Are electro cap jackets insulated/insulated?

[mth5044]

Never really gave it though until now that the situation arises. Resistors seem pretty isolated - they can touch and be fine. What about the outside of electro caps? Box and greenies can touch, but they appear to be made out of some kind of plastic polymer. Electro's seem more metallic under their shrink wrap labels. I can't imagine parts that get stuffed into tiny places would not be insulated, but who knows.

The situation is that a laying down electro could connect two traces together using the outside as a bridge. Thanks!

Edit: Multimeter says nah, you're good. But it has lied to me before.

[R.G.]

The interior metal can is  common to one of the leads, generally the negative one in ordinary ones. Don't know about bipolar/non-polars. The outer plastic sleeve is intended to insulate the can to avoid shorts. I can't think of any electro cap I've ever seen with a conductive plastic outer sleeve.

Treat it as insulating until proven otherwise by some weird cap.

[Ice-9]

As far as I'm aware the aluminium outside can of electro's is usually not connected to any internals of the cap but I would never take that a total rule of thumb especially when dealing with high voltage caps in a PSU of a valve amp for example as it is always worth checking if in doubt.

If the outside can had the heatshrink tube removed and was touching the legs of other components then it would obviously cause a short across those components or tracks (but not within the cap).

[R.G.]

It may not be intentionally connected (it was at one time)  but the can is full of the electrolyte, and hence likely to conduct to one or the other place.

It is possible that modern caps have insulating insides on the cans and they don't conduct. I haven't checked recently. But from painful experience in the past, I always assume that the can is connected. If I'm wrong, then I've made it double safe. On the manufacturing front, it's easier to insulate the outside of the can than the inside.

Could be they do both inside and outside, I guess.

[PRR]

> I can't think of any electro cap I've ever seen with a conductive plastic outer sleeve.

But beware the bare metal chassis-mount cans used on older tube amps.

These were usually riveted to the chassis, therefore as safe as the chassis.

Particularly beware on high-voltage amps. Ampeg stacked two in series across 590V. The can of the "upper" cap was at 300V. They used a cardboard sleeve and phenolic mounting washer (which were available accessories in the day). It was nominally safe. It still scares me.

AFAIK, caps with leads at each end, the negative lead is welded to the can. And as R.G. says, one-end caps with rubber plugs still have the damp electrolyte directly against the can.

> Resistors seem pretty isolated - they can touch and be fine.

This I am much less sure of.

Carbon-comp is mostly clay and probably safe to touch other stuff.

Many film (and wire) resistors have metal ends with just a coat of paint. In distribution and installation, paint chips. Also if something goes wrong and the resistor gets very hot, the paint may pop-off. I think I have seen trouble like that. Me, I would not let resistors touch other stuff.

[mth5044]

Good info, thank you gentlemen.