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Repair guide

Replace a dead vintage PC power supply with an ATX unit

Original AT and XT supplies are hard to find and often need serious work. Many owners swap the whole unit for a modern supply, or a compact unit like a Meanwell, and keep the original for display.

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Power · Careful · about 90 minutes. Worth doing. Reports say this fix helps on many machines.

You are in the right place if: The PC is dead or unstable, or the original supply smells, hums or has failed.

Before you start

  • Never open the old supply. Mains-side capacitors hold dangerous charge.
  • Check polarity on every connector before you power on.
  • If you are unsure, hire a repair person for the supply swap.

Board revisions and models

AT, XT, PS/2 and portable supplies differ in connectors and rails.

Parts you may need

  • ATX power supply or compact supply. Replacement Amazon · eBay
  • AT to ATX adapter harness. Connect to old connectors Amazon · eBay
  • Dummy load. Load for testing Amazon · eBay

Tools

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Step by step

  1. Unplug and open the PC Disconnect from mains and open the case.
  2. Label the cables Photograph the cabling and label each connector.
  3. Remove the old supply Unscrew and lift it out without opening it.
  4. Plan the replacement Choose a modern unit or an adapter harness suited to your machine.
  5. Check the voltages needed Check which rails your machine uses (including -5V and -12V) and whether your chosen supply provides them.
  6. Fit the new supply Mount it and connect the cables with the correct polarity.
  7. Add a load if needed Some supplies need a minimum load to start.
  8. Test off the machine first Test the supply on the bench with a load, checking voltages.
  9. Power up and monitor Power on the PC and watch for smoke, smells or noise.
  10. Keep the original Store the old supply safely.

Tips, tales and maybes

Found in write-ups and forum threads. These are other people's reports, not tested by us.

  • Story (Medium confidence). One XT supply rebuild warned about suppressor capacitors and ended by swapping in an ATX board. Source
  • Story (Medium confidence). A Compaq Portable write-up replaced the supply with a Meanwell MPQ-200B. Source
  • Story (Medium confidence). A 5150 revival thread found supply capacitor failures and advised replacing all similar capacitors at once. Source

Guides we used

We wrote the steps in our own words from these. They have the photos and the full detail, so please read them and support their authors.

Boards and models vary, so check what is in front of you. A repair can involve hot tools, chemicals and, on some machines, dangerous voltages. You do it at your own risk.

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