The Repair LibraryRead · Learn · Master

Mechanical Provocation — Flex, Tap, and Vibration

The mechanical intermittent is the one that follows motion: the laptop that blanks when its lid moves, the console that crashes when the desk is bumped, the car radio that cuts out on rough roads and behaves in the driveway. Behind it is almost always a connection at the edge of contact — a solder joint cracked by years of thermal cycling or one hard drop, a pad lifting from its laminate, a connector whose spring contacts have relaxed, a wire strand broken inside intact insulation — and it fails exactly when flex, tap, or vibration moves the crack. This section arms the campaign's second provocation: summoning that fault with deliberate, controlled motion instead of waiting for the next bump. The wiggle test from physical inspection grows into a method — the whole device handled and repositioned first, the way transport and use would move it, then zones of the board pressed through an insulated tool, then single joints and pins prodded one at a time, every round with an instrumented observable armed, because a dropout that nobody captured teaches nothing. Direction matters and the section teaches why: a crack opens under one bend and closes under the opposite one, so a joint that responds to pressure from the north and not the south is describing its own geometry. Around the technique sits the discipline that keeps force diagnostic instead of destructive: insulated tools that cannot short what they touch, graded pressure that starts featherweight, flex measured in millimetres — because ceramic capacitors crack under enthusiastic bending and the test must never create the faults it hunts — and respect for live boards under moving hands. And as with every provocation, the recipe closes the loop: the response is confirmed by repetition and reversal, the suspect is verified under magnification, and the repair is proven when the same flex, tap, and handling that once summoned the fault reliably summons nothing. By the end, the fault that follows motion performs on your schedule, names its own joint, and stays fixed.

IntermediateMedium Risk22 min read

What You Will Learn

  • You will learn to read a fault history for its mechanical window — the motions, positions, and impacts that summon it.
  • You will learn to summon a mechanical intermittent with controlled handling, flex, tap, and cable manipulation, observable armed.
  • You will learn to narrow a responding fault from the device to a zone to a single joint, using direction of pressure as evidence.
  • You will learn to apply force that stays diagnostic — insulated tools, graded pressure, and millimetre flex that cannot create faults.
  • You will learn to confirm the suspect and prove the repair by re-running the mechanical recipe until it reliably summons nothing.

What You Will Be Able To Do

  • You will be able to read a fault history for its mechanical window — the motions, positions, and impacts that summon it.
  • You will be able to summon a mechanical intermittent with controlled handling, flex, tap, and cable manipulation, observable armed.
  • You will be able to narrow a responding fault from the device to a zone to a single joint, using direction of pressure as evidence.
  • You will be able to apply force that stays diagnostic — insulated tools, graded pressure, and millimetre flex that cannot create faults.
  • You will be able to confirm the suspect and prove the repair by re-running the mechanical recipe until it reliably summons nothing.

Required Tools

  • An insulated prodding tool — a chopstick, nylon spudger, or plastic probe
  • A soft-faced tapping tool, such as a screwdriver handle or eraser end
  • A scope or logger to arm as the observable during every mechanical run
  • Magnification to inspect responding joints and connectors
  • A notebook for mechanical windows, responses, and recipe results

Section Overview

The mechanical intermittent follows motion, and this section summons it with deliberate, controlled motion — the campaign's second provocation (why-intermittents-are-the-hardest-faults). The suspects are connections at the edge of contact. Cracked solder joints on heavy or stressed parts, lifting pads, relaxed connector contacts, and wire strands broken inside intact insulation all make and lose contact as flex, tap, and vibration move the crack. The history names the motion. A fault that tracks handling, transport, position, cable movement, or impact is describing its own summons, and the recipe recreates exactly that motion first (mechanical-and-connector-inspection). The provocation escalates from device to joint. Mechanical provocation starts with whole-device handling and repositioning, narrows to zone presses through an insulated tool, and finishes with the tap test and point prodding of single joints and pins — every round under an armed observable, because an uncaptured dropout teaches nothing (capturing-transients-and-single-shot-events). Direction is evidence. A crack opens under one bend and closes under the opposite, so the flex test reads not just where the board responds but which way — geometry that points at the guilty joint. Force stays diagnostic. Insulated tools, graded pressure from featherweight up, and flex in millimetres keep the test from creating the faults it hunts — ceramic parts crack under enthusiastic bending. And the recipe proves the repair. The same handling, flex, and tap that summoned the fault re-runs against the fix until it reliably summons nothing (thermal-provocation-forcing-heat-and-cold-dependent-faults). Read the motion, escalate the touch, weigh the direction, grade the force, and prove by the same motions — and the fault that follows movement performs on schedule.

