Editing Psion Series 5mx Troubleshooting Guide

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[[File:Psion Series 5mx.jpg|thumb|360px|Psion Series 5mx]]

Troubleshooting guide for the '''[[Psion Series 5mx]]'''. Start with the batteries and the screen contrast, which Psion's own troubleshooting section checks first when the machine seems not to switch on.<ref name="ug-184">Psion Computers PLC, ''Psion Series 5mx User Guide'' (1999), p. 184 (troubleshooting). Hosted on this wiki: [[:File:Psion Series 5mx User Guide (1999).pdf]].</ref> Known hardware faults include a cracked screen ribbon cable, broken hinge-wire hooks and a sticking case switch.<ref name="r3uk" /><ref name="epocfaq" /> Psion's service manual was written for the [[Psion Series 5]]; the 5mx has the same case, connectors and disassembly, but a different processor and screen ribbon, so figures from it are marked as Series 5 figures below.<ref name="s5sm-17">''Psion Series 5 Service Manual'', Psion Computers PLC, November 1997, PDF pp. 17-18 (disassembly introduction). Hosted on this wiki: [[:File:Psion Series 5 Service Manual (November 1997).pdf]].</ref><ref name="r3uk">David Savery, [https://www.r3uk.com/index.php/tech-tips/34-disassembly-guides/9-psion-series-5mx-disassembly-and-screen-cable-repair "Psion Series 5MX disassembly and screen cable repair"], R3UK, 6 July 2004. Retrieved 2026-09-30.</ref>

== Preliminary checks ==

* Back up first if the machine works at all. Removing both the AA cells and the lithium backup cell without external power erases the internal memory.<ref name="s5sm-17" />
* Take anti-static precautions before opening the case. The machine contains CMOS devices.<ref name="s5sm-17" />
* Do not bend the LCD module. Its circuit board fractures easily, and the drivers along the bottom edge of the LCD are very fragile.<ref name="s5sm-17" /><ref name="s5sm-26">''Psion Series 5 Service Manual'', PDF p. 26 (reassembly instructions).</ref>
* If the LCD breaks, keep the liquid crystal away from mouth and eyes, and wash it off skin at once with soap and plenty of water.<ref name="s5sm-17" />
* Lever the lithium cell out with the stylus. A metal tool can short it.<ref name="s5sm-17" />

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Power-up symptoms'''
! Symptom !! Probable cause !! Action
|-
| Will not switch on || Flat main batteries; contrast set too low || Fit new AA cells. Adjust the contrast with Fn + M and Fn + . (full stop).<ref name="ug-184" /><ref name="ug-9">Psion Computers PLC, ''Psion Series 5mx User Guide'' (1999), p. 9 (the screen).</ref>
|-
| Will not switch on, batteries good || Case switch stuck. A raised lump under the middle of the keyboard presses a microswitch in the base when the machine is closed; the switch can stick and not spring back, so the machine behaves as if it is shut || Free the switch. See ''Mechanical faults'' below.<ref name="epocfaq">[https://www.epocfaq.co.uk/faqSeries5etc.htm "Series 5mx/5/MC218 specific"], ''The EPOC FAQ(ish)''.</ref>
|-
| Switches on but keys do nothing, or screen blank with contrast still adjustable || Software lock-up || Soft reset (see ''Resets'').<ref name="ug-185">Psion Computers PLC, ''Psion Series 5mx User Guide'' (1999), p. 185 (resetting).</ref>
|-
| Still dead after the above || Deeper fault || Remove all power for several minutes, which clears everything in RAM, then refit the batteries.<ref name="epocfaq" /><ref name="s5sm-7" />
|}

=== Backing up a machine with no usable screen ===

With a serial cable connected and PsiWin running on the PC, the link can be started blind:<ref name="epocfaq" />

# Switch on and type the power-on password if one is set.
# Tap the System icon to make sure the System screen is showing.
# Press Ctrl-L to open the Link dialog.
# Press C to select Cable.
# Press the down arrow to move to the baud rate.
# Press 5 to select 57600. Do not press 1, which could select 19200 or 115200.
# Press Enter to start the link and close the dialog.

Then right-click ''My Psion'' on the PC, check that the connection settings match, and back up.

