RetroTechCollection

Psion Series 3 General Maintenance

Preventive maintenance for the Psion Series 3 (1991).

A Series 3. The case, hinges, button bar and battery arrangement are shared with the 3a, 3c and 3mx, so most maintenance is common to all four.

The Series 3 shares its case, hinges, button bar, keyboard construction and battery arrangement with the 3a, 3c and 3mx. The full common procedure is in the Psion Series 3a General Maintenance guide — this page covers what is specific to the original Series 3.

⚠️ Safety

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No mains voltages. Two AA cells, and a +16 V Vh rail that appears at the SSD slots only when writing or formatting a Flash pack.[1] Everything is CMOS; use an anti-static strap.

What is specific to the Series 3

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Timekeeping: take the clock seriously

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This is the one maintenance difference that really matters.

The Series 3 has no hardware real-time clock. It keeps time by waking the CPU periodically — roughly every eight hours — to update the count. If the CPU cannot start because the main batteries are absent, the time is simply lost.[1]

So on a Series 3, unlike a 3a:

  • Do not store the machine with the AA cells out and expect the clock to survive.
  • Change the AA cells promptly rather than leaving the machine running on backup.
  • Expect to reset the clock after any extended storage, and check it after every battery change.

Backup cell

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The Series 3 takes a CR1620 lithium coin cell, as do the 3a and 3c. Replace it on a schedule rather than on failure — it is what holds your data during an AA change.[2]

Display

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The Series 3 screen is 240 × 80, black and white only — no grey plane and no backlight.[3] It is a physically different panel from the 3a's and uses a different ribbon, so a 3a lid will not simply transplant onto a Series 3. Bear that in mind before buying a donor.

Sound

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A piezoelectric buzzer driven directly from ASIC2, at high or low volume, and either by toggling a register bit or from the ASIC1 timer overflow.[1] There is no microphone and no sound recording — those arrived with the 3a. A Series 3 that will not record audio is not faulty.

Serial

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9600 baud through the optional link pod, with the comms software held in the pod's own ROM rather than in the machine.[3][2] A Series 3 that has "lost" its comms software has usually just lost its pod.

Everything else

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For the shared items — the battery lead, opening and closing the lid, the button bar, the SSD slots, the keyboard membrane, case cleaning and why the Series 3 family is not a recap candidate — see Psion Series 3a General Maintenance.

The single highest-value habit on any Series 3: open the lid squarely with two hands and stop at a comfortable angle. Over-opening is what shears the visible hinges.[4]

Preventive maintenance checklist

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  1. Back up to an SSD or a PC.
  2. Note the time before, and reset it after, any battery work — this machine will lose it.
  3. Remove the AA cells for storage; check the compartment for corrosion.
  4. Replace the CR1620 if you do not know its age.
  5. Inspect the battery lead where it flexes, and re-seat the two-pin connector.
  6. Check all four hinges for cracks.
  7. Confirm the button bar sits flush and responds.
  8. Clean both SSD slots and confirm packs are recognised.
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References

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  1. ↑ 1.0 1.1 1.2 Psion PLC, SIBO Hardware Reference, version 2.10, 3 February 1995, in the Psion Documentation Project. Source for the supply rails, the +16 V Flash programming rail, the timekeeping mechanism, the NMI sources and the power states.
  2. ↑ 2.0 2.1 "Psion Series 3", Wikipedia. Source for the backup cell types across the range and the documented clamshell problems.
  3. ↑ 3.0 3.1 "Psion specifications", netogram.com. Source for the Series 3 screen dimensions and video memory access mode.
  4. ↑ David MacKay, "Psion 3a Hinge breakages". Source for the over-opening failure mechanism.


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