Product Overview
The Allen-Bradley 1336-PB-SP6C (Rockwell Automation internal reference 74101-181-51) is a factory-designed precharge power board engineered for the Bulletin 1336 PLUS and 1336 PLUS II families of adjustable frequency AC drives. Within the drive’s power conversion architecture, this printed circuit board governs the controlled precharging of the DC bus capacitor bank during startup. Its role is fundamental: by limiting the inrush current that would otherwise surge through the rectifier and into the uncharged capacitors, the 1336-PB-SP6C protects both the DC bus capacitors and the power semiconductors from damaging current spikes.
The Allen-Bradley 1336-PB-SP6C is not a user-programmable control card. It is a dedicated power-stage assembly that performs a single, critical function with precision. When the drive is powered up, the precharge circuit gradually brings the DC bus voltage up to its operating level before the main contactor closes. This controlled ramp prevents the instantaneous high-current event that can weld contacts, stress bridge diodes, and shorten the service life of electrolytic capacitors. Without a functioning precharge board, a 1336 drive may fail to start, trip on overcurrent, or sustain cumulative damage to the power section each time it is energized.
Manufactured to Rockwell Automation’s original specifications, the Allen-Bradley 1336-PB-SP6C features an OEM-matched connector interface and chassis-standoff mounting pattern, allowing it to seat correctly in the designated drive frames without modification. It is compatible with select 1336 PLUS and 1336 PLUS II frame sizes—most commonly Frame D and Frame E configurations—and interfaces directly with the drive’s internal DC bus architecture. Because the Bulletin 1336 platform has been discontinued, the 1336-PB-SP6C is a strategically important spare part for any facility committed to extending the service life of its installed drive fleet.
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1336-PB-SP6C |
| Internal Reference | 74101-181-51 |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | Precharge Power Board / PC Board |
| Compatible Platform | Bulletin 1336 PLUS, 1336 PLUS II |
| Compatible Frame Sizes | Frame D / E (verify against drive nameplate) |
| Primary Function | DC Bus Precharge Control & Inrush Current Limiting |
| Input Voltage Range | 380–480 VAC, 3-phase (per drive rating) |
| Mounting | Internal drive chassis, chassis-standoff mount |
| Connector Interface | OEM-matched multi-pin power connectors |
| Operating Temperature | 0 °C to +50 °C (drive enclosure ambient) |
| Storage Temperature | -40 °C to +70 °C |
| Humidity | 5–95 % RH, non-condensing |
| Altitude | Up to 1000 m |
| Weight | Approx. 0.3 kg |
| Dimensions (W×H×D) | Approx. 245 × 127 × 34 mm |
| Compliance | CE, UL (per parent drive certification) |
Main Features and Advantages
Controlled DC Bus Precharge: The defining function of the Allen-Bradley 1336-PB-SP6C is the controlled energizing of the drive’s DC bus capacitors. At power-up, the uncharged capacitors represent a near-short-circuit load. The precharge board introduces a current-limiting path that allows the bus voltage to rise gradually. Once the capacitors are charged, the main contactor engages and normal drive operation begins. This sequence prevents the violent inrush current that can destroy rectifier diodes, stress contactors, and degrade capacitor life.
Protection of Critical Power Components: By managing the precharge cycle, the 1336-PB-SP6C safeguards the most expensive and vulnerable components in the drive: the DC bus capacitors and the IGBT power modules. A failed precharge circuit can cause repeated overcurrent trips, welded main contactor contacts, or progressive damage to the bridge rectifier. Replacing a faulty board early prevents these secondary failures and can save the entire drive from irreparable damage.
OEM-Matched Form Factor: The Allen-Bradley 1336-PB-SP6C is built to the original Rockwell Automation mechanical and electrical specifications. Its connector layout, mounting hole pattern, and component placement are identical to the board originally installed in the drive. This ensures correct seating, reliable contact engagement, and proper electrical clearance—advantages that aftermarket substitutes cannot reliably match.
Straightforward Board-Level Replacement: Because the precharge function is isolated on a dedicated printed circuit board, a failed unit can be replaced at the component level rather than requiring a complete drive change-out. The 1336-PB-SP6C installs on chassis standoffs using the original mounting points and connects through the drive’s existing internal bus architecture. With proper ESD precautions, the swap can be completed in a fraction of the time required to remove and replace an entire VFD.
Minimized Downtime Risk: For facilities operating legacy 1336 drives, having a spare Allen-Bradley 1336-PB-SP6C on the shelf can be the difference between a brief planned maintenance window and an extended, unplanned production stop. The board’s plug-in compatibility means no firmware changes, parameter adjustments, or drive reconfiguration are required when the correct revision is installed.
