Fixing a head torch with intermittent switch.

This seems to be a really common problem due to the use of very simple tactile buttons that are prone to contact corrosion with moisture and chemicals.
There are lots of different types of these switches on eBay if you search for tactile switch. The tactile bit refers to the way the contact disk momentarily deforms with a distinct click and detectable finger sensation when it operates.

Another common place for these switches to fail is in vehicle remote key fobs.

The switches are very cheap due to their simplicity and mass production. Here's a typical eBay search:-
https://www.ebay.com/sch/i.html?_from...
Note that there is a wide range of styles and sizes. The type I used in the video has an actuator shaft that is available in several heights. I happened to have the right size on hand.

The battery test indicated that the cells have half the capacity that is printed on them. 1100mAh instead of 2200mAh. That's actually a good result for this type of product. Some ship with the cheapest and lowest capacity 18650s that they can find.

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