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Key Technical Specifications
| Parameter | Value / Specification |
| Catalog Number | 1756-OF8 |
| Outputs Per Module | 8 single-ended outputs |
| Output Ranges | ±10V DC, 0 to 10V DC, 0 to 5V DC, 0 to 20 mA, 4 to 20 mA |
| Resolution | 15 bits across 21 mA (650 nA/bit) or 15 bits across 10.4V (320 µV/bit) |
| Backplane Current Draw | 150 mA @ 5.1V DC, 120 mA @ 24V DC |
| Total Backplane Power | 3.65 W |
| Module Thermal Dissipation | 3.01 W (Voltage mode) / 4.10 W (Current mode) |
| Isolation Voltage | 250V continuous, output-to-backplane (no channel-to-channel isolation) |
| Drive Capability | Current: 0 to 750 Ω load; Voltage: >1,000 Ω load |
| Settling Time | <2 ms to 95% of final value |
| Compatible Terminal Blocks | 1756-TBNH (20-pin NEMA screw clamp), 1756-TBSH (20-pin spring clamp) |
| Operating Temperature | 0 to 60°C (32 to 140°F) |
Product Introduction & Supply Chain Strategy
This product is a Brand New Surplus unit. It is not used, not pulled from a decommissioned plant, and not refurbished. All modules undergo rigorous quality verification to ensure OEM-level reliability. The Allen-Bradley 1756-OF8 is an 8-channel ControlLogix analog output module configured for precise process control applications, driving variable frequency drives (VFDs), control valves, and signal converters across continuous processing systems.
Sourcing this module as New Surplus offers a strategic buffer against extended OEM production backlogs while eliminating the catastrophic risks of second-hand hardware. Refurbished analog cards often exhibit uncalibrated DAC drift, dried filter capacitors, or degraded output transistors that introduce system instability. Securing verified New Surplus maintains full 15-bit conversion accuracy, preserves loop stability, and yields a significantly lower Total Cost of Ownership by preventing unexpected shut-downs of critical process loops.
Installation & Configuration Guide
1.Pre-Installation (Prep & Safety):Safety warning: Verify LOTO and static grounding before handling.
Execute complete Lock-Out/Tag-Out (LOTO) procedures on the cabinet power supply and field loops. Fasten a grounded ESD wrist strap to an unpainted chassis earth point. Open the module housing cover, document the existing terminal block connections, and verify signal shielding is grounded at one end only to prevent ground loops.
2.Removal:
Unscrew the top and bottom retaining screws on the 20-pin Removable Terminal Block (RTB). Pull the RTB straight forward to disengage it without putting strain on the field wiring harness. Squeeze the top and bottom chassis tabs on the 1756-OF8 module and pull the card straight out along its slot guides.
3.Installation (Clone & Seat):
Unbox the replacement 1756-OF8 inside an ESD-safe workspace. Inspect backplane connector pins for straightness and alignment. Slide the module into the designated ControlLogix slot until both top and bottom latches snap securely into place. Reattach the RTB housing and firmly tighten the securing screws.
4.Power-On & Testing:
Reapply backplane power and field loop power. Observe the OK LED: a solid green light confirms valid backplane communication and POST completion. Using Studio 5000 / RSLogix 5000, verify output channel tags, force a test signal (e.g., 12 mA or 5V DC), and measure field terminal points with a calibrated multimeter to confirm accurate scaling.
1756-OF8
1756-OF8
Firmware/Software Versions & Upgrade Notes
- Recommended Firmware: Major Revision 3.001 or higher (ensure Studio 5000 I/O configuration matches physical card firmware).
- Compatibility: Compatible with all 1756 ControlLogix chassis and L6, L7, and L8 controllers. When swapping modules in active projects, set Electronic Keying to “Compatible Module” to prevent backplane configuration faults caused by minor revision updates.
- Upgrade Warning: Firmware flashes should never be performed over an active or unstable network connection. Interrupting power or communication during a firmware flash risks bricking the onboard microprocessor, requiring factory-level re-flashing. Always verify existing firmware parameters prior to field replacement.
Frequently Asked Questions (FAQ)
Why is this module priced higher than refurbished 1756-OF8 cards listed elsewhere?
This module is genuine New Surplus with zero operational wear and full expected component life. Refurbished analog modules frequently suffer from thermal stress and uncalibrated digital-to-analog converters (DACs), leading to drift in 4–20 mA signals. A signal drift of just 0.5 mA can cause a control valve to misalign, leading to product off-spec issues or emergency plant trips that cost exponentially more than the initial purchase savings.
Are these units genuine Allen-Bradley original parts?
Yes. We guarantee that every 1756-OF8 module supplied is 100% Original OEM New Surplus. They originate from verified project overstock, panel builder surplus, or plant reserves. Every card passes visual inspection, backplane handshake testing, and channel output verification before shipment.
Does the 1756-OF8 feature channel-to-channel isolation?
No. The 1756-OF8 is a non-isolated module (all 8 outputs share a common return point). Continuous 250V AC isolation exists between the output group and the ControlLogix backplane, but not between individual channels. If your application requires channel-to-channel isolation to prevent loop interaction, consider the 1756-OF8H (HART) or 1756-OF4I isolated analog output module.
Do I need to recalibrate the 1756-OF8 when installing it out of the box?
No. Every module comes factory-calibrated. However, Studio 5000 allows user-defined scaling (such as engineering units) in the module properties page. Upon establishing communication, the ControlLogix processor automatically pushes the user scaling parameters to the module across the backplane.
What warranty is included with this New Surplus 1756-OF8 module?
We provide a comprehensive 1-year replacement warranty on all New Surplus 1756-OF8 modules. In the rare event of a hardware failure under normal operating conditions within 12 months of purchase, we will replace the card immediately from our stocked inventory.
