The 1336-PB-SP21B PCB or printed circuit board is an Allen-Bradley spare part for the Allen-Bradley 1336 adjustable frequency drives. This spare part PCB is a precharge PCB that operates with a voltage rating of 460 Volts AC. The board resonates in the frequency range of 50 to 60 Hertz. It comes with rated power output of 60 to 800 Horsepower with normal working conditions. The main purpose of a precharge PCB is to minimize the incoming inrush current coming into the system. A high inrush current can damage the internal parts of the adjustable frequency drive or the attached board. This board's job is to help to regulate the inrush current and to protect the drive from electrical damages. The 1336-PB-SP21B PCB is used inside the drive next to the main internal board of the adjustable requency drive. The adjustable frequency drive is mainly used in an industrial system to regulate and maintain the torque and speed of 3-phase induction motors.

The Allen-Bradley 1336-PB-SP21B board or PCB is comprised of different components. The components include a contactor device, a precharge relay, a resistor, and connection jumpers. The PCB is connected to the main device by using the jumpers that are located on the top end of the board. The precharge PCB circuit can also be used to detect problems with the ground isolation, short circuits, and problems within the circuit. The 1336-PB-SP21B PCB is fully compatible with the Allen-Bradley 1336 series, 1336 Plus II series, and the 1336 Impact series of variable frequency drives.