Bought some vintage electronics, and the 20 foot data cable bundle smells like mildew very strongly. I need something to seal in that smell and kill the fungi on the insulators, without damaging the not-easily-replaceable wires & cables.
I know this is an old Question, but several of the answer aren't good solutions.
Bleach can destroy the insulation. Isopropyl alcohol won't kill the mold. Baking soda may kill the mold as a dry powder, but will still have to be washed off or you'll leave a trail of white dust behind. Even after it's washed off, it might still leave a white residue.
The best way I've found to kill mold while not damaging anything else is to use hydrogen peroxide. Some molds will go into a "hibernation" style cycle when it comes into contact with too much bleach, so it'll survive and eventually come back. Hydrogen peroxide reacts to mold like it does to blood, it bubbles up because the extra oxygen atom is bonding to another oxygen in the organic bits of mold. The reaction ends up being water and gaseous oxygen, plus whatever is left over of the mold, which definitely won't survive.
Put enough H2O2 on so that it bubbles, and when it stops bubbling, add more until it no longer bubbles with the new application. If the cable isn't brittle, you can try scrubbing off any obvious mold spots. Then you can rinse it down with regular water and dry it off. Since the smell is due to the spores, you shouldn't have any more bad aromas.
Baking soda is quite good at removing odors. "Mix" the cable with baking soda, put everything in a sealed bag. Excess soda will not hurt, add more to the bag.
Occasionally mildly shake the bag with the cable, to allow "fresh" soda to work on the cable.
Note: it might work better if you prepare a very concentrated baking soda solution (with water). However, the water may infiltrate internally (the cables being old) and as a result do more damage than help.
I used that trick with winter boots, even without the bag. All odors disappeared quickly (less than a few days).
If removing the odor from the cable does not work, you may want to remove the cable entirely, and replace it. You might even be able to find a similar cable, to keep the vintage look of the thingy.
Try a dilute solution of chlorine bleach in water.
When we first bought our house, there was black mold about 18" up from the floor on the drywall in the basement. I sprayed that with a 10% solution of Clorox®. In little time the black disappeared, and so did the moldy odor.
Remember to use rubber gloves, keep it away from the contacts, and clean it off thoroughly afterwards.
If it is gooey and sticky, you can use an alcohol based product to clean and remove all the dirt on the wires. Acetone is abrasive, so I use isopropyl alcohol (IPA) instead. It cleans surfaces very well and is not abrasive or discoloring, I think it will also get rid of the smells.
Febreeze Fabric or Febreeze Fabric Extra Strength can seal-in all sorts of odours…
without leaving behind any tell-tale artificial bouquet stink.
Some people (me) are sensitive to the various scents added to the stuff; but, the fragrance-free, unscented stuff seems acceptably undetectable. If the scent or effect of the specific recommendation is suspect, I encourage you to test it on something expendable before you put it on anything of value.
The stuff works by encapsulating the offensive odour within a thin non-porous vapour barrier. It's applied from a pump-spray container and when applied according to instructions works as advertised. It covers every nook and cranny as it was made for covering household surfaces from upholstery to carpeting including whatever was on, or in, it.
Applying it is rather simple. Spread the data cable bundle out in a loose coil on the floor or some suitable spot. Mist the bundle very lightly, wait a few seconds, flip the bundle over to do the other side. A couple of very light applications with a brief drying-time between is more effective than a single heavy application. That should swallow any similar odour I can think of.
Another benefit is that it does not affect electric or electronic connections in any way when dry that I'm aware.
Jeweler's wash, which you use in sonic jewel cleaners. Allow the ends to soak in the wash for 1/4 hour. The stuff is super and can be used on metals as soft as gold.