Key Technical Specifications
- Product Number: 3BSC950193R1
- Connector Type: DB25P (25-pin Male)
- Mounting Style: Screw-fixed to DIN rail or panel
- Bus Type: CEX Communication Bus
- Required Position: Last unit on CEX bus segment
- Net Weight: 0.04 kg
- Dimensions (HxWxD): 16 mm x 50 mm x 55 mm
- Operating Temp: 0°C to 55°C
- RoHS Status: Compliant (Verify specific batch)
- WEEE Category: Out of Scope
Product Introduction
ABB TB850 serves as the mandatory termination point for CEX bus segments in AC 800M controller systems. Without this module, communication errors and data loss occur due to signal reflections on the unterminated bus line.This terminator uses a standard DB25P male connector and must always be installed on the final physical node of the CEX bus chain. Field experience confirms that missing terminators cause intermittent faults that are nearly impossible to diagnose without bus analysis tools. (Always photograph the bus layout before removing the old unit.)
Installation & Configuration Guide
Preparation (10 min)
- Verify system is in maintenance mode.
- Confirm TB850 is the only required terminator for this segment.
- Check DB25P pins for corrosion or bending.
- Gather screwdriver (typically #2 Phillips or slotted).
Removal (5–10 min)
- Power down the CEX bus segment if possible.
- Unscrew the existing terminator mounting screws.
- Gently pull the DB25P connector straight out.
- Inspect the socket on the preceding module for damage.
Installation (10 min)
- Align TB850 DB25P connector with the last module’s socket.
- Push firmly until fully seated. (Do not force at an angle.)
- Secure mounting screws to prevent vibration loosening.
- Verify no other terminators exist on this bus segment.
Power-On & Test (10 min)
- Restore power to the CEX bus.
- Check controller diagnostics for “Bus Terminator Missing” alarms.
- Verify communication status LEDs on adjacent modules.
- Confirm no intermittent errors appear in the event log.
Troubleshooting Quick Reference
| Symptom | Probable Cause | Corrective Action |
|---|---|---|
| Intermittent CEX errors | Missing terminator | Install TB850 at physical bus end |
| Complete bus failure | Wrong connector type | Verify DB25P male (not female TB851) |
| Connector won’t seat | Bent pins or debris | Inspect socket; clean or replace module |
| Error persists after install | Terminator in wrong position | Move TB850 to true last node |
| Physical damage to connector | ESD or mechanical stress | Replace TB850; inspect ESD precautions |
Dimensions, Mounting & Wiring Notes
- Height: 16 mm
- Width: 50 mm
- Depth: 55 mm
- Mounting: Screw-fixed (no DIN rail clip)
- Connector: DB25P Male (soldered internal termination resistors)
- Wiring Note: No field wiring required. This is a passive termination module.
- Torque Spec: Hand-tighten screws; do not over-torque to avoid stripping plastic threads.
FAQ
Can I use TB851 instead of TB850?
No. TB851 has a DB25S (female) connector. TB850 has DB25P (male). They are not interchangeable. Using the wrong gender will physically damage the bus connector.I installed it but still get bus errors. What now?
Check if you have two terminators on the same segment. Only one TB850 is allowed per CEX bus. Also verify the terminator is truly at the physical end, not just the logical end.Is this new or refurbished?
We stock New Original (New Surplus) units. All units undergo incoming inspection and functional verification. Condition is explicitly stated on each listing. Never assume condition without verification.Do I need special tools to install this?
No. A standard #2 Phillips or slotted screwdriver is sufficient. Avoid magnetic-tip drivers near the DB25P connector to prevent metal shavings from entering the socket.What happens if I forget the terminator?
Signal reflections cause data corruption. You’ll see intermittent CEX errors, module dropouts, or complete bus failure. This is one of the most common field mistakes during AC 800M expansion.Can I use this on older AC 800M hardware?
Generally yes, but verify the CEX bus revision. Early AC 800M versions used different bus architectures. Cross-reference 3BSC950193R1 with your controller’s hardware manual before ordering.Why does the connector feel loose?
DB25P connectors have intentional tolerance for repeated mating cycles. If it feels excessively loose or won’t latch, inspect the socket on the parent module. A worn socket requires module replacement, not just a new TB850.
