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Psion Series 5mx Pro Troubleshooting Guide

From RetroTechCollection
A Series 5mx Pro. Before diagnosing anything else, establish whether the machine is faulty or simply asking for the CompactFlash card it boots from.

Fault-finding for the Psion Series 5mx Pro.

The 5mx Pro is a Series 5mx with no ROM. Everything in the Psion Series 5mx Troubleshooting Guide applies — the screen ribbon, the hinge hooks, the case-open microswitch, the stylus catch, the battery current check and the Final Test fault codes.

This page covers the boot-related faults that are unique to the Pro, and they account for most Pro machines that look dead.

Step 1: is it actually broken?

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A 5mx Pro with no operating system available does not fail silently. On startup it asks whether to insert a CompactFlash card containing the SystemRom, or to make a serial connection and load the system over yModem.[1]

If you see that prompt, the machine is working. It is telling you what it needs.

Pro-specific boot symptoms
Symptom Assessment Action
Asks for a CompactFlash card with the SystemRom Not a fault. The Pro has no ROM and loads its OS from card Fit the OS card. If it is lost, source or restore a Sys$rom.bin image and write it to a card, or use the yModem serial route.[1]
Offers a serial connection instead Not a fault. The documented recovery path Connect a serial cable and load the system image by yModem.[1]
Booted once, now hangs Could be the card, the CompactFlash door switch, or a genuine board fault Try a different card and confirm the door switch works before condemning the board.
Card works in a reader but not in the Psion CompactFlash door switch. The machine will not read a card with the door reported open Psion's field check: select drive D: in the System window and open and close the door to see the disk detected.[2]
Lost everything after a flat battery Expected on a Pro. A total loss of power erases the RAM — which on this machine holds the operating system as well as your data Reload from the card. This is why keeping and imaging the card matters.[1]
RAM figure does not match what you expected Sources quote both 24 MB and 32 MB for the Pro, and some of the RAM is reserved for the OS image Not a fault. A standard 5mx has 8 or 16 MB.[1][3]

Step 2: recovering a Pro with no card

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Two documented routes:[1]

  1. Write a Sys$rom.bin image to a CompactFlash card and boot from it. The file is around 10 MB; the machine originally shipped with a 16 MB card.[4]
  2. Load the system over the serial port by yModem, using the option the machine itself offers at boot.[1]

The image is version- and language-specific in the same way a standard 5mx ROM board is, so an image from a machine of a different build may not behave correctly.

Step 3: everything else

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Once the machine boots, it is a 5mx. Go to Psion Series 5mx Troubleshooting Guide for:

  • Horizontal lines on the display — the cracked screen ribbon, the dominant hardware fault on this platform
  • A whole vertical swathe grey — a failed screen controller chip
  • Will not switch on — contrast, batteries, or the sticky case-open microswitch
  • Lid does not open or close properly — broken hinge-wire hooks, see Psion Series 5mx Hinge Repair
  • Eats batteries — the Battery Information screen at Shift-Ctrl-P
  • Stylus will not click back in — the stuck catch
  • The Final Test fault code table from Psion's own service manual

Parts

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A 5mx Pro board is not interchangeable with a standard 5mx board — the Pro has no ROM daughter arrangement to match.

Screens are interchangeable: a screen from any 5mx works on any 5mx, and Pro screens are often described as slightly brighter and crisper. A Pro with a dead board is a useful source of a screen assembly for a standard 5mx, and vice versa.

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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 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 CompactFlash card and the boot-time prompt offering CompactFlash or a yModem serial load.
  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: check, and the note that the test program will not boot if the door switch does not operate. Written for the Series 5, which shares the platform.
  3. ↑ "Psion Series 5", Wikipedia. Source for the 5mx RAM options and the description of the 5mx Pro.
  4. ↑ Ash Wolf (Ninji), "\"16 Shades of Grey\" — Building a Psion/EPOC32 Emulator", 27 December 2019. Source for the Sys$rom.bin file name, size and structure, and its use in emulator development.


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