Quoted from PinMonk:
I would next power off and remove ALL (as in every single one, no shortcuts) of the 154 highlighted bulbs at once, then reconnect CN15 and reboot. Is the error still gone? If it's gone, then one of those bulbs is bad and you'll need to power off, insert a bulb, power on, check, repeat until you find which bulb (or bulbs, it can be two or more, don't get complacent and not test them all) is the bad one. If it's down to testing bulbs, I would just make the easiest socket of the nine 154 sockets to get to your "test" socket and run all 9 bulbs through it one at a time (power off, bulb in, power on, check, power off, remove bulb, repeat).
If taking all the bulbs out and plugging in CN15 you have the error still, then it's one of the nine 154 sockets that has a physical short. They'll all need to be inspected top and bottom. Probably a broken spring, but since you were in there messing with mods before this happened, you may have moved something and made a short outside the socket, so hard to say.
But let's not worry about the socket short scenario until you confirm that it's none of the bulbs by removing all the 154 bulbs and testing.
CN 15 connectors for your Node board are included in this manual last page 6, giving voltages. Looks like everything is 6V G1 through G3 on the CN15 connector, 3 power supplies. I think on the other manual page 46 you were referencing they want you to check CN15 terminal 1 to ground to see if you have 5 to 6 VDC source voltage 1st. I am assuming if you have that then you have a bad bulb or socket like some of the others were mentioning. Maybe check around the area where the MOD was plugged in to give you lights at the top of the towers, which would be my first thought.
Here is a link to all Spike boards, there are 17 of them but pretty sure the one above is the one to work off of since it is the part number for the Node 9 board. You have to scroll to the bottom of the page to see all the links (Red Boxes)