Why This Matters

Mechanical intermittents are everywhere aging electronics live — every drop, every thermal cycle, and every insertion works some joint toward its crack — and they are the class most often solved by feel and luck instead of method (why-intermittents-are-the-hardest-faults). This matters because the motion is summonable in seconds: a fault that waits weeks for the right bump appears in the first minute of a systematic flex-and-tap walk, making this the fastest provocation in the campaign. This matters because the localisation comes free: thermal summonses need narrowing rounds, but a point prod that drops the signal has already named a joint — touch is inherently local (mechanical-and-connector-inspection). It matters because unwitnessed responses evaporate: a flicker seen from the corner of the eye during a prod cannot be distinguished from imagination, while a tripwire capture of the same dropout is evidence with a timestamp (capturing-transients-and-single-shot-events). It matters because careless force manufactures faults: a board flexed in centimetres cracks ceramic capacitors and lifts pads, converting a one-fault device into a three-fault device and the test into vandalism. And it matters because unproven mechanical repairs bounce: a resoldered joint that was never re-flexed, re-tapped, and re-handled ships with its verdict untested, and the next bump sends it back (thermal-provocation-forcing-heat-and-cold-dependent-faults). Master controlled motion, and the most common intermittent class becomes minutes of method instead of weeks of luck.

Required Prerequisites

  • Why Intermittents Are the Hardest Faults — Section 9.1 built the failure window, the reproduction recipe, and the instrumented observable; this section executes them for the mechanical class.
  • Mechanical and Connector Inspection — Section 2.4 introduced the wiggle test and the mechanical suspects — connectors, joints, strain points; this section grows that inspection move into a full summoning method with instruments watching.
  • An insulated prod — chopstick, nylon spudger, or plastic probe — to press zones and joints without shorting anything (mechanical-and-connector-inspection)
  • A notebook or worksheet — to record motions tried, responses, directions, and the shrinking recipe
  • A soft tapping tool — a screwdriver handle or eraser end — to deliver small, repeatable impacts
  • Isopropyl alcohol and swabs — to clean suspect connector contacts once the narrowing names them
  • Labels or tape flags — to mark responding zones and joints for inspection under magnification
  • A device with a known mechanical intermittent — to practise the full summon-narrow-prove cycle (why-intermittents-are-the-hardest-faults)
  • A scope with single mode and persistence, or a logging meter — to arm as the observable through every mechanical run (capturing-transients-and-single-shot-events)
  • A scrap board on a bench supply — to practise graded pressure and millimetre flex where mistakes cost nothing
  • A cable or harness with a known internal break — to feel how a broken strand responds to manipulation along its length
  • Magnification — loupe or microscope — to confirm responding joints visually before repair (mechanical-and-connector-inspection)
  • A notebook of mechanical recipes — to build the handling patterns that summon faults, per device family

