Discharge capacitors before fucking with them.

Any bubbled up and leaking condenser may be acidic, don't touch it.

Soldering fumes are bad.

That's all I can think of.

Mostly I just work in a well ventilated area. Oh and for sure disconnect power before desoldering anything.

Other than that, I avoid taking apart microwaves (beryllium, high voltage), anything with a CRT (imploding glass, high voltage), and high voltage transformers (transformer oil, high voltage). Also any medical equipment (chemical hazard, radiation hazards, biohazard, high voltage, imploding glass). Oh and no unexploded munitions for reasons that should be obvious (people still salvage these in my country and it sometimes doesn't end well).

I find a hot air rework station+tweezers a much faster way to salvage than jamming a hot iron into boards. Also lets you salvage SMT components, which are most of the better parts these days. For 1970s stuff, it's mostly through-hole, I'd test the parts before trying to reuse them. Capacitors especially. Got to love those big transistors from our side of the Iron Curtain though.

Some old electronics use asbestos in heating elements or for shielding. Be careful when dealing with old hair dryers, coffee makers, stoves etc.

I don't see how there could be any in your tape recorder though. It's just what came to my mind when I read the title.

There is the old thermal paste made of Beryllium oxide. Best not to eat it.

Wear trainers not sling backs. Molten solder and your tootsie don't go well together.
I turn the printed circuit board component side down and wave a hot air gun over the flip side, whilst tapping the board against the edge of work bench. The result is usually a cascade of components (and blobs of molten solder).

Very therapeutic. When I'm stuck trying to work out how to do something, when everything I have tried has failed miserably, I deconstruct something electronic. No, I keep well away from psychiatrists.

You (I anticipate) won't be doing this 9 hours a day, 7 days a week - most of the nasties are long term exposure ones, so a one-off should be fine. If anything ever irritates your eyes or throat, get out of there and ventilate the place.

• luminous dials can be radium paint.
• White paint is often lead and very poisonous to eat - wash hands
• asbestos insulated wires, resistor cores and more - look for crumbly "cement" or woven fabric: https://www.asbestos.com/...

I'm sure you will not breath in any dust and will wash your hands so you will likely be fine. This is most likely an issue if you mod the case with drilling/filling or are a little careless.

Don't lick anything. Don't eat or drink on your workbench.