Thank you for the detailed insight! I miss some basics in electronics but am eager to learn how to test and fix circuits.

Years ago I tried to repair an old keyboard/synthesizer by cleaning it and replacing leaked/bloated capacitors. Unfortunately the onboard sound memory could not be loaded anymore or was wiped entirely as far as I understood. But due to lack of knowledge (me and community that time) it was too complex to got the keyboard up and running again. It's sometimes sad to loose good hardware...

Back to the resistor/thread: I can't imagine a resistor to be the source of the problem. Isn't it more possible that a capacitor wears out or a transistor cooling fails?

Isn't it safer/better to start by replacing and testing with a higher resistor? Or is my thinking too simple?