Real-World Applications

Controlled motion closes the complaints that arrive with the word "sometimes". A technician with a laptop that blanks when the lid moves arms persistence on the display feed and works the hinge slowly through its travel — the ghost appears at one angle, and the harness at the hinge becomes the suspect (capturing-transients-and-single-shot-events). A repairer holding a console that crashes when bumped recreates the bump with a soft tap walk across the board and watches the tripwire fire only when the taps reach one corner — the zone with the heavy inductor (why-intermittents-are-the-hardest-faults). Someone narrowing inside a responding zone prods joint by joint with a chopstick and finds the one pin that drops the rail at featherweight pressure — then confirms it by pressing from the other side and feeling the fault refuse, the crack's geometry showing itself (mechanical-and-connector-inspection). A technician with a cable that "sometimes charges" flexes it inch by inch under a logging meter and finds the broken strand at the strain relief, not the connector everyone blamed. And a bench proving a resoldered joint re-runs the whole mechanical recipe — handling, flex, tap, the works — and files ten silent runs as the verification (thermal-provocation-forcing-heat-and-cold-dependent-faults). The failures this prevents: weeks waiting for a bump the bench could deliver in seconds, a real flicker dismissed for want of a witness, ceramic capacitors cracked by enthusiastic flexing, and a resoldered board returned by the next pothole.

Common Challenges

  • The response is fleeting and easy to doubt. A prod produces a millisecond dropout, not a steady fault — the difficulty is that only an armed tripwire or persistence watch turns that flicker into evidence, so the instrument discipline must hold on every single press (capturing-transients-and-single-shot-events).
  • Everything moves everything. Pressing one corner flexes the whole board, so early responses are ambiguous about location — the difficulty is escalating patiently from device to zone to joint instead of trusting the first response's address.
  • The test can create what it hunts. Ceramic parts crack and pads lift under excessive force — the difficulty is keeping pressure graded and flex in millimetres when frustration argues for more (mechanical-and-connector-inspection).

Safety Notes

Risk Level: Medium. Mechanical provocation puts moving hands and tools on powered boards — the standing live-work discipline plus the specific risks of force near live circuits.

Professional Tips Before Starting

  • Recreate the owner's motion first. The history's bump, lid, cable, or pothole is the proven summons — start with that exact motion before inventing your own (why-intermittents-are-the-hardest-faults).
  • Arm before you touch. The response to the very first press may be the only one you get — the tripwire or persistence watch goes live before any hand reaches the board (capturing-transients-and-single-shot-events).
  • Note the direction of every response. A crack opens one way and closes the other — "drops when pressed from the north, holds from the south" is geometry naming a joint.

The Mechanical Summons — Handle, Flex, Tap, and Prove

Recap and Frame

Section 9.1 classified the intermittent that follows motion; this section summons it, and the tools are hands, insulated sticks, and patience — under instruments (why-intermittents-are-the-hardest-faults). The suspects are known from inspection. Physical inspection taught the mechanical rogues' gallery — cracked joints on heavy and stressed parts, connector contacts gone soft, strain-point wire breaks, lifting pads — and taught the wiggle test as the way to interrogate them (mechanical-and-connector-inspection). This section scales the wiggle test into a method. One inspection move becomes a campaign: whole-device handling first, then zone presses, then joint-by-joint prodding, each round recorded and each response confirmed. The observable does the witnessing. Mechanical responses are milliseconds long, so every run happens under a tripwire, persistence, or a logger armed before the first touch — the flicker becomes a capture with a timestamp (capturing-transients-and-single-shot-events). The escalation mirrors the thermal campaign. Global summons, narrowing rounds, confirmation by repetition and reversal, and verification by the same recipe — the pattern from thermal provocation repeats with motion in place of temperature (thermal-provocation-forcing-heat-and-cold-dependent-faults). And force has a ceiling. The test must never create the faults it hunts, so pressure grades up from featherweight and flex lives in millimetres. Hold the frame — known suspects, a scaled-up wiggle test, witnessed milliseconds, the campaign's escalation, and graded force — and motion becomes the fastest summons in the chapter.

