To test the AC adapter for the 500 Series PowerBook computers, service providers would need to use test leads for their digital volt meter that have narrow test probes. Adapters are available to clip onto the ends of test probes that would allow the test probe to fit inside of the holes on the AC adapter connectors.
The front of the connector has four holes labeled 1 thru 4. The outer metel shield is ground. All measurements should be made with the negative or common lead of the volt meter connected/touching the outer shield. Use the positive test probe and check for the following DC voltages.
| Connector No. | Signal Name | DC Voltage |
| 1 | VBATT | 16.4 V to 16.6V |
| 2 | VMAIN | 16.4 V to 16.6V |
| 3 | GND | 0V |
| 4 | GND Sense | 0V |