Psion Series 5mx Troubleshooting Guide
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.[1] Known hardware faults include a cracked screen ribbon cable, broken hinge-wire hooks and a sticking case switch.[2][3] 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.[4][2]
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.[4]
- Take anti-static precautions before opening the case. The machine contains CMOS devices.[4]
- Do not bend the LCD module. Its circuit board fractures easily, and the drivers along the bottom edge of the LCD are very fragile.[4][5]
- 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.[4]
- Lever the lithium cell out with the stylus. A metal tool can short it.[4]
| 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).[1][6] |
| 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.[3] |
| Switches on but keys do nothing, or screen blank with contrast still adjustable | Software lock-up | Soft reset (see Resets).[7] |
| Still dead after the above | Deeper fault | Remove all power for several minutes, which clears everything in RAM, then refit the batteries.[3][8] |
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:[3]
- 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.[2]
Resets
| 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.[7] |
| 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.[7] |
| 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.[8][9] |
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.[8]
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.[2]
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.[2]
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.[2] The 5mx uses a different screen ribbon from the Series 5, so check the model before ordering.[2] Replacement 5mx cables are sold by Psion specialists, and redesigned cables that avoid the original weak point have been made.[10][3]
Disassembly to reach the cable is in Psion Series 5mx Hinge Repair and in the R3UK guide.[2]
Other display faults
| Symptom | Probable cause | Action |
|---|---|---|
| Horizontal lines across the display | Cracked screen ribbon cable | Replace the cable (above).[2] |
| Display works only with the lid part-open | Cracked screen ribbon, not yet fully open-circuit | Back up at once, then replace the cable.[2] |
| A whole vertical band of the screen goes grey | Failed screen controller chip | Not a cable fault. Needs a replacement screen assembly.[3] |
| Screen blank | Contrast out of range | Adjust with Fn + M and Fn + . (full stop), then try a soft reset.[6][7] |
| Blank after being somewhere very hot or cold | Contrast drifts with temperature | Readjust at room temperature before looking for a fault.[3] |
| 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.[11][12] |
Power and battery faults
| 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.[3] |
| 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.[13] |
| 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.[13] |
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:[14]
| 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.[15]
Input and connection faults
| 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.[5] Corrosion in the keyboard flexi can make a keyboard unusable on any machine.[16] |
| 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.[6][9] |
| 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.[8] |
| 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.[14] ETNA is an undocumented Psion chip and cannot be replaced from stock.[17] |
| Speaker or microphone dead | Speaker flexi connector | Lift the tags on the sides of the connector and reseat the flexi.[12][2] |
| 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.[3] |
Mechanical faults
| 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.[3] |
| 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.[3] |
Board faults
| 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.[18] |
| 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).[19] |
| Corroded board, green vias | Past battery leak | Clean and inspect. A board with corroded vias may be beyond saving.[16] 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.[19] It is still a guide to which assembly to suspect. The "Honda connector" in Psion's table is the expansion (serial) connector.[14]
| 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.[19]
Repairability and parts
| Part | Repairable? | Notes |
|---|---|---|
| Screen ribbon cable | Yes | The usual repair. The 5mx and Series 5 cables differ.[2] |
| 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.[11] |
| 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.[11] |
| Backlight | Fragile | Easily damaged in servicing; check it whenever the screen is apart.[11] |
| Daughter (ROM) PCB | With a matching donor | Must be the same OS build and language. Check with Ctrl+H in the System screen.[18] |
| Main PCB | Board swap | Psion recommend board-level, not component-level, repair. A replacement must have the same RAM size.[4][12] |
| ETNA CompactFlash controller | No | A bespoke, undocumented Psion part.[17] |
A Psion Series 5mx Pro screen assembly has been fitted to a standard 5mx in a documented repair.[16]
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
- ↑ 1.0 1.1 Psion Computers PLC, Psion Series 5mx User Guide (1999), p. 184 (troubleshooting). Hosted on this wiki: File:Psion Series 5mx User Guide (1999).pdf.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 David Savery, "Psion Series 5MX disassembly and screen cable repair", R3UK, 6 July 2004. Retrieved 2026-09-30.
- ↑ 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 "Series 5mx/5/MC218 specific", The EPOC FAQ(ish).
- ↑ 4.0 4.1 4.2 4.3 4.4 4.5 4.6 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.
- ↑ 5.0 5.1 Psion Series 5 Service Manual, PDF p. 26 (reassembly instructions).
- ↑ 6.0 6.1 6.2 Psion Computers PLC, Psion Series 5mx User Guide (1999), p. 9 (the screen).
- ↑ 7.0 7.1 7.2 7.3 Psion Computers PLC, Psion Series 5mx User Guide (1999), p. 185 (resetting).
- ↑ 8.0 8.1 8.2 8.3 Psion Series 5 Service Manual, PDF p. 7 (circuit description: resets).
- ↑ 9.0 9.1 Psion Series 5 Service Manual, PDF p. 44 (final test: digitiser calibration).
- ↑ Psionex, "Psion Series 5mx Pro, 24MB", accessories list: "Psion Series 5MX and Ericsson MC218 screen flexi cable" (SKU S5MX_SCRCBL). Retrieved 2026-09-30.
- ↑ 11.0 11.1 11.2 11.3 Psion Series 5 Service Manual, PDF p. 23 (LCD assembly).
- ↑ 12.0 12.1 12.2 Psion Series 5 Service Manual, PDF p. 20 (main PCB removal).
- ↑ 13.0 13.1 Psion Series 5 Service Manual, PDF p. 27 (reassembly instructions and notes).
- ↑ 14.0 14.1 14.2 14.3 Psion Series 5 Service Manual, PDF p. 43 (explanation of final tests).
- ↑ Psion Computers PLC, Psion Series 5mx User Guide (1999), p. 191 (specification).
- ↑ 16.0 16.1 16.2 "Repairing a Psion 5mx handheld computer to add to my collection", Point in the Cloud, 13 October 2025. Retrieved 2026-09-30.
- ↑ 17.0 17.1 Ash Wolf (Ninji), "'16 Shades of Grey' - Building a Psion/EPOC32 Emulator", 27 December 2019. Retrieved 2026-09-30.
- ↑ 18.0 18.1 Psion Series 5 Service Manual, PDF p. 19 (daughter PCB and hinge cover).
- ↑ 19.0 19.1 19.2 19.3 Psion Series 5 Service Manual, PDF p. 45 (Fail Ticket codes).