Richdel 476PR Controller: Blank Display but Humming Case

Diagnosis: Failed Controller Circuit Board

A Richdel 476PR with a blank LED display but audible transformer hum indicates the power supply is working but the microcontroller/display circuit has failed.

Not Worth Repairing

Richdel (now Irritrol) controllers of this vintage have obsolete circuit boards. Replacement is the only practical option.

Before Replacing: Label All Wires

1. Disconnect each field wire from the controller terminals.
2. Label each with its terminal number (1, 2, 3, 4, C, MV, etc.).
3. Take a photo for reference.

Valve Handle Orientation

For manual ball valves in the valve box: Parallel to pipe = ON, Perpendicular = OFF. Ensure all are open before testing the new controller.

Recommended Resource

irrigationtutorials.com offers wiring diagrams and controller selection guides.