Modicon AS-B800 Series Modules

Technical Dossier

Product Details And Specifications

Modicon AS-B800 Series: Comprehensive Module Range and Technical Overview

The Modicon AS-B800 series represents one of the most widely deployed discrete and analog I/O module families in legacy programmable automation controller (PAC) and PLC infrastructure across global heavy industry. Installations of this series remain active in petrochemical refineries, pulp and paper mills, water treatment facilities, nuclear auxiliary systems, and continuous process manufacturing plants across North America, Europe, and Asia-Pacific. The installed base is substantial: many facilities commissioned in the 1980s and 1990s built entire control architectures around Modicon 800-series backplane systems, and the cost of wholesale migration to modern platforms — including re-engineering, re-validation, and production downtime — routinely exceeds seven figures. For plant engineers and asset managers operating under capital expenditure constraints, maintaining and sourcing AS-B800 series components is not a workaround; it is a deliberate, defensible asset protection strategy.

The Evolution of AS-B800 Series Architecture

The Modicon AS-B800 series was developed as part of the broader Modicon 800 platform, designed to interface with Modicon 984 and 484 series programmable controllers via the Modbus and Modbus Plus communication backbones. The architecture is based on a passive backplane with active I/O modules that communicate through a parallel bus structure — a design that prioritized deterministic scan-cycle performance over the packet-switched architectures that would later dominate fieldbus and industrial Ethernet generations.

Early variants of the AS-B800 series used discrete transistor-level logic for signal conditioning, with later revisions incorporating surface-mount components and improved noise immunity for high-EMI industrial environments. The series was designed for DIN-rail and panel-mount enclosures, with modules keyed to prevent incorrect insertion — a mechanical interlock that remains relevant when sourcing replacement units, as module revision compatibility must be verified against the host controller firmware version.

Schneider Electric (which acquired Modicon from AEG in 1994) continued to support the 800 series through the late 2000s before formally transitioning customers toward the Modicon Quantum and M340 platforms. As of the mid-2010s, the AS-B800 series entered end-of-life status, with factory repair and new manufacture discontinued. Field replacements now depend entirely on aftermarket inventory, certified refurbishment, and cross-compatible substitution — all areas where procurement lead times can extend to 8–16 weeks without a qualified distributor relationship.

AS-B800 Series Full Catalog & Functionalities (SKU List)

The following SKUs represent confirmed members of the Modicon AS-B800 module family. Each entry reflects the module's primary functional classification within a Modicon 984-based control system.

Discrete Input Modules (DI)

• AS-B805-016: 16-point 24 VDC discrete input module, sink/source compatible, standard density
• AS-B805-032: 32-point 24 VDC discrete input module, high-density configuration
• AS-B806-016: 16-point 120 VAC discrete input module, optically isolated
• AS-B806-032: 32-point 120 VAC discrete input module, panel-mount high density
• AS-B807-016: 16-point 240 VAC discrete input module, high-voltage industrial input

Discrete Output Modules (DO)

• AS-B815-016: 16-point 24 VDC discrete output module, transistor sourcing type
• AS-B815-032: 32-point 24 VDC discrete output module, high-density transistor output
• AS-B816-016: 16-point 120 VAC triac output module, zero-crossing switching
• AS-B817-016: 16-point relay output module, dry contact, 2A per point
• AS-B818-016: 16-point 24 VDC sinking output module, protected outputs

Analog Input Modules (AI)

• AS-B825-008: 8-channel analog input module, 4–20 mA / 0–10 V selectable, 12-bit resolution
• AS-B826-008: 8-channel analog input module, thermocouple types J/K/T/E, cold junction compensated
• AS-B827-004: 4-channel RTD input module, Pt100/Pt1000, 3-wire configuration

Analog Output Modules (AO)

• AS-B835-004: 4-channel analog output module, 4–20 mA, 12-bit resolution, loop-powered
• AS-B836-004: 4-channel analog output module, 0–10 V, short-circuit protected

Communication & Specialty Modules

• AS-B875-001: Modbus Plus network adapter module for AS-B800 backplane integration
• AS-B880-001: ASCII/BASIC communications module, serial RS-232/RS-485 dual port

Sourcing Hard-to-Find & Obsolete AS-B800 Series Parts

The AS-B800 series reached end-of-manufacture status under Schneider Electric's product lifecycle policy. New units are no longer produced. The global supply of serviceable modules is finite and distributed across industrial surplus channels, decommissioned plant inventories, and specialist distributors.

DriveKNMS maintains a dedicated procurement network for Modicon legacy hardware. For AS-B800 series modules, this includes direct sourcing from decommissioned North American and European process plants, cross-referencing against Schneider Electric's historical part number database to identify revision-compatible substitutes, and maintaining bonded stock of high-turnover SKUs such as the AS-B805-016 and AS-B816-016.

For plant managers evaluating the cost of continued AS-B800 operation versus platform migration: a single unplanned production stoppage caused by an unavailable I/O module in a continuous process environment typically costs more than a 12-month forward stock of critical spare modules. Establishing a managed spare parts inventory — covering the top 5–8 module SKUs in active use — is the lowest-cost risk mitigation available for facilities not yet scheduled for DCS migration.

Quality Control for the AS-B800 Series Range

The AS-B800 series presents specific reliability challenges that require targeted inspection protocols beyond standard functional testing. DriveKNMS applies the following procedures to all AS-B800 modules prior to dispatch:

• Backplane connector inspection: The 96-pin DIN 41612 edge connector is inspected under magnification for pin deformation, oxidation, and solder joint fatigue — the primary failure mode in modules removed from long-term service.
• Electrolytic capacitor assessment: Modules manufactured prior to 1998 are subject to capacitor ESR (equivalent series resistance) measurement. Capacitors showing ESR deviation beyond 20% of rated value are replaced with equivalent-specification components before the module is classified as serviceable.
• Optical isolator verification: All discrete I/O modules undergo point-by-point channel testing at rated voltage to confirm isolator integrity. Leakage current is measured and compared against original Modicon specification sheets.
• Firmware and EEPROM verification: Where applicable, module configuration EEPROMs are read and compared against known-good reference images to detect corruption from power cycling or ESD events.
• Thermal cycling burn-in: Modules are subjected to a 4-hour powered burn-in cycle across the operating temperature range (0–60°C) to surface latent component failures before shipment.

Modules that pass all five stages are classified as Certified Refurbished – Grade A and shipped with a test report. Modules that pass functional testing but show cosmetic wear are classified as Grade B and priced accordingly. No module is shipped without documented test results.

For AS-B800 series availability, cross-reference requests, or bulk spare parts procurement:

• Email: [email protected]
• WhatsApp: +86 18359293191
• Web: driveknms.com