The Mechanical Window — Reading Motion from the History

The mechanical window is written in verbs — bumped, moved, carried, plugged, opened — and the history hands them over to anyone who asks (why-intermittents-are-the-hardest-faults). Impacts point at joints. A fault that follows bumps, knocks, and transport points at cracked solder — heavy components, connectors, and board-edge parts whose joints carry the most mechanical stress and crack first. Position points at gravity's load. A device that fails standing up but not lying flat, or only after being moved to a new spot, is describing a crack that gravity opens in one orientation and closes in another — though loose conductive debris shifting with orientation can mimic the same pattern, which is what the prerequisite inspection exists to catch before anything is powered inverted. Cable motion points at terminations. A fault that tracks plugging, unplugging, or moving a cable points along that cable's path — the connector contacts at either end and the strain reliefs where strands break inside intact insulation (mechanical-and-connector-inspection). Lids and hinges point at harnesses. A fault that follows opening, closing, or adjusting points at the wiring that crosses the moving joint, flexed thousands of times and failing one strand at a time. Combination windows are common. Warm plus flexed is a frequent pairing — the crack that only opens when expansion has already widened it — so a mechanical summons that stays quiet on a cold device may need the thermal soak first (thermal-provocation-forcing-heat-and-cold-dependent-faults). Impacts to joints, position to gravity, cables to terminations, hinges to harnesses, and combinations noted — and the mechanical window is read. Let the history's verbs choose where the hands go first.

The Summons — Handling, Flex, Tap, and Cable Work

The global summons recreates the motion the history names, whole-device first, because the fault's address is still unknown (why-intermittents-are-the-hardest-faults). Handling comes first. The device is lifted, turned, set down, and repositioned the way its owner and its transport would — the gentlest summons and the closest to the field, run with the observable armed before the first touch (capturing-transients-and-single-shot-events). The tap walk covers the board. Small, repeatable impacts from a soft tool — an eraser end, a screwdriver handle — walk across the assembly in a grid, each tap a question and the tripwire listening for the answer. The flex is gentle and global. With the board supported, gentle twisting and bending pressure — millimetres of travel, applied at edges and mounting points — works the assembly the way temperature cycles and carrying do. Cables and connectors get their own pass. Each cable is flexed along its length inch by inch, each connector wiggled in each axis and each plug reseated deliberately, because terminations and strain points are the mechanical class's most common address (mechanical-and-connector-inspection). Orientation rounds catch gravity's faults. The device runs through its positions — flat, standing, inverted — with pauses at each, catching the crack that only gravity's direction opens. And every response is logged with its motion. What was moving, where, and which way when the observable fired — that trio is the raw material the narrowing will spend. Handle, tap-walk, flex, work the cables, rotate, and log each response with its motion — and the mechanical fault answers on schedule. Recreate the history's motion with the instruments listening, and the summons rarely takes ten minutes.

The Narrowing — Zone, Joint, and the Direction of the Crack

Once the fault answers, touch becomes the localiser — and touch is inherently local, so the walk from zone to joint is short (mechanical-and-connector-inspection). Zones are pressed through insulation. A fingertip's worth of pressure through an insulated prod lands on one palm-sized region at a time, and the zone whose press summons the fault while its neighbours stay quiet holds the suspect. Joints are prodded one at a time. Inside the responding zone, the prod's tip presses individual components, pins, and connector bodies at featherweight force — and the single point whose touch drops the signal has named itself (capturing-transients-and-single-shot-events). Direction is read as evidence. A crack opens under one bend and closes under the opposite one, so pressure from each side of a suspect is compared: the joint that responds from the north and holds from the south is showing the crack's geometry, and a response that reverses with direction is a stronger indictment than one that merely repeats. Repetition confirms before conclusions. A single flicker could be coincidence, so the responding motion is repeated — press, release, press — until the response tracks the touch reliably, the mechanical equivalent of the thermal campaign's reversal rounds (thermal-provocation-forcing-heat-and-cold-dependent-faults). Magnification closes the identification. The named joint goes under the loupe or microscope, where the crack, the lifted pad, or the relaxed contact is usually visible once you know exactly where to look — the provocation tells the magnifier where. Zones through insulation, joints at featherweight, direction read as geometry, responses repeated into reliability, and the suspect confirmed under glass — and the narrowing ends at a named joint. Let the touch walk from region to point, and the fault's address comes free with the summons.

