Technical Specifications

FAQ

1. What is the primary function of the 1336-SN-SP3A?
The 1336-SN-SP3A is a converter snubber printed circuit board used in Allen Bradley 1336 STEF drive systems. Its main purpose is to suppress voltage transients and reduce electrical stress generated in the converter power circuit during switching operation. By controlling transient voltage behavior, the snubber circuit helps protect associated power components and supports more stable operation of the drive’s converter section. It is an internal drive component and is not intended to operate as an independent control or power conversion device.

2. Which Allen Bradley drive configuration is the 1336-SN-SP3A designed for?
The 1336-SN-SP3A is designed for the 1336 STEF series and is specifically associated with Frame D configurations. It is identified as a converter snubber board rather than an inverter snubber board, so its application should not be confused with other 1336-SN-SP models designed for the inverter section. Before replacement, the complete drive catalog number, frame designation, electrical configuration, and original board marking should be checked to confirm compatibility.

3. Is the 1336-SN-SP3A an inverter snubber board or a converter snubber board?
The 1336-SN-SP3A is a converter snubber board. Its function is associated with the converter section of the 1336 STEF drive rather than the inverter output section. This distinction is important when selecting replacement parts because Allen Bradley used different snubber board models for different sections and frame configurations of the drive. A visually similar inverter snubber board should not be substituted unless its electrical and application compatibility has been specifically confirmed.

4. What problems can occur if the 1336-SN-SP3A becomes defective?
A damaged converter snubber board can contribute to abnormal voltage transients, converter-related faults, unstable drive operation, or repeated protective trips. Depending on the nature of the failure, the drive may also experience problems during startup or changes in operating conditions. However, these symptoms are not sufficient by themselves to identify the snubber board as the root cause. Problems with rectifiers, SCRs, DC bus components, incoming power, wiring, or other protection circuits can create similar symptoms. A complete inspection and electrical diagnosis should therefore be performed before replacing the board.

5. What should be checked before replacing the 1336-SN-SP3A?
The first step is to verify the original part number and confirm that the drive uses the appropriate 1336 STEF Frame D configuration. The existing board should then be inspected for burned components, discoloration, cracked components, damaged terminals, electrical arcing, or evidence of overheating. The associated converter power components and wiring should also be examined because a failed snubber board may be the result of another electrical problem. If the underlying fault is not corrected, a replacement board could be damaged again after the drive is returned to service.

6. What safety precautions are required when servicing the 1336-SN-SP3A?
The 1336-SN-SP3A is installed inside a high-energy variable frequency drive, so servicing must be performed with the drive completely isolated from its power source. After disconnecting the incoming supply, sufficient time must be allowed for the DC bus capacitors to discharge. The actual residual voltage should be verified with appropriate test equipment before internal components are touched. Technicians should also follow applicable lockout/tagout procedures and use suitable ESD protection when handling the PCB. Working on the board while the drive is energized can expose personnel to hazardous voltage and may cause severe damage to the equipment.

7. How can the compatibility of a replacement 1336-SN-SP3A be verified?
Compatibility should be checked using the complete drive model and catalog information rather than relying only on the appearance of the circuit board. The drive series, Frame D configuration, original snubber board number, circuit function, and electrical arrangement should all be considered. Because the 1336 family contains separate converter, inverter, pre-charge, and other specialized circuit boards, similar-looking components may have completely different applications. Comparing the identification marking on the original board with the drive’s technical documentation is recommended before installation.

8. What checks should be performed after installing a replacement 1336-SN-SP3A?
After installation, verify that the PCB is securely mounted and that all connectors, terminals, and associated wiring are correctly positioned. The drive should be inspected for loose hardware, damaged wiring, foreign objects, or signs of previous overheating before power is restored. Once the drive is safely energized, check for abnormal fault indications and verify that the converter section operates normally. A controlled startup and gradual operational test should then be performed while monitoring drive status and protective functions. If converter-related faults remain after replacing the snubber board, further investigation should focus on the rectifier or SCR section, DC bus circuit, incoming power, wiring, and other related components rather than assuming that the replacement board itself is defective.