I'm an electrical engineer. Even though I'm working with embedded software, I'm sorrounded with hardware engineers. We found the schematic of the 502, which is similar. After that, it still took us a few hours to investigate the layout and find where it's connected
You can remove the microphone from the main mix by unplugging it :) Microphone is only wired to the main mix, if you want to remove that connection, you loose the microphone. And I don't think it's possible without modifications to disconnect the main mix from the phones.
Hey ! First of all thank you so much for this tutorial I've been searching for a long time and it's really good !
So, I have 2 questions to ask you:
(Sorry for my bad english i'm french 😄)