Sentinel (Again)

[Normski-MRN]

I want to wire (a fully working) Sentinel 30/35 box into my winipac switch. No before doing this I want to check I have go it working off +12v and ground the Parallel Interface shows:
Pin 1 - COM A
Pin 2 - A.1
Pin 3 - NC
Pin 4 - A.2
Pin 5 - A.3
Pin 6 - Select
Pin 7 - A.4
Pin 8 - I.4
Pin 9 - 12v
Pin 10 - 0V
Pin 11 - I.3
Pin 12 - I.2
Pin 13 - I.1
Pin 14 I.5,6
Pin 14 I.7,8

Now I have wired Pin 9 to 12v and Pin 10 to 0v (GND) and Pin 1 to 12v
If I do this all coins reject.

If I disconnect Pin 1, the first coin accepts and further coins are rejected.

Question: How do I wire Pin 1

[lanman31337]

I think that would go to the ground (or common) on your ipac.