On a machine with a cracking screen ribbon, opening the lid only about a centimetre can bring the display back for long enough to do this with the screen visible.<ref name="r3uk" />

== Resets ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Reset levels'''
! Reset !! How !! Effect
|-
| Soft reset || Press an unfolded paperclip gently into the reset hole above the backup battery || Restarts the machine. Changes to open Word or Sheet files are lost; other files on the internal disk are almost always kept.<ref name="ug-185" />
|-
| Hard reset || Press the reset hole as for a soft reset, then hold both Shift keys and press Esc to switch on || Resets the machine completely. Everything on the internal disk is lost.<ref name="ug-185" />
|-
| Total loss of power || Remove the main and backup cells || Power-on reset. Everything in volatile storage is erased, including any user recalibration of the touchscreen.<ref name="s5sm-7">''Psion Series 5 Service Manual'', PDF p. 7 (circuit description: resets).</ref><ref name="s5sm-44">''Psion Series 5 Service Manual'', PDF p. 44 (final test: digitiser calibration).</ref>
|}

The reset switch is part of the lithium backup battery's negative contact, which is why it is reached through the backup battery cover. Operating it sends the CPU to a warm restart. A power-on reset comes from a voltage detector (IC4 on the Series 5, threshold 2.0 V ± 2.5 %) when the supply rises through its set point.<ref name="s5sm-7" />

== Display faults ==

=== Screen ribbon cable ===

This is the best-known Series 5 and 5mx fault. Horizontal lines appear across the display, often suddenly and often on opening the machine. The display may still work with the lid opened only part way.<ref name="r3uk" />

The flexible ribbon that joins the main board to the screen cracks around a hole in the plastic that held the cable in place during manufacture. Years of opening and closing the lid fracture the plastic around that hole, and once the crack cuts a conductor the display fails. The crack can be too small to see without a magnifying glass. It is under the black adhesive plastic that covers the solder points.<ref name="r3uk" />

The repair is a new cable. A bridge soldered across the broken track does work, but one documented attempt lasted about four days of daily use. The solder points are tiny and easily bridged, so check each joint with a continuity tester and clear splashes by running a blade between the pads.<ref name="r3uk" /> The 5mx uses a different screen ribbon from the Series 5, so check the model before ordering.<ref name="r3uk" /> Replacement 5mx cables are sold by Psion specialists, and redesigned cables that avoid the original weak point have been made.<ref name="psionex-cable">Psionex, [https://psionex.co.uk/en/product/pda/series5/models/s5mx-24mb-pro-de.html "Psion Series 5mx Pro, 24MB"], accessories list: "Psion Series 5MX and Ericsson MC218 screen flexi cable" (SKU S5MX_SCRCBL). Retrieved 2026-09-30.</ref><ref name="epocfaq" />

Disassembly to reach the cable is in [[Psion Series 5mx Hinge Repair]] and in the R3UK guide.<ref name="r3uk" />

=== Other display faults ===

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Display symptoms'''
! Symptom !! Probable cause !! Action
|-
| Horizontal lines across the display || Cracked screen ribbon cable || Replace the cable (above).<ref name="r3uk" />
|-
| Display works only with the lid part-open || Cracked screen ribbon, not yet fully open-circuit || Back up at once, then replace the cable.<ref name="r3uk" />
|-
| A whole vertical band of the screen goes grey || Failed screen controller chip || Not a cable fault. Needs a replacement screen assembly.<ref name="epocfaq" />
|-
| Screen blank || Contrast out of range || Adjust with Fn + M and Fn + . (full stop), then try a soft reset.<ref name="ug-9" /><ref name="ug-185" />
|-
| Blank after being somewhere very hot or cold || Contrast drifts with temperature || Readjust at room temperature before looking for a fault.<ref name="epocfaq" />
|-
| No backlight || Backlight damaged or its flexi disconnected || Psion warn that the backlight is delicate and easily damaged in servicing. Check it and its flexi whenever the screen is apart.<ref name="s5sm-23">''Psion Series 5 Service Manual'', PDF p. 23 (LCD assembly).</ref><ref name="s5sm-20">''Psion Series 5 Service Manual'', PDF p. 20 (main PCB removal).</ref>
|}

== Power and battery faults ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Battery symptoms'''
! Symptom !! Probable cause !! Action
|-
| Short battery life || Unsuitable cells, or excess current draw || Open Battery Information with Shift-Ctrl-P in the System screen. "Battery current now" should be below 50 mA with no external power and the backlight off. If it is higher, try a soft reset.<ref name="epocfaq" />
|-
| Low-battery warnings with fresh cells || Some battery brands are shorter than the European average and make poor contact || Try another brand before suspecting the machine.<ref name="s5sm-27">''Psion Series 5 Service Manual'', PDF p. 27 (reassembly instructions and notes).</ref>
|-
| Rechargeable AA cells run down quickly || Expected || Psion note that rechargeables give very short running time and can make the machine look as if it is draining them.<ref name="s5sm-27" />
|}

Psion's standby figures are for the Series 5, measured with the processor asleep at 2.75 V. No 5mx figures are published, but they give the order of magnitude for the platform:<ref name="s5sm-43">''Psion Series 5 Service Manual'', PDF p. 43 (explanation of final tests).</ref>

