About 40 years ago, I sold my National NC-33 receiver to my friend G. He used the radio for a while and then sold it to a person, who should remain nameless. When I asked G. how his customer was enjoying the radio, he told me that he wasn’t. The buyer decided he wanted to upgrade the internal appearance of this perfectly functioning piece of equipment. To this end, he removed every resistor, thinking that all resistors were of exactly the same function and rating. This in spite of the obvious physical differences, including color code and size. He also did not bother to record where each resistor was removed from.
Something this stupid doesn’t happen often but people do often stop by Leeds with a big list of parts they want to buy to replace virtually every passive component, hoping that this will fix their non-functioning piece of gear. I have two important things to tell you about that. First: Replacing all the components is not troubleshooting. It’s stupid. People who want to do this have absolutely no idea how anything works. Secondly, replacing all the components increases the possibility of collateral damage. Vintage gear can be fragile and component removal in hard-wired chassis is difficult. The leads may have two or more wraps around the terminals they are on. Removing the solder and then unwrapping the leads while they still may be partially attached takes skill and patience.
Want to fix something electronic?
Baby step: Learn to read schematics. Learn every single symbol for every single component of the gear you are working on.
If you can’t do this go back to texting your friends or watch some cartoons.
Next step: Understand the circuit. It’s best if you start off knowing what every single component does. If that’s not possible you have to at least know exactly how each block works and what it does. If you can’t do this, you have very little chance of fixing the device.
Next: Unless you are really familar with the piece you need documentation. Schematic, manual, voltage chart, etc. Don’t have those and you’re not familiar with the piece of equipment? Then you have very little chance of fixing the device.
Next: Fix the most obvious problems: burnt resistors, missing parts, damaged parts, and any safety-related issue. Also check that it has the correct fuse. You can then power it up and make some measurements. Unfortunately this means you still need knowledge and experience, especially if you don’t have documentation.
Next: You powered the thing up and it still doesn’t work? You better have a scope. Don’t have one? Unless the thing is simple, it’s not going to be easy. If it is simple a DVM can work. And whatever piece of test equipment you use, you better know how to use it.
To learn all this takes time and patience. It’s the arrogance of the internet age that makes people think that they can do something without learning it first. I was once at a breakfast buffet where the chef at the omelette station could make two perfect omelettes, in two different pans at the same time. It was a ballet. I thought to myself that if I made two omelettes at a time every day for the next ten years that I couldn’t do that as well as he did. Nothing that matters is easy to learn. When you see people that make it look easy it’s because they are enjoying learning. Their gray matter, their motor skills, or strength is still working hard.