For $29/mo, we provide access to advanced level technicians who will answer your questions on any Macbook board related matter to the best of their knowledge promptly & walk you through how to solve your problem so you can deliver a working board to your customer.
Inject voltage on the rail and see what heats up. Slowly go up in voltage and monitor current. At 2-3 amps something should get warm. Don't go over 12V of course!