{| class="wikitable styled-table" style="width:50%; text-align:center;"
|+'''Series 5 standby current'''<ref name="s5sm-43" />
! Memory !! Standby current
|-
| 4 MB || 1.50 mA
|-
| 8 MB || 2.10 mA
|}

The 5mx runs on two AA alkaline cells, with a CR2032 lithium cell holding RAM while the AAs are changed. The optional mains adapter is 6 V DC ± 10 %, 1 A.<ref name="ug-191">Psion Computers PLC, ''Psion Series 5mx User Guide'' (1999), p. 191 (specification).</ref>

== Input and connection faults ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Input and I/O symptoms'''
! Symptom !! Probable cause !! Action
|-
| Keyboard dead, or a block of keys dead || Keyboard flexi or its ZIF connector; corrosion in the flexi || Reseat the flexi squarely.<ref name="s5sm-26" /> Corrosion in the keyboard flexi can make a keyboard unusable on any machine.<ref name="pitc">[https://pointinthecloud.com/2025-10-13-154800.html "Repairing a Psion 5mx handheld computer to add to my collection"], Point in the Cloud, 13 October 2025. Retrieved 2026-09-30.</ref>
|-
| Touchscreen inaccurate || User calibration lost after a total loss of power || Recalibrate from the Screen icon in the Control panel. The factory calibration is kept in non-volatile memory; user adjustments are lost when all power goes.<ref name="ug-9" /><ref name="s5sm-44" />
|-
| Touchscreen dead in one axis || Digitiser connection or the digitiser itself || The digitiser has four connections that sense resistance across X and Y; one open circuit loses an axis.<ref name="s5sm-7" />
|-
| CompactFlash card not detected || CompactFlash door switch, card seating, or the ETNA controller || Check the door switch first: select drive D: in the System screen, then open and close the door and watch the card disappear and reappear.<ref name="s5sm-43" /> ETNA is an undocumented Psion chip and cannot be replaced from stock.<ref name="wuffs">Ash Wolf (Ninji), [https://wuffs.org/blog/building-a-psion-emulator "'16 Shades of Grey' - Building a Psion/EPOC32 Emulator"], 27 December 2019. Retrieved 2026-09-30.</ref>
|-
| Speaker or microphone dead || Speaker flexi connector || Lift the tags on the sides of the connector and reseat the flexi.<ref name="s5sm-20" /><ref name="r3uk" />
|-
| Serial link will not connect || Baud rate mismatch, cable, or the expansion connector || Set the link to 57600 explicitly instead of relying on a saved setting.<ref name="epocfaq" />
|}

== Mechanical faults ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Mechanical symptoms'''
! Symptom !! Probable cause !! Action
|-
| Lid does not open or close properly; screen flops || Broken hinge-wire hook in the inner chassis || See [[Psion Series 5mx Hinge Repair]].
|-
| Machine does not switch off when closed, or on when opened || Case switch sticking || The raised lump under the keyboard should press the microswitch as the lid closes and release it as the lid opens.<ref name="epocfaq" />
|-
| Stylus will not click back into its slot || Catch stuck closed inside the case || Slide something thin and stiff, such as a metal rule or a fingernail, into the gap in the case below the serial socket until the catch clicks open. As a last resort, open the backup battery cover and slacken the screw under the warranty seal by half a turn to release the catch, then retighten it.<ref name="epocfaq" />
|}

== Board faults ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Board symptoms'''
! Symptom !! Probable cause !! Action
|-
| Intermittent crashes || Dry or faulty joints on the daughter (ROM) PCB || Psion name this as a cause of intermittent faults. The daughter PCB unclips and eases out of its socket for a swap test. A replacement must have the same OS build and language; check with Ctrl+H in the System screen.<ref name="s5sm-19">''Psion Series 5 Service Manual'', PDF p. 19 (daughter PCB and hinge cover).</ref>
|-
| Constant resets, or unexplained behaviour after reassembly || Lithium reset contact held down || Psion's fix is to bend the contact away from the PCB (Fail Ticket code 04).<ref name="s5sm-45">''Psion Series 5 Service Manual'', PDF p. 45 (Fail Ticket codes).</ref>
|-
| Corroded board, green vias || Past battery leak || Clean and inspect. A board with corroded vias may be beyond saving.<ref name="pitc" /> See [[Battery Explosion, Capacitor or Corrosion Damage]].
|}

=== Factory test fault codes ===

Psion's Final Test unit printed a numbered Fail Ticket for each failure. The table is Psion's mapping from code to check and replacement part, written for the Series 5.<ref name="s5sm-45" /> It is still a guide to which assembly to suspect. The "Honda connector" in Psion's table is the expansion (serial) connector.<ref name="s5sm-43" />

