D-5. Most od the
chords needed to plug into the pads, well, all except 1, are cannon
with 1 exception of an instrument chord. I can not get much attack or
signal to the Alesis in order to hear the pads. What am I doing wrong.
If it is the chords, where do I get the proper chords?