This fix was actually carried out during the summer, 2018.
A friend of mine brought over a broken formula making machine for me to look at. It had been stored after their first child had out-grown it and since having another baby, it was now needed again, urgently. Following a couple of years in storage, it was brought out, plugged in and after briefly coming on, it failed. No lights, no hope.
These machines save time and effort by allowing water to be heated rapidly and mixed exactly with the formula powder, to produce consistent results every time, perfect for new exhausted parents in the middle of the night. So it was important that I got this working quickly.
After removing the back, I was presented with an electronic control unit, some solenoid valves and a heater, plus some other environmental sensors such as thermostats. The plug fuse was OK, so it was time to check if power was getting to the machine. It wasn’t.
This machine features a couple of power control devices; two thermal aluminium ‘can-style’ fuses in-line with the heater, plus a thermostat on the output of the heater itself (to regulate heat). After testing for continuity, it appeared that one of the can fuses had failed.
These fuses are common across a wide range of appliances, such as coffee machines, fans etc and are cheap, just a few pounds. It could be that a temporary air-lock in the heater caused a hot-spot and therefore that excess heat caused the 172 degree fuse to pop. It was worth a try to replace it and see what happened.
I replaced the fuse and re-assembled. After filling with water and powering it up, normal service was resumed.
Since I replaced the fuse, the machine has been in continuous service for many months, so I can conclude that it was probable that the over heating was temporary.
I created a short video to help others who may have similar problems with their machine.
Cost of a new machine: £90. Cost of repair: a few quid and a few beers.