Oh, that's just a bit of anhydrous 1,3,4-difluoromethoxybenzyltriphenylmethylenglycolaldehydecarbamate; there is a class action lawsuit currently pending, and if you have been diagnosed with lung cancer, emphysema, osteoporosis, posttraumatic stress disorder, erectile dysfunction, glaucoma, or rectal prolapse you need to contact a lawyer ASAP (daytime TV is a good referral source) in order to ensure that you get the fair share of the settlement you are entitled to.

More seriously, some of that sharp, "hot" odor in a lot of old electronics is from phenolic circuit boards/terminal strips/insulators outgassing due to being heated (smells distinctive, but is nasty stuff and mostly banned in modern electronics in favor of fiberglass and other materials which are less toxic and less environmentally disruptive). There were also a lot of terminal strips/boards/insulators made of a laminated paper/resin material which also has a funky odor when heated. Otherwise, much of the smell originates from negative ions due to arcing contacts, accumulated dust/environmental fallout, mouse/insect feces/urine, outgassing varnishes on cloth-insulated wiring, and outgassing from the enamels on "magnet wire" in coils, transformers, etc.

Of note, there are a few pins which featured selenium rectifiers; if one of those experiences catastrophic failure and overheats, copious amounts of smoke containing selenium dioxide will result, which is a significant respiratory toxin (and produces the worst smell you will probably ever encounter, like a combination of burnt garlic + rotten eggs + dead fish).