Going back to electronic after a 20 years break

You can find these very cheap voltmeters all over ebay. They have a single wire for both power supply and volt measurement. No surprise, they need enough voltage to power up the circuit and display, that is ~ 3.3 v As a result they are  useless to display lower voltage. If we flip them, the power supply part is simple enough : On the Top left,there is a diode marked as D1 (reverse polarity protection), followed by a 7133H  voltage regulator on the bottom left to get 3.3 v. Just remove the diode and connect 5v power supply there Done ! Now you can measure much lower voltage. It might be a good idea to put back a reverse polarity protection diode somewhere ....

Pretty often, a 3d printer  nozzle gets clogged when impurities get stuck in there. You can buy expensive and brittle very fin drill bits or... Use vaping gear (again) : Take a 0.3 mm kanthal, it is a  commonly used size , perfect to unclog a 0.4 mm nozzle. The kanthal can take the heat and is strong enough 1- Heat the nozzle with hot air gun at 200 degrees 2- Push a strand of kanthal inside the hole 3- Remove all the gunk Done ! It is way more gentle that drilling it