Way to diagnose if logic board power cable is loose or disconnected?

Hi everyone,

I needed to replace the logic board on my ancient Macbook Pro A1260 (I diagnosed that need through careful reads of descriptions of symptoms and diagnoses on iFixit). I knew the repair would be risky because of the difficulty level (i'm totally new), but decided to go for it, order a replacement logic board from iFixit and replace the old one. I dissassembled and reassembled my machine carefully following iFixit's excellent guide for replacing the logic board. But upon reassembly the machine did not power on at all. No start up noises whatsoever. I think I have two possibilities about why this might be:

1) Possibly the logic board power cable did not get properly reconnected at Step 21 of the guide during reassembly. My question: Is there a way to diagnose whether the logic board power cable may be loose/disconnected without having to fully disassemble the machine down to Step 21 of the guide? If possible I would love to avoid the full disassembly route to diagnosis because of the 8 delicate connectors that must be disconnected at Step 14.

2) Speaking of Step 14: during reassembly at Step 14 I managed to reconnect all 8 connectors, but one was damaged in the process. It is the tiny two pin connector at the top left corner of the logic board near the left fan (when the machine is facing me as if I were typing on the keyboard). I did get this connector properly seated on the logic board, but not before both male pins broke (on the connector, not the board). Could this broken connector be the cause of the no power up situation?

Anyway, I'm completely new at this (as you can probably tell) and understand I was getting into a difficult repair. If I'm outta luck ... oh well... at least I learned a ton in the process. Thanks for any suggestions...