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Psion Series 3mx General Maintenance

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Psion Series 3mx
Psion Series 3mx

The Psion Series 3mx (1998) uses the same style of case, hinges, button bar, keyboard and AA battery arrangement as the Psion Series 3a and Psion Series 3c.[1] The maintenance common to the family, including Psion's disassembly procedure and the battery lead, is in Psion Series 3a General Maintenance. The 3mx differs in its SSD door microswitches, its backup cell and its power rating.

Opening the case: SSD door microswitches

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Open both SSD doors before lifting the main board. The 3mx senses its SSD doors with a pair of microswitches set at an angle, and prising the main board up with the doors closed snaps the plastic tips off the switch buttons. The machine then does not recognise SSDs in either slot.[2] Psion's own disassembly procedure for the 3a also starts by opening both SSD doors fully.[3] If the switches are already broken, the repair is in the Psion Series 3mx Troubleshooting Guide.

Batteries and power

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Series 3mx power[4]
Item Specification
Main cells 2 × AA
Backup cell CR2025 lithium
Mains adaptor 9 V, 250 mA
  • The backup cell is a CR2025. The Series 3, 3a and 3c take a CR1620.[4][1] The IEC codes give the sizes: a CR2025 is 20 mm across and 2.5 mm thick, a CR1620 16 mm and 2.0 mm.[5]
  • Never remove the main cells and the backup cell together, or the internal memory is lost.[6]
  • Take the AA cells out before storing the machine. If a cell has leaked, see Battery Explosion, Capacitor or Corrosion Damage.
  • The battery lead from the contacts to the main board flexes each time the lid moves and is the usual cause of battery faults in the Series 3 family; see Psion Series 3a General Maintenance.[7]

Regular cleaning

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The 3mx has a matte silver metallic paint finish.[1] Psion's instructions for the 3c, which apply to the same style of machine, are to switch it off and wipe the keyboard and screen with a soft, clean, dry cloth, and not to use water or solvents.[6]

Serial and infrared ports

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The serial port runs at up to 115 kbit/s. Psion's Travel Modem connects to the 3c and 3mx differently from the Series 3 and 3a, so accessories for the older machines do not carry over.[1] Keep the infrared window clean.

Capacitors

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Psion published no component-level parts list for the Series 3 family. Its Series 3a service manual recommends repair at board level because the boards use high-density surface-mount parts.[3]

Preventive maintenance checklist

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  1. Back up the internal disk to an SSD or a PC.
  2. Confirm that the backup cell is a CR2025 and check its status in "Battery info".
  3. Remove the AA cells for storage and check the compartment for corrosion.
  4. With a pack in each slot, open and close each SSD door and confirm the file list updates.
  5. Check the hinges and confirm the button bar sits flush and responds.
  6. Check that the backlight works.
  7. Clean the infrared window.
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References

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  1. ↑ 1.0 1.1 1.2 1.3 "Psion Series 3", Wikipedia. The 3mx as an upgraded 3c, the silver finish, the backlight, the CR2025 backup cell, the 115 kbit/s serial port and the Travel Modem connections.
  2. ↑ R. Zealley, "Psion Series 3mx SSD door microswitch repair", Retro Coding, 25 May 2020. The 3mx door microswitches, how they break, and their repair.
  3. ↑ 3.0 3.1 Psion PLC, Series 3a Service Manual, Version 1.0, June 1996, part no. 6103-0114-01. Hosted on this wiki as File:Psion Series 3a Service Manual (June 1996).pdf. Disassembly procedure (pp. 9–12).
  4. ↑ 4.0 4.1 "Psion specifications" (Psion 3mx, Psion 5, Psion 5mx, Revo and Revo Plus), netogram.com. Series 3mx power, backup cell and communications.
  5. ↑ "Button cell", Wikipedia. IEC designation system and dimensions of CR2025 and CR1620 cells.
  6. ↑ 6.0 6.1 Psion PLC, Series 3c User Guide, Version 1.0, August 1996, part no. 6103-0107-01. Hosted on this wiki as File:Psion Series 3c User Guide (August 1996).pdf. Care (p. 22) and changing the batteries (pp. 25–27).
  7. ↑ Daniel Pfund (ed.), "PSION Series 3/3a palmtop FAQ", part 3/6, v2.6, posted to comp.sys.psion.announce and comp.answers; copy hosted by David MacKay. Section 4.1.2, the battery lead.


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