#3 is also sometimes not a problem, many devices work with a bit lower or higher voltage. It’s because the DC to DC converter that is used to control the voltage for the device itself is tolerant enough.
Sometimes devices are multiple volts tolerant with the caviate that the components get warmer with higher input voltage and therefore the device could have reduced life expectency. If the devices where not tolerant especially for lower voltages a slightly bad cable or a long cable could drop the voltage enough so the device wouldn’t function.
That is going to result either in a bang or nothing happening.
You can use a power supply if:
the plug fits
the polarity is correct ( - and + are at the correct location)
the voltage matches
the current and wattage is the same or higher
#4 is subtle. It might work with less current, but this is a caveat not appropriate for novices.
#3 is also sometimes not a problem, many devices work with a bit lower or higher voltage. It’s because the DC to DC converter that is used to control the voltage for the device itself is tolerant enough.
Sometimes devices are multiple volts tolerant with the caviate that the components get warmer with higher input voltage and therefore the device could have reduced life expectency. If the devices where not tolerant especially for lower voltages a slightly bad cable or a long cable could drop the voltage enough so the device wouldn’t function.