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Recap guide

Recap the Compaq Portable

Old power supply caps and failing tantalums are standard on these. The Portable III has the best write-ups.

Open the interactive checklist Tick off each capacitor as you replace it. It saves in your browser.

Worth a recap. Reports say it is a common and useful fix on this machine.

Which board do I have?

Boards changed during production. These notes come from the linked sources, and many are only partly documented, so check the board in front of you.

  • Compaq Portable (original) (Medium confidence). How to tell: Original 1983 portable. Capacitors: Tantalum caps on motherboard and ISA cards are failure risks. Capacitor list differs from other revisions: not known. Source
  • Compaq Portable II (Medium confidence). How to tell: Intel 286 luggable. Capacitors: PSU C13, a 15uF 25V tantalum, has burnt in several units. Capacitor list differs from other revisions: not known. Source
  • Compaq Portable III (Medium confidence). How to tell: 286 plasma luggable sharing a PSU with the 386. Capacitors: PSU makes two 200V rails for the screen; tantalums near the PSU connector 15uF 25V and 10uF 15V fail. Capacitor list differs from other revisions: not known. Source

Where to start

Clues from write-ups and forum threads, not a diagnosis. Low confidence means one thread or one repair; high means several write-ups agree.

  • Shorting tantalums (High confidence). Several write-ups report shorted or burnt power supply tantalums. A VOGONS thread names positions on a Portable III (PSU, C47, C49, C2) and suggests higher-voltage replacements. Source
  • Check for a cracked trace (Low confidence). On one Portable III the power supply was mostly recapped but the real fault was a cracked trace, so check for that. Source
  • Original Portable list (Medium confidence). Old Crap has a capacitor chart for the original Portable, plus teardown photos and a Meanwell MPQ-200B power supply replacement. Source

Tips, tales and maybes

Found in write-ups and forum threads. These are other people's reports, not tested by us. Check part references and values against your own board.

  • Story: Portable 2 PSU with a 2Hz click (Medium confidence). A Compaq Portable 2 supply clicked at 2Hz with the PowerGood signal never asserting. The owner replaced Sprague 81D, Nippon RX and Sprague 672D/678D parts with 105C high-ripple types close to the originals in size, and replaced tantalums on the motherboard and video card with MLCCs. An ATX retrofit was also discussed. Source
  • Watch out: Portable II: C13 shorts and burns (Medium confidence). An Old Crap page on the Portable II says C13, a 15uF 25V tantalum between the regulator input and common, shorted and burned on multiple units. Other symptoms were the supply refusing to restart for about seven minutes, overheating regulators and no voltages without a load. Some owners used a PicoPSU with buck converters instead. Source
  • Tip: Beep and error code families (Low confidence). The original Portable page says POST error codes starting 6 indicate disk drive faults, 5 the video adapter and 1 the system board, and that the Zenith CRT flyback often fails. The Meanwell replacement needs a power-good signal buffered, with a 7409 gate suggested. Source
  • Watch out: Plasma rails on the PSU connector (Medium confidence). A Portable III page says the supply has a second connector carrying two 200V rails for the gas plasma screen, and recommends replacing all caps and testing the regulators before powering on. It also notes that only drive type 04 (about 70MB) worked reliably, and that Connor drives are unreliable. Source
  • Watch out: Factory reversed tantalums in the expansion unit (Medium confidence). A Portable III write-up reports shorted tantalums causing immediate shutdown and says the expansion unit had two tantalums fitted in reverse polarity at the factory, replaced with electrolytics. The Dallas chip battery fails with age and the author rewired it for an external cell. Source
  • Story: Swapped tantalum, failed again (Low confidence). A Portable III supply with an exploded tantalum (about 5uF 25V, partly readable) was fixed with a 6.8uF 35V part on the reasoning that a filter cap's exact value matters little there. It passed a smoke test but later failed again with the same burning smell. Source
  • Story: Humid storage, popped tantalums and NiCd crystals (Low confidence). A forum post on a stored Portable describes several 10uF 16V tantalums going pop plus exploded supply caps. A soldered 3.6V NiCd had covered the board in green crystals, cleaned with dilute vinegar then water. Source

Before you start

  • Boards changed during production. Check your board number against the guides before you order parts.
  • A mains power supply can hold a dangerous charge. If you are not trained to work on one, have a professional do it.

Guides we used

This page and the interactive bench are built from these. They have the photos and the full detail, so please read them and support their authors.

The capacitor list

We have not checked a capacitor list for this machine yet, so none is shown. Follow the guide above for your board, then add the capacitors in the interactive checklist and it builds a shopping list for you.

Skip the sourcing

While you are in there

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Steps, tools and safety

The steps, the tools in top, middle and budget picks, and the safety list are the same for every machine, so they live on one page: How to recap, step by step.

Values are shown as published in the guides above, and boards changed during production. Check the board in front of you. A recap involves hot tools and, on some machines, dangerous voltages. You do it at your own risk.

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