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Series 5 Final Test Fail Ticket codes'''<ref name="s5sm-45" />
! Code !! Test !! Check !! Change
|-
| 01 || Too much current || || PCB
|-
| 03 || No response to the wake-up signal || Battery module touching the positive contact; battery spring clip present; expansion connector DSR and DTR || PCB battery spring; PCB expansion connector
|-
| 04 || Failed Tx/Rx communication || CompactFlash fully inserted; CompactFlash door fully shut and card detected; ROM board connections; expansion connector Tx/Rx; lithium reset contact permanently down || Door switch and its plastic cam; ROM board connector; expansion connector; bend the lithium contact away from the PCB
|-
| 06 || Language, RAM size || Test program setup || Wrong unit build
|-
| 07 || Standby current out of limits || DRAM on the PCB; dry joints and floating inputs; shorts from metallisation of the plastics onto the PCB || PCB; dictaphone plastics
|-
| 08, 10 || LCD connector || || LCD
|-
| 09 || Backlight connector || || Backlight
|-
| 11 || Keyboard connector, keys || || Keyboard
|-
| 12, 13 || Expansion connector Tx/Rx, and RTS/DTR/CTS/DSR/DCD || || PCB expansion connector
|-
| 14 || IrDA not blocked || || PCB IrDA devices
|-
| 15 || Lithium cell in socket; dry joints on lithium contacts || || PCB; lithium contacts
|-
| 16 || DC jack lead properly inserted || || PCB DC jack socket
|-
| 17, 18, 19 || Expansion connector Vin2+/ground, shield, Vpc || || PCB expansion connector
|-
| 22 || Speaker fitted correctly || || Speaker
|-
| 23 || Microphone fitted || || PCB microphone
|-
| 24, 27 || Case switch stuck open / stuck closed || || PCB case switch
|-
| 25 || Digitiser connections || || Digitiser
|-
| 26 || Dictaphone buttons || || Plastics; PCB dictaphone switches
|-
| 28 || Dictaphone status LED || || PCB status LED
|-
| 29 || Plastic cam operator of the CompactFlash door || || Plastics; PCB CompactFlash door switch
|-
| 31 || Lithium cell and CompactFlash removed || || PCB
|-
| 33 || ROM board devices || Test program setup || Wrong unit build
|}

Code 07 lists shorts from the metallised plastics onto the PCB as a cause of excess standby current, so a machine that drains its batteries while switched off may have exactly that.<ref name="s5sm-45" />

== Repairability and parts ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Repair options by part'''
! Part !! Repairable? !! Notes
|-
| Screen ribbon cable || Yes || The usual repair. The 5mx and Series 5 cables differ.<ref name="r3uk" />
|-
| Inner chassis and hinge hooks || Yes || Wire-tie workaround, or a 3D-printed chassis. See [[Psion Series 5mx Hinge Repair]].
|-
| Keyboard || With a donor || Psion supplied keyboards as complete assemblies, language-specific.<ref name="s5sm-23" />
|-
| LCD and digitiser || With a donor || Psion recommend replacing the LCD and digitiser as one assembly: the conductive strip and clamp are placed with factory equipment and are hard to fit accurately by hand.<ref name="s5sm-23" />
|-
| Backlight || Fragile || Easily damaged in servicing; check it whenever the screen is apart.<ref name="s5sm-23" />
|-
| Daughter (ROM) PCB || With a matching donor || Must be the same OS build and language. Check with Ctrl+H in the System screen.<ref name="s5sm-19" />
|-
| Main PCB || Board swap || Psion recommend board-level, not component-level, repair. A replacement must have the same RAM size.<ref name="s5sm-17" /><ref name="s5sm-20" />
|-
| ETNA CompactFlash controller || No || A bespoke, undocumented Psion part.<ref name="wuffs" />
|}

A [[Psion Series 5mx Pro]] screen assembly has been fitted to a standard 5mx in a documented repair.<ref name="pitc" />

== Related pages ==

* [[Psion Series 5mx]]
* [[Psion Series 5mx General Maintenance]]
* [[Psion Series 5mx Hinge Repair]]
* [[Psion Series 5mx Capacitor Replacement Guide]]
* [[Psion Series 5mx Pro Troubleshooting Guide]]
* [[Psion Series 5 Service Manual]]
* [[Battery Explosion, Capacitor or Corrosion Damage]]
* [[Recommended Tools]]

== References ==

<references />

{{Navbox-Psion|state=collapsed}}

[[Category:Psion]]
[[Category:Troubleshooting Guides]]