I'm learning electronics and I have an old C64 power supply which was made at our local electrical shop back in the 80s. I'm taking a look at it to try and understand how it works.
What I don't understand is why the DC ground is connected to mains earth. From what I gather this is to give a ground reference to the DC side but why would you do that?
Also the power LED anode is connected to +5V output on the 7805 and the cathode to the metal chassis. I can see how this works but does this mean current albeit small is flowing through the chassis to get to the regulator's GND?
Finally I would like to probe this with an oscilloscope to measure the ripple at various stages of the circuit. My assumption is that as all grounds are connected there's no problem probing anywhere on the low voltage side. Would I just put the probe crocodile clip on the chassis ground point?