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4.1 Assembly order and first POST

Lesson
Hardware safety: isolate power; never open a PSU.

Before touching hardware

  • Follow the exact model's service instructions. Shut down, unplug mains and peripherals, and disconnect any internal battery as instructed. Sleep, the PSU switch, or unplugging a laptop charger alone does not fully isolate power.
  • Let parts cool. Use a clean, dry workspace and approved ESD precautions. Hold boards by their edges, avoid contacts, account for screws, and never force connectors.
  • Never open a PSU or insert tools through its vents; stored energy can remain after unplugging. Use only modular cables confirmed compatible with the exact PSU model.
  • Isolate power before every physical change or cleaning. Powered tests are software/external observations with hands and tools out. No live probing, unspecified pin bridging, or damaged-battery servicing.
  • Stop for damage, swelling, liquid, burning smells, or unclear instructions; consult qualified service. Photos, diagrams, and supplied readings are sufficient for these exercises.

Service and ESD guidance ยท Example PSU cable chart. Check your exact model.

Practice lab

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Saved on this device. Practice is ungraded.

Sequence

Plan first-startup checks for a newly assembled PC

A build technician has a compatible cooler mounted, a supported DIMM, board power, and correct standoffs documented. Order inspection, external POST observation, and any follow-up changes before OS acceptance. Exact service instructions, power isolation, and ESD procedures govern physical work.

Use the arrows to order the steps.

  1. Complete required protective closure, clear hands and tools, then reconnect power only as instructed for startup observation.
  2. Observe first POST and supplied debug indicators externally; record detected CPU/RAM, firmware and temperature without touching powered internals.
  3. Shut down and isolate power again before any physical addition, reseating, or cable change required by the plan.
  4. Make one supported isolated physical change, repeat the observation boundary, and record what changed before proceeding to OS/workload validation.
  5. With power and applicable battery isolated per manufacturer procedure, check documented fit, cooler, DIMM slots, standoffs, cables and loose screws.
Lesson notes

Assemble and test in stages so a failure remains close to the change that introduced it.

Stage the build

A common sequence is motherboard preparation, CPU, cooler, one memory kit, initial board power, storage, case installation, GPU, front-panel and USB headers, cable management, firmware settings, and operating system setup.

  • Check CPU and socket carefully before cooler pressure.
  • Use recommended memory slots.
  • Confirm debug LEDs or POST behavior before adding complexity.
  • Add devices in a way that keeps symptoms readable.

Firmware setup

After first POST, check BIOS version, memory profile, boot order, fan behavior, storage detection, and CPU temperature. Firmware settings are part of the build record.

Worked example

Inputs: Assembly simulation: cooler mounted, one supported DIMM, board power connected, screws accounted for.

Task: Describe the transition to first POST and back to a physical change.

Check the reasoning

Check manufacturer instructions; protect/close as required; remove hands/tools; reconnect power for observation; shut down and isolate again before adding/reseating parts.

Do not bridge unspecified pins, touch powered internals, or run a CPU without its correctly mounted cooler.