The Discipline — Force That Stays Diagnostic

Mechanical provocation is the provocation most able to damage what it tests, so its discipline is about the ceiling on force (mechanical-and-connector-inspection). The tool is always insulated. Metal tools slip, and a slipped metal tip bridges live pins — the chopstick, nylon spudger, and plastic probe exist so that a slip cannot bridge anything: electrically, the worst it can do is nothing. Pressure grades from featherweight. Every press starts at grams and increases only in small steps, because a fault at the edge of contact responds to tiny forces — and a response found at featherweight is better evidence than one extracted by leaning in. Flex lives in millimetres. Boards are bent barely enough to work a crack — millimetres of travel at the edges — because ceramic capacitors crack, pads lift, and traces fracture under centimetre-scale enthusiasm, converting the test into the fault. Some zones are off-limits to force. BGA neighbourhoods, already-suspect pads, and anything primary-side get inspection and the gentlest handling only — the cost of a created fault there exceeds any diagnostic gain. A created fault announces itself as a new response. A response that appears mid-session where earlier identical presses were quiet is treated as possible damage, not discovery — the session pauses and the area goes under magnification before anything else is believed (why-intermittents-are-the-hardest-faults). Insulated always, graded from grams, millimetres of flex, no-force zones respected, and new mid-session responses treated as warnings — and force stays diagnostic. Summon with the least motion that works, and the board ends the test no worse than it began.

The Proof — Confirming the Suspect and Verifying the Repair

A named joint is a hypothesis until confirmed, and a repaired one is unproven until the motion that summoned the fault fails to (why-intermittents-are-the-hardest-faults). The suspect is confirmed three ways. The point response repeats reliably under the prod, the magnifier shows the crack or the relaxed contact, and — where the geometry allows — the direction test agrees: open from one side, closed from the other (mechanical-and-connector-inspection). The electrical capture completes the case. The observable's record — the dropout on the rail, the glitch on the line, timestamped against the press — ties the mechanical response to the electrical symptom the owner reported, closing the loop from complaint to joint (capturing-transients-and-single-shot-events). The repair addresses the mechanism. A cracked joint is reflowed or resoldered, a relaxed connector is cleaned and retensioned or replaced, a broken strand is cut back to good wire — the fix matches what the magnifier actually showed, not what the first guess assumed. Verification re-runs the whole recipe. The same handling, the same tap walk, the same flex and cable work — especially the exact motion and direction that summoned the fault — runs against the repair, repeated past the fault's old reliability, with the observable armed and the run count recorded (thermal-provocation-forcing-heat-and-cold-dependent-faults). The neighbours get a pass too. A joint that cracked has siblings under the same stress, so the verification includes a brief press of the surrounding joints — the second crack is cheapest to find now. Confirmed by repetition, glass, and direction; tied to the symptom by the capture; repaired to the mechanism; verified by the same motions past the old rate; with the neighbours checked — and the mechanical case closes. Prove the repair with the motion that proved the fault, and the next bump finds nothing.

Common Mistakes

  • Prodding with a metal tool. A slipped metal tip bridges live pins and creates the failure it was hunting — insulated prods only: chopstick, nylon, plastic (mechanical-and-connector-inspection).
  • Pressing before arming. The first press may get the only response of the session, and unwitnessed flickers prove nothing — tripwire, persistence, or logger goes live before any hand touches the board (capturing-transients-and-single-shot-events).
  • Flexing in centimetres. Enthusiastic bending cracks ceramic capacitors and lifts pads, manufacturing faults — millimetres of travel, graded from featherweight.
  • Trusting the first response's address. Early presses flex the whole board, so the first response is ambiguous — escalate device to zone to joint before naming anyone.
  • Skipping the mechanical re-test after repair. A resoldered joint never re-flexed ships unverified — re-run the full recipe, especially the exact motion that summoned the fault, past its old rate (why-intermittents-are-the-hardest-faults).

