Taking apart old electronics

The most valuable thing you can get from discarded electronics is understanding. Try fixing them, or at least trace out the circuit until you can discover what is wrong.

It used to be very hard to get schematics, but now we have the Internet. Sites like http://eserviceinfo.com and http://ko4bb.com/ have service manuals for a variety of equipment. Even if you can't find the manufacturer's service manual, you can often find datasheets for the important components. Many designs don't stray too far from the datasheet example circuits.

Of course, you can learn about circuits from just reading datasheets and textbooks, but having the physical circuit in front of you gives another level of understanding.

You'll be paying youself only pennies per hour. I wouldn't bother with basic and cheap stuff like resistors and capacitors. ICs are often hard to identify, and old ones have little value today.

I would look for things like power transformers, speakers, heat sinks, relays, solenoids, motors, and large mechanical parts. Those cost more and are often hard to find. Sometimes just the box and chassis are the more valuable parts.

These days, there isn't much to get from consumer products. Look for reusable sub-assemblies rather than discrete components. For instance, laser printers yield nice high voltage supplies. Printers in general can be good for a motor or two, though good luck finding any specs on them. Sometimes you can get a display suitable for re-purposing from a dead laptop, but again, specs are the problem. Figuring out how to use something from just looking at the end of a ribbon cable and a power connector can be daunting.

Of course, if you're pulling apart old electronics, that's a different story. If it has vacuum tubes in it, while you may not personally have a use for them, there are people out there who would be happy to have even used tubes. The sockets for same are getting harder to come by as well, as are step-up transformers that supplied the voltages needed. If you encounter nixie tubes, just google them before you consign them to the trash can, you'd be surprised.

The best thing I've pulled apart in the last 10 years was actually a treadmill. It yielded a whole bunch of nice 7-segment displays, a power supply for the logic board, a great big DC motor, and a speed controller for same. Also, microwave ovens sometimes give up beastly large transformers - but be exceedingly careful with those, they can easily kill a person.