The third instalment in Boldport's Cordwood Puzzle series of soldering kits steps it up a notch with three layers, soldered in the old-fashioned cordwood style.

Here are the and puzzles in the Cordwood series.

In the 1950s and 1960s inventive engineers saved space by using the '' assembly, where components were sandwiched in between two circuit boards. This construction became less useful with reduced component sizes, PCB manufacturing advances, more compact integration, and surface mount technology, but is still a lovely piece of history. Combining both old and new, the Cordwood Puzzle series of projects are a tribute to this construction and to the engineers who came up with it.

The puzzle is to correctly assemble the circuit with the components at hand. Once completed, all of the LEDs light up when power is applied. When connected to a controller board each LED can be individually controlled.

Unfortunately(!), all the comprehensive assembly guides were mysteriously missing from the kits.

Note: requires through-hole soldering!

Cordwood Puzzle Three was project #25 of the Boldport Club.