Get an Arduino kit, and start playing around with series/parallel circuits driving LEDs, using coils and capacitors, etc.
Really old stuff, with vacuum tubes, can have a "hot chassis" with mains voltage on it, and/or 200-300 volts on the plates of the tubes, be careful. Tube testers can be had, and so can tubes, for the most part.
Newer stuff, with transistors, usually has dead electrolytic capacitors that need to be replaced, and sometimes there will be other issues, most of the time it's a matter of tracing signals through a system to see which stage is at fault.
When you get to the newer stuff, with surface mount components, you'll need to have schematics and block diagrams in order to even start to figure out what's going on. The really new stuff has transistors and other passive parts so small you'll have to have a microscope to work on them with. You'll need hot air reworking gear to repair that type of stuff.
But first.... as I said earlier, start with the basics... programmers don't have good intuition about parallel and series circuits, etc. You can get multimeters and oscilloscopes very cheap these days.
If you want to get into radio, investing and playing with an RTL-SDR dongle and GNU Radio is a great way to get a feel for how things work, and to learn about negative frequencies, and all things signal processing related.
It's easy.... imagine a motor spinning at 10 turns / second... then reversing... it's now turning -10 turns/second.
When you have I and Q (Information and Quadrature of it), you can tell which way a signal is "spinning"... and there are many things you can't do if you don't have both parts of the signal.
If you have two antenna near each other, you can look at the phase and tell where the signal is coming from, in terms of which is closer to the source, by that rotation direction.
Really old stuff, with vacuum tubes, can have a "hot chassis" with mains voltage on it, and/or 200-300 volts on the plates of the tubes, be careful. Tube testers can be had, and so can tubes, for the most part.
Newer stuff, with transistors, usually has dead electrolytic capacitors that need to be replaced, and sometimes there will be other issues, most of the time it's a matter of tracing signals through a system to see which stage is at fault.
When you get to the newer stuff, with surface mount components, you'll need to have schematics and block diagrams in order to even start to figure out what's going on. The really new stuff has transistors and other passive parts so small you'll have to have a microscope to work on them with. You'll need hot air reworking gear to repair that type of stuff.
But first.... as I said earlier, start with the basics... programmers don't have good intuition about parallel and series circuits, etc. You can get multimeters and oscilloscopes very cheap these days.
If you want to get into radio, investing and playing with an RTL-SDR dongle and GNU Radio is a great way to get a feel for how things work, and to learn about negative frequencies, and all things signal processing related.