If you have electronic equipment from the 80s and 90s, please take a moment to learn about RIFA capacitors. This is one. They are often used in power supplies, and they like to make smoke, or start fires. See the little cracks?

They were poorly designed, and over time they develop cracks, which allows moisture in, which makes them fail. They all do; the question is not if, but when.

The dangerous part is that they are often connected such that they are energized EVEN IF THE DEVICE IS TURNED OFF. They start their little fireworks whenever they feel like it. If you do nothing else, please unplug old equipment when not in use.

Here's one that failed. It made a lot of very toxic smelling smoke. I was quick to unplug the device and leave. You don't want to breathe this stuff. Please read up on the issue, it has been widely documented. You must replace these.