Troubleshooting Guidance

The mechanical campaign runs window, summons, narrowing, discipline, proof. If the history's verbs are bump, carry, or knock: tap-walk the board and handle the device whole, observable armed first (capturing-transients-and-single-shot-events). If the fault tracks position: run orientation rounds — flat, standing, inverted — with pauses, and let gravity work the crack. If it tracks a cable or a lid: flex the cable inch by inch and work the hinge through its travel, watching the harness and terminations (mechanical-and-connector-inspection). If the mechanical summons stays quiet: check for a combination window — soak the device warm first, then repeat the motion rounds, because many cracks open only when expansion has widened them (thermal-provocation-forcing-heat-and-cold-dependent-faults). If a zone responds: narrow inside it joint by joint at featherweight, and read the direction of every response as geometry. If a response appears where earlier identical presses were quiet: stop — treat it as possible created damage and put the area under magnification before believing anything. If the prod names a joint: confirm it — repetition, magnification, direction — and capture the electrical symptom against the press before repairing. If the repair is in: re-run the entire recipe including the summoning motion and direction, past the fault's old rate, and press the neighbouring joints while you are there (why-intermittents-are-the-hardest-faults). The throughline: let the history's verbs aim the hands, witness every touch, narrow by geometry, keep force in grams and millimetres, and prove the fix with the motion that proved the fault.

Verification & Testing Methods

Confirm the mechanical campaign was method, not massage:

  • [ ] I read the mechanical window from the history's verbs — impacts to joints, position to gravity, cables to terminations, hinges to harnesses — and started the summons with the exact motion the history named.
  • [ ] I ran mechanical provocation as an escalation — whole-device handling, the tap test walked in a grid, gentle global flex, cable and connector passes, orientation rounds — with the observable armed before the first touch and every response logged with its motion.
  • [ ] I narrowed by touch — zones through an insulated prod, then joints at featherweight — and used the flex test's direction as evidence, expecting a genuine crack to respond from one side and hold from the other.
  • [ ] I kept force diagnostic: insulated tools only, pressure graded from grams, flex in millimetres, no-force zones respected, and any new mid-session response treated as possible created damage and inspected before being believed.
  • [ ] I confirmed the suspect by repetition, magnification, and direction; tied it to the symptom with the observable's capture; and proved the repair by re-running the same recipe — including the summoning motion — past the fault's old rate, with the neighbouring joints pressed as well.

Then try the practice exercises below — hands-on mechanical work; scenarios differ from the quiz.

Practice Exercises

  1. Read the window, then tap-walk with a witness (5 minutes, hands-on). From the device's fault history — real or given — state the mechanical window first: which motions, positions, or impacts the history's verbs name, and where that aims the first round; then, on a powered practice board with a logger or tripwire armed, walk a soft-tool tap grid across the assembly and practise logging each tap's location against the record — proving to yourself the witness catches what the eye misses (capturing-transients-and-single-shot-events).
  2. Grade your own force (5 minutes, hands-on). On a scrap board, practise the pressure ladder with an insulated prod — featherweight, light, firm — and gentle millimetre flex at the edges, calibrating what each grade feels like before it ever lands on a customer's board (mechanical-and-connector-inspection).
  3. Find the strand in the cable (5 minutes, hands-on). Under a logging meter or scope, flex a known-bad (or deliberately nicked scrap) low-voltage cable — USB or similar, never a mains lead — inch by inch along its length and at both strain reliefs, and practise reading the record to name the break's location and the motion that opens it.
  4. Confirm, then write and run the proof (3 minutes, hands-on). For a real or simulated responding joint, first confirm it the way the section teaches — repeat the press, compare direction, and put it under magnification; then write the verification recipe — the summoning motion and direction, the run count that beats its old reliability, the neighbour presses — and run it against a healthy board to rehearse the pass that a repair would need (why-intermittents-are-the-hardest-faults).

