[Device Repair] R7027:
For reference, my previous reply to you is here:

https://xdaforums.com/t/how-to-check-voltage-level-at-a-resistor.4517797/post-87806941

What do you mean by superficial repair? What made you suspect the charging cable?

Kaput? I know that word. That's a German word for broken. I wonder if he told you this because he wanted to repair the components on the board, or because he wanted to toss out the old board and install a new board and call it repaired.

So you already tested with a new battery. Good! That's one of the first things I would do as well. GSM Arena says the battery is "Li-Ion 2100 mAh, removable". At least you didn't need to send it in or leave it to a repair shop to replace the battery. I remember the time when you could replace the battery of your phone yourself. That in itself was very satisfactory. Those were great times! Those times are gone. Now you have to pay a premium to replace a battery. It's "complicated" they say, and so it's not for everyone (or anyone).

Hotter than what's usual for a phone that's charging? If it's shorted, charging may damage it further. You can test it of course, but you're risking it. Don't test charge for longer than you need to, preferably not at all as soon as you realize there's something wrong with the device. There's the risk of battery leaking or catching fire. So be careful and don't leave it unsupervised.

What kind of tutorials are you reading or watching? What do you think is the problem?

You have to go over more than a few tutorials if you want to be able to intuitively know what to look for or what to do. One way is to start learning about electronics in general, experiment and learn, before you get down to this specific problem. Another way is to start exploring from the repair side of things and work your way into the topic of electronics repair by troubleshooting this specific problem.

Your problem is most likely caused by a short somewhere on the board. So I would suggest you learn about short circuits or "shorts" for short (duh) and how to find shorts in general, and then work your way down to how to find shorts on mobile phones specifically.

I know that feeling. I'm wired the same way. If I can, I will try to repair and fix things on my own. Sometimes I will take on things I hardly know anything about. I will try anyway and learn in the process. Some things are admittedly more difficult than others. But that's how you learn and grow your knowledge base.

People no longer repair things. They throw out the old and broken things, and just keep on buying new things like on conveyor belt. This is not good in by any means. The biggest negative impact of this I think is that people stop using their head. They begin to believe that everything in the world is automatic. A light bulb is the result of true magic, especially when you throw in smart home plugs and switches into the equation. People are slowly being turned into slaves of consumerism. Common knowledge diminishes, like what household products you can use to remove stains, and we only live to serve a higher purpose of capitalism.

Do you have the service manual for this phone? You can usually find these online free of charge. Do you have a multimeter? The first tool you should buy and learn to use is a multimeter. Learn about the continuity test, diode mode, and how to measure voltage.

I worked as an electrician and I felt like I had to ask about how to measure voltage at a resistor, because I was unsure and didn't want to risk damaging a board more than it already is. As an electrician, I worked with voltages relative to Earth ground. I never worked with electronics, although I did get basic electronics training and I know all the basic components and how they work. We worked with soldering iron as well, and learned to use an oscilloscope. I was best in class at soldering. This was a long time ago though. We programmed PLCs, made Delta and Y-configuration connections of three phase electric motors, worked with relays and contactors, and we learned a whole load of other useful things.

My point is, always ask someone more knowledgeable and experienced if you're in doubt about something, rather than taking a risk or gambling. This is much more important of course when working with unforgiving high voltages and high currents, so as an electrician I learned early on to respect electricity. This was all part of my training and thankfully I have never had any accident. It's OK to make mistakes, and you're bound to make mistakes when experimenting, but you better have a backup plan and put in some kind of safety net, to protect yourself and to protect your equipment or whatever it is you're working on.