I'm fairly new at this and self-taught, so assume I'm ignorant and my apologies for any incorrect terminology.
I'm repairing my 3D printer for the third time, and the previous 2 breakdowns and repairs, including my terrible soldering, have left the negative terminal for the power in really bad shape. (More details on that below, in case it's relevant) I'm wondering if I can just attach the negative wire for power to one of the other negative terminals on the board. With my very limited experience, it makes sense to me that all of the negative terminals would connect to each other, and it wouldn't really matter which I connected to. Is that true? This is a cheaply made and cheaply assembled board, so I can't guarantee that it complies with best practices, in case that matters.
More details on the situation: There was originally a power connector with screws to attach the wires, but the first breakdown (due to poor design) caused it to melt. I added a MOSFET board to fix the bad design (a common upgrade for cheap 3D printers) and soldered the power wires directly to the pins that were inside the melted connector. I did a bad job, and after a couple of years, one of the joints broke. I discovered that the pin had become quite lose, and I decided to try to re-solder it more securely. The pad seems to be totally gone, though, and the best I could manage still left it wobbly. I believe a combination of the breakdowns and my poor soldering has damaged the board a bit around the pin. I don't think I have the skills to repair it, and if attaching to another negative terminal will work, I would prefer to do that. If not, I'll attempt to repair the board, but that's probably beyond me.
Here's a guide to the MOSFET upgrade I did with some decent pictures of the board in question, in case that's helpful: https://thatnerdchannel.blogspot.com/2017/06/mosfet-upgrade-wanhao-duplicator-i3-v21.html
The reprap page on the board: https://reprap.org/wiki/Melzi
- Includes schematic and a decent picture of the full board
- My specific board appears to be the "eBay hybrid"
Side question: If I scratch off the outer layer of the PCB near the burnt negative terminal, am I right to think that I will hit the layer of copper the terminal connects to, and that I could attach to that? (I believe this is basically how repairing the board would work.)