Sometimes, a classic tool needs a bit of love to make it work again. Other times, you find something new which falls just slightly short of perfect. In either case, there's no need to go on the hunt for a replacement when you can hack the required functionality into the tool you already have - as with Simon Ludborzs' recent overhaul of his Hakko 936 soldering station.
Hakko's range of temperature-controlled soldering stations are well regarded, and even the older models are sought-after by makers and tinkerers for their excellent build quality and performance. There's a catch, though, in the form of a slight design flaw: the on-board indicator LED lights only when the station is actively heating the iron tip. As a result, it's possible to glance at your station and assume it's off only to find that you return home to - at best - a raised electricity bill caused by leaving the poor iron sweating all day.
Simon's solution, like other Hakko owners before him, is to modify the soldering station to have a two-colour notification LED: green for power on and red for active heating. Based on an existing project, the modification does suffer somewhat from a bootstrapping issue - you'll need another soldering iron to modify the Hakko's circuit board to accept the new LED - and shouldn't be attempted by anyone without experience in mains-powered electronic hardware. For the brave, though, it's a great way to boost the functionality - and, providing the modification is done carefully, safety - of a classic tool nowhere near the end of its useful service life.
With the 24V AC supply feeding the RGB led through a single dropping resistor, and by only switching on / off the Red LED, I can exploit the differences in forward voltage of the Red and Green LEDs to get a Green on / Red Heating display, rather than the Yellow on / Red Heating that Daniel achieved.