And it's really simple.
STEP 1
Pull out the plug from ST1 on the 155
(Keep cable cause it can still be used as buscable if you ever loose or destroy one)
But for now, aside with it.
ST1 wil NO LONGER BE USED
STEP 2
Next to the plug you just remove sits a second, it's twisted and sits on ST2 next to ST1
Pull out the plug and fold aside for a moment.
THIS WILL CONNECT LATER TO CABLE B plug 1 (B1) in step 4
STEP 3
Look at the 154 and notice there are 3 cables
cable one is the buspower, it has the 18pole plug at it's end, at this moment not yet needed.
Cable 2 is called A
Plug this cable onto ST2 this is the connector on that led board that is NOT on the edge
AGAIN: st1 at the edge REMAINS EMPTY
Red stripe goes down, closest to the edge of the board
STEP4
From the 154 comes a longer cable with 2 connectors pressed to it. They call it B
Both connectors are protected agains shorts with a blind connector.
Manual say you should use the connector at the end called B1
Remove the blind connector from B1, leave the pins in.
Okay? Got it?
Now you should have connector B1 in your hand (yes the one at the end)
At step 2 I asked you to fold away the cable you removed from ST2
LOOK CLOSELY AT THE RED STRIPES and plug the cables together,
My cable from the 154 has not a massive colored stripe but is more some kind of red stipled line
Whatever:
RED GOES TO RED
Remark:
Cable B has two connectors
The second one is ment for your second A-155
You may however swap B1 with B2 if that suits your cable management better
These 2 are 100% the same, it can't go wrong here.