Here is what you need to know when deciding if an adapter will work for your equipment.
1. Will the connector fit my equipment? If not forget it, the rest of this list doesn't matter.
2. Is the polarity the same. Look for the symbol below on your equipment. Near the plug or on a label on the bottom. The plus + and minus - have to be assigned the same on both. The symbol may only show the plus or the minus that is because the other is assumed. There will never be two pluses or two minus on the same plug. Now look for the same symbol on the adapter.
3. If it fits and the polarity are the same then look at the voltage. The adapter should provide at least the amount required by your device. A couple of volts more probably won't be a problem. Most devices regulate over voltage. So a 18VDC device will be ok with a 20VDC supply, but not a 16VDC supply.
DO NOT PLUG IN AN AC SUPPLY INTO A DC DEVICE!!! VDC = VOLTS DIRECT CURRENT VAC = VOLTS ALTERNATING CURRENT. THEY ARE NOT COMPATIBLE.
4. If everything so far is a match there is one last thing to check. The current. The adapter / supply should supply at least the devices required amperage. The adapter below is rated for 300mA (milliamps). A milliamps is a thousandth of an amp. So 300mA is equal to .3 Amps. Again it's ok if it supplies more. In this case a lot more. Up to double what the device needs, but not less.
I hope this will help you if you ever have to use a substitute power supply or buy a replacement.