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Psion Series 5mx Pro General Maintenance

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A Series 5mx Pro. Mechanically it is a 5mx — but it will not boot without its CompactFlash card, which makes that card part of the machine rather than an accessory.

Preventive maintenance for the Psion Series 5mx Pro.

The 5mx Pro is mechanically and electrically a Series 5mx, so the whole of Psion Series 5mx General Maintenance applies: the batteries, the doors, the stylus catch, the case-open microswitch, the flat flexible cables, the hinge discipline and the screen ribbon.

This page covers the one thing that is genuinely different, and it is a maintenance issue rather than a hardware one.

The CompactFlash card is part of the machine

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The Pro has no ROM. Its operating system is a file — Sys$rom.bin, around 10 MB — loaded into a reserved area of RAM from a CompactFlash card at boot. The machine shipped with a 16 MB card carrying it.[1][2]

That changes what maintenance means on this machine:

  • Keep the card with the machine. A 5mx Pro separated from its OS card is not a working computer.
  • Take an image of the card now, before you need it. Copy Sys$rom.bin off and keep it somewhere safe. Cards from 1999 are not getting younger, and this one is a single point of failure.
  • Label the card so it does not get formatted by mistake — it looks like an ordinary CompactFlash card in a reader.
  • Keep the CompactFlash door and its switch working. On this platform the machine will not read the card with the door reported open,[3] and on a Pro that means it will not boot at all. Psion's own field check is to select drive D: in the System window and open and close the door to see the disk detected.[3]
  • Know the serial recovery route. If the card is lost or unreadable, the machine offers to load the system over a serial connection using yModem.[2] Have a cable and a terminal program that can do yModem before you need them, not after.

Batteries

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As a 5mx: two AA cells and a lithium backup cell. Removing both without external power erases the internal memory[3] — and on a Pro that includes the operating system image held in RAM, so the machine will go back to asking for its card.

That is worth restating plainly: on a 5mx Pro, a total loss of power costs you the OS as well as your data. It is recoverable from the card, but only if you still have the card.

Everything else

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See Psion Series 5mx General Maintenance for the batteries, doors, catches, switches, cables, hinge discipline and screen ribbon care — all of which are identical.

For capacitors, the answer is the same as for the standard machine: not a recap candidate. See Psion Series 5mx Capacitor Replacement Guide.

Preventive maintenance checklist

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  1. Image the OS CompactFlash card and store the image safely.
  2. Confirm the CompactFlash door switch operates — watch drive D: appear and disappear.
  3. Back up user data as on any 5mx.
  4. Replace the lithium backup cell if you do not know its age.
  5. Then work through the Psion Series 5mx General Maintenance checklist.
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References

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  1. ↑ Ash Wolf (Ninji), "\"16 Shades of Grey\" — Building a Psion/EPOC32 Emulator", 27 December 2019. Source for the boot-from-CompactFlash arrangement and the Sys$rom.bin file name and size.
  2. ↑ 2.0 2.1 Community discussion of the differences between the Psion 5mx and 5mx Pro, comp.sys.psion.misc. Source for the absence of ROM, the reserved RAM region, the supplied 16 MB card and the boot-time prompt.
  3. ↑ 3.0 3.1 3.2 Psion Series 5 Service Manual, Psion Computers PLC, November 1997. Hosted on this wiki as File:Psion Series 5 Service Manual (November 1997).pdf. Source for the CompactFlash door switch requirement, the drive D: field check, the battery removal warning and the general handling cautions. Written for the Series 5, which shares the platform.


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