Dynamic Instrument 2-2633 Power Supply Adapter Charger 7.5V 115mA
Your replacement adapter much match these 5 criteria (disregard if your matching my model number):
1) OUTPUT Volts (V)
2) Amps or milliamps (A or mA)**
3) OUTPUT Current (AC or DC)
4) Tip size***
5) Tip polarity (+ or -). To find tip polarity there is usually a diagram on the adapter that looks like this (+)---- •)-----(-) The line that touches the dot in the middle, in this example its positive, is the polarity of the tip (polarity of the inside of the tip, outside of the tip would be negative.
Be sure your looking at the Output stats. For all the adapters I sell, you can disregard the matching of Input if you are in the United States. Some countries will require 220V. Some of the adapters I sell are rated to 220V and could be used with a converter as the wall sockets are shaped different.
It is important you match all 5 of these criteria or you could underpower your device, causing certain function not to work correctly, if at all. You could also damage your device, ruin the battery pack, create a fire hazard or pop a breaker. The only flexible criteria from the list above is the amps. A device will only use as much amps as it needs and no more. You need to match the amp rating or have MORE amps. If the device needs 300mA, i.e., you can match 300mA or more (400ma and up).
**Milliamps to amps: 1000mA is = 1A (i.e. 1200mA is 1.2A and 300mA is 0.3A)
***Tips are measured in millimeters (mm) for an inner diameter and outer diameter of the circles on the ends of the tip. Alot of adapters are 5.5mm (outer circle) x 2.5mm (inner circle).
NOTE: Not even if you match all the criteria is the adapter guaranteed to work as there are different kinds of current flow, switching adapters, etc etc that is too hard to explain in layman's terms.
Of course the best way to replace an adapter is my finding the model number of the adapter you need that goes to your specific device. It might be in the owner's manual, near the plug in to your device, on the box, or you can call the manufacture to find out.