Respecting foil capacitor 'polarity' in the restoration of vintage electronics gear is a much-debated topic these days. Some say it's crucial, while others say that it makes no difference as modern capacitors don't have the same issues as those of old.

While I personally am a little on the fence on the subject, I always do a test to determine which lead is connected to the capacitor's outer foil. Can't hurt, right? The oscilloscope has been my tool of choice to date.

The process is easy, but a little cumbersome, so I decided to design and build a self-contained device to do the identification for me. It also represented an opportunity to build it as another of my 'under the shelf' units, which are incredibly useful.

You can see the project video here:

https://youtu.be/pemhjIltmU4