We have this wonderful sewing machine from the mid eighties, a New Home Memory Craft 6000 - instruction book is available here. The brand is also known as “Janome”. This machine can stitch letters and symbols using microprocessor control, sewing “emojis” before that word was widely known.

When it was recently powered on after a few years sat idle, it was completely inert (apart from the work light). A local sewing-machine repair place took a look, said it was blowing fuses repeatedly, indicating a fault on one or other of the PCBs. These were no longer available as spares, and so they considered the machine to be unrepairable.

The following circuit is a very simple water leak detector, which I made 25+ years ago (!!) following my fiancée having a washing machine go wrong and leak all over her apartment.

The circuit is not ideal - there are better designs out there. It was built with ‘what I had in my scrapbox at the time’.  It’s purely analog, relying on the gain of the Darlington pair to provide reasonable on/off behaviour. This can actually be an advantage, as the sound will get louder as the leak becomes more serious and conducts more water.