The Allen-Bradley 1336-SN-SP21A PCB inverter is also a precharge snubber board (Common Bus) that is an inverter snubber board for the 1336 Impact, Force, Plus, and Plus II AC drives. It is designed to suppress voltage transients within the drive's circuit, and it is located close to the drive’s heatsink at the back of the inverter assembly. The 1336-SN-SP21A inverter snubber assembly consists of an inverter snubber and some installation accessories that include fastening screws and an installation manual. The 1336-SN-SP21A snubber board can serve as an inverter snubber replacement part for the C frames 1336 Impact, Force, Plus, and Plus II AC drives with 20 to 30 Horsepower output ratings, and a precharge snubber replacement for the C-frame Impact, Force, Plus, and Plus II AC drives with 460 Volts AC voltage ratings and X40 to X60 Horsepower power ratings.

The 1336-SN-SP21A snubber board is an inverter snubber that is found within the power module snubber board, and it should be tested for good working conditions whenever a power module is replaced. Testing is done by using a meter and comparing results with the standard table readings. Replacing the snubber board requires removing power from the drive and checking for the absence of residual voltage at the appropriate terminals. After that, the technicians should detach the control board mounting frame (plate), the precharge board mounting frame, and the inverter assembly to access the snubber board. Disconnect the 2 jumper connectors (J1 and J2) on the board and detach the snubber board from the mounting bracket. Replace the old snubber board with a new one like the 1336-SN-SP21A snubber board and install it by following steps in the reverse order of the removal process.