Here's the skinny on voltage, current, resistance and power. Sit back, grab a coffee, and enjoy the ride.
Almost everything electrical has resistance. It is defined as "opposition to current flow." Copper wire has resistance.
Voltage can be described as "Pressure". You can have very high voltages, but without current, it's pretty.
Current is the flow of electrons. Too much heats up wires, and starts fires, and current is what makes electricity deadly.
V(voltage) = I(current)/R (resistance ...called "ohms")
Correction. V = I * R, not V = I/R.
Power(in watts) is a function of voltage x current.
In school you learned that you cannot create energy, nor can you destroy it.
This makes those values proportional(inversely) meaning if the resistance is constant, Volts and amps will be proportional to each other. More volts = less amps. and more amps will mean less volts. If you try to power a 12v light with 6 volts, the current doubles and things get real hot!
Current would halve in this situation, not double. And more volts equals more amps, not less. In a simple resistive load, double the volts will double the current will quadruple the power.
You need to give any appliance the proper voltage in order to ensure it's proper operation.
Soooo... Your appliance likes 9 volts... If you feed it higher volts, you will damage the delicate electronics inside. Less volts and the little gizmos won't work properly. It's important to always start with the proper voltage. Now if our appliance says... 10 watts, This means that 10watts / 9 volts = 1.11 amps. Your power supply needs to supply at least that or things will start to smoke.
Wires are rated by size, so your power supply was built with a certain sized wire.Too much current in those wires will melt them and start a fire!!! So if your appliance wants 1500mA @ 9 volts, but your power supply is maxxed at 1300mA, somethings gotta give. My guess is that if a internal fuse doesn't pop, those wires will melt.
Usually, when you start to exceed maximum current capability of a power supply, the voltage starts to cave. But heat would not be uncommon.
Notice how those little transformers run warm?? if you try to get more current, they will run HOT (briefly) Take a pic of your power tap and bring it to a radio shack, they can tell you what type of power supply to get.