Siemens 6ES5734-1BD20 Retrofit-Ready PG Cable for S5 Control Systems
The Siemens 6ES5734-1BD20 is a dedicated programming cable designed for the SIMATIC S5 series of programmable logic controllers. As legacy S5 installations continue to operate across manufacturing plants, chemical facilities, power generation sites, and process automation environments, the demand for reliable, drop-in replacement programming cables remains critical. This unit serves as a direct retrofit solution for engineers and maintenance teams managing aging S5 control architectures — enabling uninterrupted program uploads, downloads, and online diagnostics without requiring hardware platform migration.
Whether you are restoring a failed programming interface on an existing S5-115U rack, performing a scheduled maintenance cycle on an S5-135U system, or preparing a control cabinet for a phased migration toward the SIMATIC S7-300 or S7-400 platform, the 6ES5734-1BD20 provides the physical and electrical compatibility required for seamless integration. Each unit is tested prior to shipment and backed by a 12-month warranty, ensuring confidence in both new deployments and emergency replacement scenarios.
Upgrade Compatibility Table
| Parameter | Details |
|---|---|
| SKU / Part Number | 6ES5734-1BD20 |
| Compatible PLC Series | SIMATIC S5-90U, S5-95U, S5-100U, S5-115U, S5-135U, S5-155U |
| Interface Type | PG (Programmer) Port — TTY / RS-232 compatible |
| Installation Requirement | No additional hardware adapter required for standard S5 CPU modules |
| Communication Compatibility | Compatible with STEP 5 programming software; supports online monitoring and program transfer |
| Replacement Recommendation | Direct drop-in replacement for original 6ES5734-1BD20; verify cable pinout against local wiring diagram before installation |
| Commissioning Notes | Confirm COM port assignment in STEP 5; set baud rate to match CPU configuration; verify TTY loop current if using older PG 685/750 programmer units |
| Warranty | 12 Months — covers manufacturing defects and interface failure under normal operating conditions |
Retrofit Planning for Existing Automation Systems
Integrating the 6ES5734-1BD20 into an existing S5 retrofit project requires a structured approach to avoid unplanned downtime and configuration errors. Before connecting the programming cable, maintenance engineers should verify the CPU module type installed in the S5 rack — common variants include the 6ES5315-8MA11 (CPU 315) and 6ES5451-8MR11 (digital output module) — as the PG port location and pinout may differ slightly between CPU generations.
Power supply integrity is a prerequisite for any programming session. Confirm that the 6ES5955-3LC41 or equivalent S5 power supply module is delivering stable 24 VDC to the backplane before initiating a connection. Unstable rail voltage during a program download can corrupt the user memory block and require a full CPU initialization cycle.
For systems using the 6ES5700-8MA11 SINEC L1 communication processor or the 6ES5521-8MA11 serial interface module, confirm that the programming cable does not conflict with active communication tasks on shared backplane slots. In multi-rack configurations using the 6ES5705-0AB10 expansion interface module, the programming session should be isolated to the central rack CPU to prevent address conflicts during online editing.
When the retrofit scope includes I/O expansion — for example, adding 6ES5482-8MA11 analog input modules or 6ES5430-8MB11 digital input modules to an existing rack — the 6ES5734-1BD20 cable is used to update the hardware configuration in STEP 5 and reassign module addresses before the new I/O is brought online. This sequence is critical: address assignment must be completed and verified in the program before the new modules are powered and scanned by the CPU.
For sites planning a phased migration from S5 to S7, the programming cable also supports the final S5 program backup step — a mandatory prerequisite before any SIMATIC S7-300 CPU (such as the 6ES7315-2AH14-0AB0) is installed in the modernized control cabinet. Retaining a verified S5 program archive ensures rollback capability during the transition period.
Downtime Control During System Migration
Minimizing production downtime during a programming cable replacement or broader S5 system migration depends on preparation, sequencing, and verification. The 6ES5734-1BD20 supports hot-swap programming sessions on most S5 CPU variants in STOP mode, allowing engineers to upload the existing program to a laptop running STEP 5 before any physical changes are made to the control cabinet.
The recommended sequence is: (1) connect the 6ES5734-1BD20 to the PG port of the target CPU; (2) upload and archive the complete program including data blocks (DBs), function blocks (FBs), and organization blocks (OBs); (3) document the current I/O module addresses, communication parameters, and any active SINEC H1 or L2 network settings; (4) perform the required hardware change or module replacement; (5) download the verified program back to the CPU; (6) perform a controlled restart and monitor the first scan cycle for fault flags.
For HMI-connected systems — particularly those using SIMATIC OP7, OP17, or TP27 operator panels communicating via the MPI or PPI interface — confirm that the HMI screen tags remain mapped correctly after the program download. A mismatch between HMI variable addresses and the updated DB structure is a common source of post-migration alarms that can be avoided by reviewing the HMI project file before the cutover window begins.
Stocking a verified spare 6ES5734-1BD20 on-site reduces mean time to repair (MTTR) for programming interface failures and eliminates the lead-time risk associated with sourcing legacy Siemens S5 accessories from the open market. Each unit shipped from our inventory is pre-tested and includes a 12-month warranty, supporting both planned maintenance cycles and emergency breakdown scenarios.
Retrofit Support FAQ
Q1: Is the 6ES5734-1BD20 a direct replacement for the original Siemens part?
Yes. The 6ES5734-1BD20 is a direct form-fit-function replacement for the original Siemens programming cable of the same part number. It is compatible with all standard SIMATIC S5 CPU modules that feature a PG port, including the S5-90U, S5-95U, S5-100U, S5-115U, S5-135U, and S5-155U series. No adapter or wiring modification is required for standard installations.
Q2: What commissioning steps are required after connecting the cable?
After physical connection, open STEP 5 on the programming device and navigate to the interface settings to confirm the correct COM port is selected. Set the baud rate to match the CPU’s configured PG communication speed (typically 9600 or 19200 baud for S5 systems). Perform a short online test by reading the CPU status register before initiating any program transfer. If using an older PG 685 or PG 750 programmer, verify the TTY current loop setting is active.
Q3: Can this cable be used during a live migration from S5 to S7?
Yes, for the S5 side of the migration. The 6ES5734-1BD20 is used to perform the final program backup from the S5 CPU before the S7 hardware is installed. This backup is the foundation of the migration archive and should be stored in at least two locations. Once the S7 CPU is installed, a separate PROFIBUS or MPI programming cable compatible with STEP 7 or TIA Portal is required for the S7 commissioning phase.
Q4: What does the 12-month warranty cover?
The 12-month warranty covers manufacturing defects, connector failure, and cable integrity issues under normal operating and storage conditions. Each unit undergoes a pre-shipment functional test to verify signal continuity and connector seating. Warranty claims are processed through our sales team at sales@smartnexmsk.com. Physical damage caused by incorrect wiring, overvoltage, or mechanical stress is not covered under the standard warranty terms.
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