DEC H7082-AB Power Supply Module – PDP-11 BA11 Series

DEC H7082-AB: Regulated DC Power Supply Architecture for PDP-11 BA11 Backplane Environments

The DEC H7082-AB is a factory-original regulated DC power supply module engineered by Digital Equipment Corporation for deployment within PDP-11 series minicomputer enclosures — specifically the BA11-S, BA11-N, and BA11-M backplane chassis families. Unlike generic switching supplies, the H7082-AB was designed from the ground up to satisfy the precise multi-rail voltage demands of DEC’s Q-bus and Unibus board ecosystems, where output ripple tolerance and transient response directly determine processor stability and I/O determinism.

In legacy distributed control system (DCS) and SCADA architectures that continue to operate on PDP-11 hardware — particularly in utilities, defense installations, and long-lifecycle manufacturing lines — the H7082-AB remains the lowest-risk power source. Its direct backplane connector interface eliminates the cabling adaptation overhead that third-party substitutes invariably introduce, and its OEM-validated output rails remove the need for field re-qualification of downstream logic boards.

Real-time Stock & RFQ: [email protected] | WhatsApp: +86 18359268345

Technical Parameters

Hardware Logical Analysis

The H7082-AB employs a linear regulation topology on its +5 VDC primary rail — a deliberate architectural choice that prioritizes output noise floor over conversion efficiency. In environments where Q-bus memory boards and CPU modules share a common ground plane, switching-mode noise injected onto the +5 V rail can manifest as intermittent parity errors or bus arbitration failures. The H7082-AB’s linear stage suppresses high-frequency ripple to levels below the noise immunity threshold of standard TTL logic families (typically <50 mV peak-to-peak), a characteristic that switching-mode replacements cannot match without additional LC filtering.

The ±12 VDC rails serve the analog front-end circuitry of DEC’s ADV11, AAV11, and KWV11 interface modules. These rails are regulated independently via discrete pass transistor stages, ensuring that load transients on the +5 V digital rail do not cross-couple into the analog reference domain — a critical isolation requirement for systems performing real-time analog-to-digital conversion in process control loops.

Thermal management is handled by a dedicated fan assembly mounted to the module’s exhaust plenum. The fan operates at a fixed speed, providing deterministic airflow across the pass transistor heatsinks regardless of ambient temperature variation. This contrasts with variable-speed fan designs that introduce acoustic and electrical noise during speed transitions. The thermal shutdown circuit activates at a junction temperature threshold calibrated to protect the pass transistors before thermal runaway can propagate to adjacent backplane slots.

EMC performance of the H7082-AB benefits from its linear topology: the absence of a high-frequency switching stage eliminates the primary source of conducted and radiated emissions in the 150 kHz–30 MHz band. For installations in electromagnetically sensitive environments — such as proximity to high-voltage switchgear or RF transmission equipment — this characteristic reduces the burden on external EMI filtering and shielding infrastructure.

The overcurrent protection circuit uses a current-sense resistor in series with the +5 V output, triggering a latching shutdown when load current exceeds the rated threshold. Recovery requires a manual power cycle, which prevents automatic restart into a persistent fault condition — a safety behavior consistent with IEC 61010-1 requirements for industrial control equipment.

System Integration Benefits

• Zero-adaptation backplane fit: The H7082-AB mates directly to BA11-S, BA11-N, and BA11-M connector arrays without cabling modification, eliminating wiring error risk during field replacement.
• OEM-validated rail tolerances: Output voltages are specified to DEC’s original ±5% tolerance bands, ensuring all downstream Q-bus and Unibus boards operate within their designed supply margins without re-qualification.
• Deterministic bus arbitration support: Stable +5 V delivery with sub-50 mV ripple prevents voltage-induced glitches in Q-bus arbitration logic, maintaining cycle-accurate bus grant sequencing across all installed modules.
• Independent analog rail regulation: Isolated ±12 V stages prevent digital load transients from corrupting analog reference voltages, preserving ADC/DAC accuracy in mixed-signal I/O configurations.
• Latching fault protection: Overcurrent and overvoltage shutdown circuits latch on fault detection, preventing repeated restart attempts that could escalate component damage in downstream boards.
• Low conducted EMI profile: Linear regulation topology eliminates switching-frequency harmonics, reducing interference with co-located communication interfaces (RS-232, RS-422) and analog sensor inputs.
• Thermal shutdown with margin: Junction-temperature-based shutdown activates before thermal stress reaches the pass transistor’s absolute maximum rating, extending module service life in high-ambient installations.
• Maintenance record continuity: Retaining the original H7082-AB part number preserves traceability in regulated industries (defense, utilities, nuclear auxiliary systems) where BOM changes require formal change control documentation.
• Reduced integration engineering overhead: Using the OEM module eliminates the electrical compatibility analysis, connector adaptation design, and functional validation testing that third-party substitutes require.
• Proven field reliability: Units sourced from verified industrial decommissions carry documented operational history, providing a reliability baseline that new-manufacture equivalents cannot offer for legacy system contexts.

Quality Assurance & Global Logistics

Every H7082-AB unit dispatched from our Xiamen facility undergoes a structured pre-shipment test protocol. Output voltages on all three rails are measured under no-load and full-load conditions using calibrated bench instruments, with results logged against the unit’s serial number. Ripple and noise are verified against DEC’s original output specification. Fan operation, thermal shutdown trigger point, and overcurrent latch behavior are each functionally verified before the unit is cleared for shipment.

Units are classified as New Old Stock (NOS) or Tested Refurbished based on physical inspection and operational history documentation. NOS units are sealed in original or equivalent anti-static packaging. Refurbished units are cleaned, re-tested, and packed in foam-lined ESD-safe enclosures with individual test reports included.

From Xiamen, we dispatch via DHL Express, FedEx International Priority, and UPS Worldwide Expedited, with typical transit times of 3–7 business days to North America, Europe, and Southeast Asia. Full commercial invoice, packing list, and HS code documentation are provided for customs clearance. For orders requiring export licensing documentation or country-of-origin certificates, these are prepared on request at no additional charge.

Bulk procurement (5+ units) is supported with priority allocation from reserved stock. Lead time for in-stock units is 1–2 business days to dispatch. For sourced or consolidated orders, lead time is 7–15 business days. All shipments carry a 12-month warranty covering output failure under normal operating conditions, with advance replacement available for critical-uptime applications upon agreement.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
© 2026 siemensplc.com. All rights reserved.