Product Introduction

The Allen Bradley 1790-T0A8X CompactBlock LDX I/O Expansion Block is an 8-point AC digital output module developed for distributed industrial control applications. It allows compatible CompactBlock LDX systems to control additional AC field devices without requiring a separate, larger I/O assembly.

This model supports a load voltage range of 15–132V AC RMS and a maximum load current of 0.5 A RMS per output. Its eight output channels provide independent switching points for compatible AC loads. The photocoupler-isolated I/O-to-logic interface helps separate field-side output circuits from the internal control logic.

The 1790-T0A8X uses a screw-clamp terminal arrangement, making field wiring and maintenance straightforward. Green channel indicators also help technicians identify output activity when checking the system during installation or troubleshooting.

As an expansion block, the 1790-T0A8X operates with a compatible CompactBlock LDX base block rather than functioning as a standalone DeviceNet adapter. It is intended for existing distributed I/O installations that require additional AC output capacity.

Rockwell Automation lists this model as discontinued, with a discontinuation date of December 31, 2024. It remains relevant to maintenance and spare-parts requirements for installed equipment. When sourcing this module, buyers should verify the complete catalog number, product condition, and compatibility with the existing system.

Technical Specifications

Parameter	Specification
Brand	Allen Bradley
Model	1790-T0A8X
Product Type	CompactBlock LDX I/O Expansion Block
I/O Function	Digital Output
Number of Outputs	8
Output Type	AC Output
Load Voltage Range	15–132V AC RMS
Nominal Supply Reference	110V AC RMS, 60 Hz
Maximum Load Current	0.5 A RMS per output
Minimum Load Current	10 mA RMS
Maximum Off-State Leakage	1.0 mA RMS at 100V AC RMS, 60 Hz
Maximum On-State Voltage Drop	1.3V RMS at maximum load
Maximum Operating Time	1 ms
Maximum Release Time	½ cycle + 1 ms
Isolation	Photocoupler isolation, I/O to logic
Status Indicators	8 green indicators
Wiring Connection	Screw-clamp terminal block, M3.0
Dimensions	104 × 42 × 52 mm
Weight	0.1 kg / 0.22 lb
Product Status	Discontinued

Recommended Related Models

The following Allen Bradley CompactBlock LDX models offer different I/O configurations for related distributed automation applications:

1790-T8A0X – CompactBlock LDX terminal-block module with 8 digital AC inputs.
1790-T0W8X – CompactBlock LDX expansion block with 8 relay outputs.
1790-T8BV8VX – CompactBlock LDX module with 8 universal inputs and 8 sinking outputs.
1790-T8BV8BX – CompactBlock LDX module with 8 universal inputs and 8 sourcing outputs.
1790-T16BV0X – CompactBlock LDX module with 16 universal digital inputs.

Popular Related Models

Other models and accessories in the Allen Bradley CompactBlock LDX family include:

1790-0W8X – 8-channel relay output expansion block.
1790-0V16X – 16-channel sinking output expansion block.
1790-0B16X – 16-channel sourcing output expansion block.
1790-8BV8VX – 8 universal input / 8 sinking output expansion block.
1790-8BV8BX – 8 universal input / 8 sourcing output expansion block.
1790-7CMCBL – CompactBlock LDX I/O expansion ribbon cable, 7 cm.
1790-15CMCBL – CompactBlock LDX I/O expansion ribbon cable, 15 cm.

When selecting a replacement, confirm the AC output requirements, terminal-block wiring arrangement, and compatibility with the installed CompactBlock LDX base block.

Applications

The Allen Bradley 1790-T0A8X CompactBlock LDX I/O Expansion Block is an 8-channel, 120V AC digital output module designed for distributed industrial automation systems. It extends the output capacity of compatible CompactBlock LDX installations and provides switching interfaces for AC-operated field devices.

Typical applications include:

Industrial Machine Control: Switching compatible AC loads in automated machinery and production equipment.
Factory Automation: Expanding digital output capacity in distributed control systems.
Conveyor Systems: Controlling AC-operated auxiliary equipment and switching devices.
Packaging Equipment: Providing additional output channels for machine operations and process sequences.
Process Control: Switching compatible AC field devices as part of a DeviceNet-based I/O architecture.

Key Features and Advantages

1. Eight AC Output Channels

The 1790-T0A8X provides 8 digital output points, allowing a single expansion block to control multiple compatible AC loads.

2. 120V AC Output Design

Designed for AC field applications, the module supports a load voltage range of 15–132V AC RMS, making it suitable for specified industrial AC switching requirements.

3. Individual Output Status Indication

Eight green status indicators provide visual feedback for output operation, helping technicians monitor channel activity during commissioning and maintenance.

4. Photocoupler Isolation

The I/O circuitry uses photocoupler isolation to provide electrical separation between the field output circuits and internal logic.

5. Screw-Clamp Wiring

The terminal-block design supports direct field wiring and provides a practical connection method for industrial control cabinets.

6. Compact Installation

Its compact housing helps save panel space and allows the expansion block to be installed in space-constrained control equipment.

Technical FAQs

Q1: What is the primary function of the 1790-T0A8X?

It adds 8 digital AC output channels to a compatible Allen Bradley CompactBlock LDX I/O system.

Q2: How many output channels does this module provide?

The module provides 8 non-isolated output points.

Q3: What type of output does the 1790-T0A8X support?

It provides 120V AC-class switching outputs for compatible AC field loads.

Q4: What is the supported load voltage range?

The specified load voltage range is 15–132V AC RMS.

Q5: What is the maximum load current per output?

The maximum load current is 0.5 A RMS per output. The connected load must remain within the specified electrical limits.

Q6: What is the minimum load current?

The specified minimum load current is 10 mA RMS.

Q7: Does the module provide output status indicators?

Yes. It includes eight green status indicators for monitoring the output channels.

Q8: What type of wiring connection does this model use?

It uses a screw-clamp terminal block with M3.0 terminals. The specified maximum screw torque is 7 lb-in.

Q9: Does the 1790-T0A8X provide isolation?

The I/O-to-logic interface uses photocoupler isolation. The field power circuit itself is specified as non-isolated, so the installation must follow the product's wiring requirements.

Q10: What should be checked when an AC output does not operate correctly?

Check the field AC supply, output wiring, external fuse, load current, terminal connections, and controller output command. Also inspect the channel status indicator and confirm that the connected load is within the module's specified operating range.

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