ABI avionics repairdefense electronics board repaircomponent-level fault locationcircuit board reverse engineering
Board-Level Repair and Reverse Engineering for Avionics and Defence Electronics
The OEM has ended support and the schematics are long gone, but the board has another ten years of service ahead. Component-level fault location, schematic recovery and counterfeit screening of spares, all without documentation.
In short
Avionics and defense circuit boards often stay in service for years after the OEM ends support. The repair shop has no schematic and no test program, only a failed board and a few known-good ones. ABI BoardMaster combines 64-channel fault location, advanced test and matrix scanning modules (expandable to 256 channels) that learn from a good board and compare a suspect board in real time, giving functional test without any knowledge of the circuit. SYSTEM 8 BFL performs in-circuit digital IC test, connection test and ±10 V V-I signature scanning without powering the whole board. RevEng captures connectivity from a bare board on 1024 to 2048 channels and produces a netlist and schematic as the basis for obsolescence management. SENTRY screens counterfeit ICs in the spares supply chain by 256-channel PinPrint electrical signature comparison. This article shows how these tools form a repair process that technicians of different experience can repeat.
Where repair starts when there is no documentation
Avionics and defense equipment routinely serves for twenty or thirty years. The components on the boards are long obsolete, the OEM no longer provides technical support, and the schematics and test programs delivered with the equipment have usually been lost through a few reorganizations. What the repair shop has left is a failed board, a few good boards that still work, and a procurement estimate of how long and how much a replacement board would take. A single board can run to thousands of dollars, if it can be bought at all.
The traditional approach relies on a senior technician measuring by experience and swapping parts one at a time. The result depends entirely on the individual and cannot be reproduced once that person moves on. Making repair a repeatable process takes three things: a functional test that grades a board without understanding the circuit, an in-circuit test that checks a single IC without powering the whole board, and a way to rebuild connectivity when documentation is missing. ABI's systems are designed around exactly these three.
Functional test without knowing the circuit: learn from a good board, then compare
BoardMaster is a combination of SYSTEM 8 modules: one 64-channel Board Fault Locator (BFL), one Advanced Test Module (ATM) and one Advanced Matrix Scanner (AMS), each expandable to 256 channels, plus an analog IC test module, the MIS4 multiple instrument station and a programmable power supply module, connected to a Windows PC over USB. MIS4 contains a digital oscilloscope, digital multimeter, arbitrary waveform generator and frequency/event counter, so the instruments normally scattered across a repair bench are controlled by one software package. The portable external-case version takes the same capability to the hangar or the field instead of sending boards back to the lab.
The core method is learn and compare. A test clip is placed on an IC on the good board, the system records the logic state, voltage and V-I signature of every pin, the same procedure is run on the suspect board, and a live comparison marks the pins whose behavior differs. None of this requires knowing what the IC does in the circuit, and no schematic is needed. Digital and analog V-I signatures can be displayed in 2D or 3D, so differences between boards are visible at a glance, and a short locator tool narrows a bus short down to a single component.
No need to power the whole board: in-circuit IC test and V-I signature scanning
Powering a failed board is itself a risk. It can destroy components that were still good, or make an intermittent fault disappear for a while. SYSTEM 8 BFL powers a single IC through the test clip and drives its inputs, running a functional test against truth tables in its library for TTL and CMOS devices in DIL, SOIC, PLCC and QFP packages. Drive capability is typically 80 mA H-L and 200 mA L-H, enough to overdrive surrounding circuitry in situ. Thresholds are adjustable in 100 mV steps, and an automatic mode finds the tightest threshold the device still passes, pulling marginal, degraded parts out of the barely-passing population.
With no power applied at all, the connection test (MDA) detects shorts, opens, floating inputs and connected pins; the V-I test sweeps programmably from -10 V to +10 V at a maximum test current of 1 mA and compares signature curves between good and suspect boards, and the thermal test shows a temperature indication per pin. ATM extends voltage drive and measurement to logic families including TTL, CMOS, LVTTL, ECL, PECL and LVPECL. Digital ICs that have already been removed go to the ChipMaster Compact Pro: a 40-pin ZIF socket, unknown-IC search and a loop test mode suited to catching intermittent faults.
