Siemens 2020964-001 Rev AC DPM Base Board for Industrial Control Systems

The Siemens 2020964-001 Rev AC is a DPM (Distributed Power Management) base board, a printed circuit board used in Siemens industrial automation systems, particularly in older Simatic S5 or S7-400 based racks. This board serves as a power distribution and backplane interface module, supplying regulated voltages to I/O modules and providing signal conditioning between the power supply and the CPU. It is typically installed in a subrack (e.g., 6ES7400 series) and is essential for system operation. The “Rev AC” indicates a specific revision with updated components.

Technical Specifications

The board accepts input from a primary power supply (typically 5 VDC and 24 VDC via the backplane) and distributes it to the slots. It includes filtering and overcurrent protection for each slot. The board also handles the communication bus between modules (P-bus and K-bus). The dimensions are approximately 270mm x 18mm (single-wide) and it fits into a dedicated slot (slot 1) of the subrack. The board has test points for voltage monitoring (TP1: +5V, TP2: +24V, TP3: GND). It is rated for operating temperature 0°C to 60°C.

Compatibility and System Usage

The 2020964-001 Rev AC is compatible with Siemens subracks such as 6ES7400-1TA00-0AA0 (18 slots) and 6ES7400-1JA00-0AA0 (9 slots). It is used in Simatic S5-115U, S5-135U, and early S7-400 systems. The board is not hot-swappable; the system must be powered off before removal or installation. It is often paired with a power supply module like 6ES7407-0KA00-0AA0. The Rev AC revision corrects a known issue with capacitor aging in earlier revisions (Rev AB and Rev AA).

Failure Symptoms and Diagnostics

Common signs of a failing DPM base board include: intermittent system resets, certain slots not powering up, communication errors between modules (e.g., I/O access faults), or the CPU failing to recognize modules. Visual inspection may reveal bulging capacitors or burnt traces. The board has a green LED for “Power OK” and red LEDs for “Bus Fault” or “Overcurrent”. Diagnostic software (e.g., STEP 7 hardware diagnostics) may report “backplane bus error”.

Installation and Replacement

To replace the board: power down the rack, remove all I/O modules, unscrew the board from the backplane, and slide it out. Insert the new board, ensuring alignment with the backplane connectors, then reinstall modules. No configuration is required as the board is passive (no user settings). However, the CPU may need to be reset after replacement. Use ESD protection during handling. After replacement, verify voltages at test points with a multimeter.

Environmental Ratings

Operating temperature: 0°C to 60°C, storage -40°C to 85°C. Humidity: 5% to 95% non-condensing. The board is rated IP00 (open) and must be installed inside a control cabinet. It is conformal coated for resistance to moisture and dust. The board meets CE and RoHS standards (for legacy products).

Typical Applications

The 2020964-001 is found in legacy Siemens PLC racks controlling conveyor systems, packaging machines, and process automation. It is a critical component for any system using the S5 or early S7 platform. Many such systems are still in operation due to the high cost of migration.

Ordering and Availability

Order number: 2020964-001 (specify Rev AC). This part is obsolete from Siemens; however, aftermarket suppliers offer repaired or refurbished units. It is also possible to replace the capacitors on an existing board as a repair. Siemens no longer provides official support, but documentation (S5-115U Manual) is available from third-party archives. When ordering a replacement, verify the revision to ensure compatibility with the rest of the backplane.

Important Notes

Do not attempt to use this board in a different subrack without confirming the pinout. The board carries hazardous voltages when the system is powered. Always follow lockout/tagout procedures. This documentation is for reference only; always consult the original Siemens hardware manual for your specific PLC model.