DEC H7082 Power Supply Modules: H7082-AB,

Technical Dossier

Product Details And Specifications

DEC H7082 Series: Comprehensive Module Range and Technical Overview

The DEC (Digital Equipment Corporation) H7082 series comprises regulated DC power supply units engineered for VAX, PDP, and related minicomputer backplane systems. These units were deployed extensively across heavy industrial environments including petrochemical processing facilities, nuclear instrumentation support systems, and continuous-process refinery control architectures where uninterrupted DC bus integrity is a non-negotiable operational requirement. The H7082 series occupies a critical position in legacy DEC system infrastructure: it provides the regulated +5 VDC, +12 VDC, and -12 VDC rails that sustain CPU boards, memory arrays, and I/O subsystems within BA-series enclosures. Installed base estimates place H7082-family units in tens of thousands of active legacy systems globally, the majority of which remain in service under long-term maintenance contracts rather than replacement programs.

The Evolution of H7082 Architecture

The H7082 line was introduced in the mid-1970s as DEC transitioned from discrete linear regulator topologies to switching power supply designs capable of higher efficiency and reduced thermal load within dense backplane enclosures. Early variants such as the H7082-A used ferro-resonant transformer stages for voltage regulation, providing inherent immunity to input line transients — a property valued in industrial grid environments with poor power quality. The H7082-AB revision introduced improved switching frequency control and enhanced overcurrent protection circuitry, extending MTBF ratings and reducing field failure rates in high-ambient-temperature installations.

As DEC's VAX architecture matured through the VAX-11/750, VAX-11/780, and MicroVAX generations, the H7082 series was progressively adapted to support higher current demands from denser CPU and memory configurations. Compatibility across BA11, BA23, and BA123 enclosure families was maintained through standardized connector pinouts, though output current ratings and ripple specifications differ between sub-variants. Engineers maintaining mixed-generation DEC installations must verify the specific revision suffix before substitution, as cross-variant swaps without derating analysis can result in marginal voltage regulation under peak load.

DEC was acquired by Compaq in 1998, and subsequently by Hewlett-Packard in 2002. No new H7082-series units have been manufactured since the late 1990s. The entire series is now in end-of-life status, with all support obligations transferred to the third-party maintenance and surplus parts market.

H7082 Full Catalog & Functionalities (SKU List)

The following SKUs represent verified members of the DEC H7082 power supply family. Each entry reflects a distinct hardware revision or output configuration. Functional descriptions are derived from DEC engineering documentation and field maintenance records.

H7082-A: Original ferro-resonant regulated supply, +5V/+12V/-12V rails, BA11 enclosure primary.
H7082-AB: Revised switching supply with enhanced OCP; primary unit for VAX-11 and MicroVAX BA-series enclosures.
H7082-B: Higher-current +5V output variant; supports expanded memory configurations in BA23 enclosures.
H7082-BA: Revision B with updated EMI filter stage; compliant with later FCC Class A emissions requirements.
H7082-C: Reduced-profile form factor for BA123 enclosure; maintains identical output rail specifications to H7082-AB.
H7082-CA: Revision C with conformal-coated PCB assembly; rated for extended humidity and condensation environments.
H7082-D: High-reliability variant with MIL-grade capacitor selection; used in instrumentation and defense-adjacent installations.
H7082-DA: Revision D with updated crowbar protection circuit; prevents downstream board damage on output overvoltage events.
H7082-E: Extended input voltage range (90–264 VAC universal input); supports international 50/60 Hz grid installations.
H7082-EA: Revision E with dual-fuse input protection; field-replaceable fuse block for reduced maintenance downtime.
H7082-F: Fan-cooled variant for high-ambient installations; integrated thermal cutout at 70°C.
H7082-FA: Revision F with upgraded fan assembly; reduced acoustic signature for control room enclosure deployments.
H7082-G: Redundant output configuration; supports N+1 power supply architectures in critical uptime applications.
H7082-GA: Revision G with active load-sharing circuitry; balances current draw across parallel supply installations.
H7082-H: Final production revision; incorporates all prior ECO (Engineering Change Order) updates; highest field reliability rating in the H7082 family.

Sourcing Hard-to-Find & Obsolete H7082 Parts

DriveKNMS maintains a dedicated inventory program for end-of-life DEC power supply modules, including the full H7082 revision spectrum. Because DEC ceased manufacturing operations under the HP acquisition, no authorized new-production source exists for any H7082 variant. All available units in the global supply chain are either new-old-stock (NOS) pulled from decommissioned systems, or professionally refurbished units that have undergone full electrical restoration.

Quality Control for the H7082 Range

The H7082 series presents specific refurbishment challenges due to its age profile and the failure modes characteristic of switching power supplies manufactured in the 1970s–1990s. DriveKNMS applies a structured test protocol to every H7082 unit processed:

Capacitor ESR and capacitance verification: All electrolytic capacitors are tested for equivalent series resistance and capacitance value. Units with capacitors outside ±20% of rated capacitance or with ESR exceeding manufacturer limits are recapped using modern long-life equivalents rated for 105°C operation.
Output rail regulation accuracy: Each output rail (+5V, +12V, -12V) is measured under no-load, 50% load, and full-rated load conditions. Regulation must remain within ±2% of nominal across the full load range.
Ripple and noise measurement: Output ripple is measured at full load using a 20 MHz bandwidth oscilloscope. Ripple exceeding 50 mV peak-to-peak on the +5V rail or 100 mV on the ±12V rails results in unit rejection or further repair.
Overcurrent protection verification: Each unit is tested for OCP trip point accuracy. The protection circuit must activate within the specified current window without nuisance tripping under normal load transients.
Thermal cycling and burn-in: Units are operated at full rated load for a minimum of 24 hours in a controlled thermal environment to screen for infant mortality failures in recapped or repaired assemblies.
Backplane connector inspection: Edge connector contacts are inspected under magnification and cleaned or re-tensioned as required to ensure reliable backplane mating in BA-series enclosures.