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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Catalog Number | 2706-D21J2 |
| Display Type | Vacuum Fluorescent Display (VFD) |
| Display Format | 2 lines × 16 characters per line |
| Character Type | 14-segment alphanumeric (uppercase) |
| Viewing Distance | Up to approx. 3 m (10 ft) |
| Input Power | 12–24 V DC |
| Power Consumption | Approx. 3–5 W |
| Memory | 2K (stores up to ~94 message blocks) |
| Communication | RS-232 and RS-422 (switchable); parallel port option |
| Enclosure Rating | NEMA Type 12 / 13 compatible |
| Programming | Via Allen-Bradley terminals or compatible ASCII devices |
| Status | Discontinued legacy product |
4. Product Introduction
The Allen-Bradley 2706-D21J2 is a compact Dataliner DL5 series message display that shows two lines of 16 characters each on a vacuum fluorescent display. It is designed for industrial machine status, operator prompts, alarm messages, and simple process information.
The unit operates on 12–24 V DC and communicates via RS-232 or RS-422 serial ports (or parallel input). Messages are stored in onboard memory and triggered by a PLC or other ASCII source. Although the DL5 family is discontinued, these displays remain in use on older equipment where a simple, reliable text display is required. New-surplus and refurbished units provide a practical replacement path.
2706-D21J2
2706-D21J2
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Blank display | Power missing or polarity reversed | ❌ Low | Measure 12–24 V DC at power terminals | Verify power supply and wiring first |
| Display shows garbage or locked | Baud rate or protocol mismatch | ✅ High | Confirm serial settings match the controller | Match baud, parity, and protocol |
| Messages not updating | Trigger signal or memory issue | ✅ High | Check trigger inputs and message download | Re-download messages and verify trigger logic |
| Dim or uneven characters | Aging VFD or low voltage | ✅ Medium | Measure supply voltage under load | Stabilize power; replace unit if tube is worn |
| Cannot communicate | Wrong port selected or cable fault | ✅ High | Verify DIP switch for RS-232 vs RS-422 and cable pinout | Use correct programming/communication cable |
| Unit powers but no response | Internal memory or processor fault | ✅ Medium | Attempt message download from known-good source | Replace unit if download fails |
If the display still does not function after these checks, record the exact behavior, power readings, and communication settings, then contact technical support with photos of the unit and wiring.
6. Frequently Asked Questions (FAQ)
Q: How many lines and characters does the 2706-D21J2 display?
A: Two lines with 16 characters per line on a vacuum fluorescent display.
Q: What power supply is required?
A: 12–24 V DC. Typical power draw is low (approximately 3–5 W).
Q: What communication options are available?
A: RS-232 and RS-422 serial ports (selectable). A parallel port is also supported on the DL5 series.
Q: How much message memory does it have?
A: 2K memory, sufficient for approximately 94 message blocks depending on message length.
Q: Is the 2706-D21J2 still in production?
A: No. It is a discontinued Dataliner DL5 product. New-surplus and refurbished units are the available sources.
Q: Can it be programmed from a modern PC?
A: Yes, using appropriate serial cables and terminal emulation or legacy Allen-Bradley programming tools that support ASCII message download.
Q: What is the difference between the D21J2 and other DL5 models?
A: The “D21” indicates the 2-line × 16-character format. Other variants differ in line count, memory size, or power options.
