RetroTechCollection

Psion Series 3mx Hinge Repair

Hinge repair for the Psion Series 3mx (1998).

The 3mx uses the same four-hinge clamshell as the rest of the family. The one thing that is different — and it will bite you — is the pair of SSD door microswitches you must protect on the way in.

The 3mx uses the same case and the same four hinges as the Series 3, 3a and 3c. The full procedure — hinge locations, both failure modes, the epoxy repair, the complete teardown, lid separation and reassembly — is on the Psion Series 3a Hinge Repair page and applies here unchanged.

This page records the 3mx differences.

⚠️ Open both SSD doors before lifting the mainboard

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On a 3mx this is not just good practice — it is the difference between a working machine and a broken one.

The 3mx senses its SSD slot doors with a pair of microswitches set at an angle. Prising the motherboard out with the doors closed snaps the plastic tips off those switches, after which the machine reports "not ready" and will not recognise a pack in either slot.[1]

If you are opening a 3mx to repair a hinge, you are going to lift the mainboard. Open both doors first.

While the board is out, inspect both switch tips — if a previous owner has been inside the machine, they may already be broken, and you have the machine apart anyway. The repair is on the Psion Series 3mx Troubleshooting Guide.

The four hinges

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Two visible hinges beyond either end of the button bar, with a metal rod down the centre; two hidden plastic nipples between the battery compartment and the button bar. The visible hinge shears at its 8 mm neck, usually from over-opening the lid; the hidden nipple breaks off, leaving the back edge crooked and the button bar flexing out. Both repair with epoxy, optionally reinforced with a thin steel strip.[2]

Donor lids

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The 3mx uses the same 480 × 160 panel as the 3a and 3c, so those lids fit physically.[3]

Three cautions:

  • A Series 3 lid will not work. That machine has a 240 × 80 panel and a different ribbon.[3]
  • Every 3mx is backlit, where most 3a and 3c lids are not.[4] Fitting a non-backlit donor lid will lose you the backlight.
  • The 3mx is matte silver; the 3c is dark grey and the 3a is a different shade again.[4] A donor lid will work, but it will not match.

No sticky coating

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Unlike the 3c, the 3mx has a painted matte silver finish rather than a rubberised soft-touch coating, so it does not develop the 3c's tacky case.[4]

The practical implication for this job: do not clean a 3mx case with isopropyl alcohol. The method that rescues a 3c will attack a painted finish.

Everything else

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Follow Psion Series 3a Hinge Repair for the teardown, the button bar and its springs, the LCD ribbon, the hinge pin extraction, the pre-reassembly power-up test and the reassembly sequence.

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References

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  1. ↑ Richard Zealley, "Psion Series 3mx SSD door microswitch repair", Retro Coding, 25 May 2020. Source for the microswitch arrangement, the damage mechanism, the resulting symptom and the requirement to repair both switches.
  2. ↑ David MacKay, "Psion 3a Hinge breakages". Source for the hinge locations, both failure modes, the over-opening cause and the epoxy repair.
  3. ↑ 3.0 3.1 "Psion specifications", netogram.com. Source for the shared 480 × 160 screen across the 3a, 3c and 3mx, and the Series 3's different 240 × 80 panel.
  4. ↑ 4.0 4.1 4.2 "Psion Series 3", Wikipedia. Source for the universal backlight on the 3mx, its late and largely US availability on the 3c, and the matte silver finish.


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