These core steps — reading the motion window, the witnessed summons, narrowing by touch and direction, graded force, and proof by the same motions — are tested in the Chapter Quiz at the end of this chapter, where a score of 80% is required to continue.

Key Takeaways

  • The mechanical window is written in the history's verbs — impacts point at cracked joints on heavy and stressed parts, position at gravity-worked cracks, cable motion at terminations and strain reliefs, hinges at harnesses — and combination windows (warm plus flexed) are common (why-intermittents-are-the-hardest-faults).
  • Mechanical provocation escalates from whole-device handling through a soft-tool tap test grid, gentle global flex, cable and orientation rounds, to joint-by-joint prodding — with the observable armed before the first touch, because responses are milliseconds long (capturing-transients-and-single-shot-events).
  • Touch is inherently local, so the narrowing is short: zones through an insulated prod, joints at featherweight, and the direction of the flex test read as geometry — a crack opens from one side and holds from the other, and a direction-reversing response is the strongest indictment (mechanical-and-connector-inspection).
  • Force stays diagnostic by discipline: insulated tools only, pressure graded from grams, flex in millimetres never centimetres, no-force zones around BGAs and the primary side, and any new mid-session response treated as possible created damage.
  • The case closes on proof: the suspect confirmed by repetition, magnification, and direction; the electrical capture tying press to symptom; and the repair verified by the same recipe — the summoning motion included — past the fault's old rate, with the neighbouring joints pressed too (thermal-provocation-forcing-heat-and-cold-dependent-faults).

Skills Learned

  • You can now read a fault history for its mechanical window — the motions, positions, and impacts that summon it.
  • You can now summon a mechanical intermittent with controlled handling, flex, tap, and cable manipulation, observable armed.
  • You can now narrow a responding fault from the device to a zone to a single joint, using direction of pressure as evidence.
  • You can now apply force that stays diagnostic — insulated tools, graded pressure, and millimetre flex that cannot create faults.
  • You can now confirm the suspect and prove the repair by re-running the mechanical recipe until it reliably summons nothing.

Glossary Additions

  • mechanical provocation — summoning a motion-dependent intermittent with deliberate, controlled movement instead of waiting for the next bump: whole-device handling and repositioning first, then a tap walk across the board, gentle global flex, cable and connector passes, and orientation rounds, narrowing to zone presses and joint-by-joint prodding through an insulated tool. Every round runs under an armed instrumented observable — a tripwire trigger, persistence watch, or logger — because mechanical responses last milliseconds and an uncaptured flicker proves nothing. The discipline caps the force: insulated tools only, pressure graded from featherweight, flex in millimetres, and no-force zones around fragile and primary-side areas, so the test summons existing faults without creating new ones.
  • tap test — delivering small, repeatable impacts from a soft-faced tool — an eraser end or screwdriver handle — walked in a grid across a powered assembly while an instrumented observable listens, so a fault that answers to knocks and bumps reveals which region it lives in. Each tap is a question: the zone whose taps summon the fault while its neighbours stay quiet holds the suspect, and the tap test therefore serves as the mechanical campaign's coarse localiser, run after whole-device handling and before joint-by-joint prodding. Its impacts stay small and consistent — the test recreates the owner's bump in miniature, not the drop that caused the damage.
  • flex test — applying gentle, millimetre-scale bending or twisting pressure to a board or pressing a suspect joint from controlled directions, to work a crack open and closed while an instrument watches for the response. Direction is the flex test's special evidence: a crack opens under one bend and closes under the opposite, so a joint that responds to pressure from one side and holds from the other is displaying the crack's geometry — a stronger indictment than a response that merely repeats. Force stays strictly bounded — millimetres of travel, graded from featherweight — because centimetre-scale flexing cracks ceramic capacitors and lifts pads, creating the faults the test exists to find.

Suggested Next Sections

Must read next:

Recommended: