the wiring is progressing slowly but surely, some more questions have popped up:
first, here are the schematics again:

as you can see, there's a GND wire running from the COU Edge Connector (blue, letter B) towards the Control Panel Connector. However, on its "journey to the Control Panel Connector" it splits up: one wire connects to the Control Panel Connector (blue, number 1), the other one connects to the Coin Door Connector (blue, number 6).
What is the function of that second wire running to the Coin Door Connector?let's continue: coming from the Coin Door Connector is another GND wire (turquoise, number 20) which end in this fork-like connector (crossed out on the schematics). This one has to be connected to the power transformator if i'm correct. Right?
the original pleiads wiring i'm using has a 24 pin amp coin door connector (NOT a molex connector). i'm removing this connector from the cab, because there are some wires attached to it which i'm not planning on using: -5V (number 19), +5V (number 14), coin counter (number 13).
the coin door wiring that's already in the cab looks like this:

as you can see on that picture, there are two wires coming from the microswitches: a purple one which registers the coins and a black one which should be a GND wire.
let me sum this up. there are several wires not connected yet: a ground wire from the transformator running to the coin door connector, a ground wire running from the control panel to the coin door connector, a black wire coming from the microswitches going WHERE???
now on to my questions:
(1) where do i connect the blue wire to which is running from the control panel to the coin door?
(2) where do i connect the turquoise wire to which is coming from the coin door and which ends in the fork-like connector?
(3) where do i connect the black wire to which is coming from the microswitches?
hopefully, someone out there is not as confused as i am and is able to help me out with my wiring problem!!! i'm almost done with it and can't wait to turn the machine on ...