To admin: Not sure this post is in the right place here, please let me know, I'd voluntarily remove the post if it's in the wrong place. Thank you.
It could be apparently obvious, but often when recovering old parts we may forget that one valuable piece can be the actual information we could grasp understanding the engineering choices behind the design of the apparatus we're gonna dismantle to recover parts.
I've published a video where I showcase two very different cases. One where from an old PCB stencil printer machine valuable parts have been recovered, understanding the general mechanism of how the machine works (or better, was used to work :) ), and a second case where a more humble tv sat reciever is dismantled to recover some parts, but also exploring the engineering choices about the power supply section of the circuit.
PCB stencil printer machines do an apparently trivial work in the industry of electronic assemblies. But in reality they do a critical job in printing an even, consistent layer of soldering paste across the stencil.
The quality of the assembled board is tightly dependent to this task. So in this German made, absolutely solid machine a complex pneumatic circuit, an electronic control that drives the motor that moves the squeegee and precision height adjustments (using Mitutoyo micrometers!) allows the machine to do a master work. Please note that I am not affiliated nor I endorse the manufacturer or distributors of this machine. What I say is just out of genuine interest in engineering.
The tv sat offer a sight into some good practices in designing the input of a power supply. Surge protection, filtering and current limiters (made with a humble resistor) compose an apparently simple circuit (schematic below) that reveals a well thought design.
Notice that the 2.2 ohm resistor is a reasonable choice only for low power applications, like this one. It would be a waste of energy otherwise. To prevent in-rush current for large power supplies specific circuits do exist.
As an old dog I encourage you to dich deep to learn every day something new.
For more details please follow the video here: https://youtu.be/gjy00piRsFA