Overview
When 12VDC is applied to power the board and the 12V jumper, (J1), is selected for reader power, the reader ports will no longer supply power.
Cause
The Reader Power Select option on the LP4502 (J7), LP1502 (J7) & Series 3 boards (J1) has been changed by Mercury. If the supplied voltage is 12Vdc and J1 is in the 12V position, there will be no voltage supplied.
Resolution
Move the Reader Power jumper (J1/J7) to the PT position.
More Information
Reader Power Select Configuration Options For LP4502, LP1502 & MR-52-Series 3 Boards