Schematics from a bare board: RevEng and obsolescence management
Without a schematic there is no way to plan substitute parts, commission a remake, or hand the repair knowledge to the next engineer. RevEng connects to groups of components on the board through clips, connectors and probes and measures continuity with no power applied, with voltage and current limited during measurement to protect semiconductors. The cabinet system provides 1024 to 2048 measurement channels and can be expanded after installation. The software supports automatic clip location, optimized movement paths and repeat-learn verification, and learning can be done by area and paused or restarted at any time.
The output is a netlist of components and connections, from which the EdWin XP CAD suite produces a paged schematic with bus structure. The manufacturer states that a typical board can be drawn in one day, with a library of about 12,000 parts. ABI published the case of a defense and aerospace MRO organization that, after more than twenty years of using its products, formally adopted RevEng in 2017 to support long-term fleet maintenance; its engineers described the system as bringing circuit board troubleshooting to its final stage. For military and aerospace repair organizations in Taiwan, the same path applies to rebuilding obsolete boards in-house or through a contractor.
Counterfeit IC screening for the spares supply chain: SENTRY
Obsolete components can only be sourced from the secondary market or brokers, and counterfeit risk enters the spares inventory with them. Visual inspection and X-ray catch only part of the problem: remarked good parts, empty packages with no die or bond wires, and substitutes with the wrong pinout are often found only when the assembled board fails test. SENTRY screens by PinPrint electrical signature: it measures the V-I characteristic of every pin against the others, compares it with reference data built from known-genuine parts, and detects missing or wrong dies, missing bond wires, pinout mismatches and pin impedance differences.
The hardware provides 256 test channels and a maximum test voltage of 20 V peak-to-peak, with sine, ramp and triangle waveforms, covering packages from two-pin devices to BGA, with universal SOIC and PLCC adapters and custom designs available. Reference libraries are built and configured by the user, and analysis reports can be exported and shared along the supply chain, so acceptance and any later investigation rest on the same evidence. At 3.5 kg and 27 × 25 × 9 cm it sits at an incoming inspection station and needs no electronics background to operate.
The same result from technicians of different experience
Each of these measurements can be run on its own, but what a repair shop really needs is a fixed procedure: any technician given the same board tests in the same order and reaches the same verdict. The TestFlow manager in SYSTEM 8 Ultimate software chains the unpowered connection and V-I tests, the powered functional comparison, and the oscilloscope and multimeter measurements into an interactive sequence, each step carrying prompts and pass criteria. A graphical test generator lets senior engineers write custom test vectors into the procedure, and data logging keeps every result for trend analysis and quality audits.
Evencat is the authorized distributor for ABI Electronics in Taiwan. We help configure the SYSTEM 8 module set to the board types and channel counts involved, provide equipment calibration documentation and Chinese-language technical support, and help the repair shop build its learn data and test procedures from the first good board. SYSTEM 8 Ultimate software comes with free lifetime updates and multi-license installation, so when an existing site adds modules or channels later, its test procedures carry over unchanged.
Instruments for this job
SYSTEM 8 ATM
In-circuit IC test across multiple logic families, voltage drive and measurement
View specifications
ChipMaster Compact Pro
40-pin out-of-circuit digital IC test, loop mode for intermittent faults
View specifications
Manufacturer references
- New contract announcement — Defense and aerospace MRO organization adopts RevEng
- Case study: aerospace manufacturer adopts BoardMaster — Aerospace manufacturer tests and repairs avionics boards with BoardMaster
- ABI Electronics - Applications — Application overview (military, transport, industrial)
- ABI BoardMaster - Digital & Analogue In Circuit Functional Tester — Module composition, channel counts and software functions
- RevEng Schematic Learning System — Channel counts, learning method and EdWin XP output
- SENTRY Counterfeit IC Detector — PinPrint principle and hardware specifications
- SYSTEM 8 Board Fault Locator Data Sheet — Drive currents, thresholds, V-I sweep range
- SYSTEM 8 ATM - In-Circuit and Board Level Testing Solution — Supported logic families and test types
- ABI ChipMaster Compact Professional — 40-pin ZIF, unknown-IC search and loop test
Image credits: AMPTEC Research (Manufacturer material, used as authorized distributor); ABI Electronics (Manufacturer material, used as authorized distributor)
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