MBP Retina A1502 Logic Board DEAD

Angelo, this is not an answer to your specific question but it is 'free' advice I am offering you (suitable for framing or wrapping fish :>); please don't take offense. You have mentioned on this and other forums that you would be willing to pay for remote help/teaching, that you have good micro-soldering skills but less so on understanding schematics.

Remote teaching and troubleshooting is very difficult and requires that both parties speak the same language. I am not talking about English/Portuguese but the language of electronics. I believe this is where you need to focus your short term efforts. If you don't understand what a capacitor or inductor or transistor/MOSFET is, how they work and how to test them, then you will always struggle to understand a schematic and troubleshooting will be difficult.

If you are going to be doing board level repairs as a business, I think you should be investing time and effort to understand at least the basics of electronics. You don't need to be an engineer! Once you understand what a component does and how it behaves, you will know how to test it and whether or not it can be shorted or removed.

This is a good tutorial on how engineers deliver clean power to IC's. This is very relevant as the majority of the capacitors on an iDevice/Mac logic board are there for this specific reason. There are several articles in the series and they touch on capacitors and ferrite beads (filters). Another good source of materials is ElectronicTutorials. There are also some good youtube channels such as Afrotechmods, AddOhms and of course the EEVBlog.

Invest in your business and in your skills and it will pay itself back! In the future, when someone suggests you check a voltage rail or filter, you will know what to look for and how to test it. Schematics will start making sense and pretty soon, you will be the one answering logic board questions on iFixit!!