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PSU Rebuild

2026-02-21

Overview

The original power supply in the Compaq Portable 486c is a common failure point. Aging electrolytic capacitors dry out and lose capacitance, leading to voltage droop, ripple, and eventually failure to start. A full recap restores the PSU to reliable operation.

Recap

The PSU board was removed from its enclosure and all electrolytic capacitors were replaced. The board was cleaned of any electrolyte residue before installing the new caps.

PSU board removed and recapped on the workbench

Voltage Verification

After recapping, the PSU was tested with a multimeter to verify clean output on all rails before reconnecting to the motherboard.

12V rail — Reading 12.11V, well within spec.

Multimeter reading 12.11V on the 12V rail

5V rail — Reading 5.085V, well within spec.

Multimeter reading 5.085V on the 5V rail

Reassembly

The rebuilt PSU board reinstalled in its metal enclosure, ready to go back into the case.

Rebuilt PSU reassembled in its enclosure

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