Psion Series 5 Troubleshooting Guide

A Series 5. This is the one Psion for which the factory service manual survives, complete with the Final Test fault-code table — which is effectively Psion's own list of what they expected to fail.

Fault-finding for the Psion Series 5 (1997).

The Series 5 shares its mechanics with the 5mx, so the symptom table, the blind-backup procedure and the reset levels in the Psion Series 5mx Troubleshooting Guide apply here. What this page adds is the material that is genuinely Series 5-specific — and, because Psion's own service manual survives for this machine, a good deal of factory diagnostic detail.

⚠️ Before you start

• Back up first. Removing both the main cells and the lithium cell without external power erases the internal memory.
• Use the stylus, not a metal tool, to lever out the lithium cell.
• Do not bend the LCD module or the daughter PCB — both fracture.
• Anti-static discipline throughout.

Step 1: which machine is it?

Confirm you have a Series 5 and not a 5mx before ordering any part. They look alike and their mainboards, screens and screen ribbon cables are different and not interchangeable.

A Series 5 has a CL-PS7110 at 18.432 MHz with 4 or 8 MB; a 5mx has Psion's Windermere SoC at 36 MHz with 8 or 16 MB.

Step 2: which reset happened?

The Series 5 has two, and they have opposite consequences:

Resets

Reset	Mechanism	Effect
User reset (warm)	A switch that forms part of the lithium backup battery's negative contact. Reached by opening the backup battery cover and using a pointed instrument	Vectors the CPU to a warm restart. All user data should be recovered.
Power-On Reset (cold)	A Ricoh RN5VLR20AA voltage detector fires when VDD crosses 2.0 V ± 2.5 %. An RC network stretches the pulse	Erases all data held in volatile storage. Indicates that all power was lost and re-applied.

A machine that resets constantly may have a bent lithium contact. Psion list "lithium reset contact permanently down" as a fault cause, with the fix being to bend the contact away from the PCB. The reset line is held inactive high by pull-up R1, with capacitor C113 providing noise bypass against inadvertent resets from ESD — so a machine resetting on static is a related symptom.

Step 3: measure the standby current

Psion's own figures, measured with the processor asleep at 2.75 V:

Model	Standby current
4 MB	1.50 mA
8 MB	2.10 mA

If a machine is well above that, Psion's own Final Test attributed excessive standby current to the DRAM on the PCB, dry joints and floating inputs, and shorts caused by metallisation of the plastics onto the PCB. The case mouldings are metallised for EMC, and flakes of that plating shorting onto the board is a real, factory-recognised failure mode.

Step 4: the Final Test fault codes

Psion's factory tester printed a numeric Fail Ticket for each failure. Even without the rig, this is Psion's own fault-to-assembly map — the most useful single diagnostic table for the machine.

Series 5 Final Test Fail Ticket codes

Code	Test	What to check	Assembly
01	Too much current	—	PCB
03	No response to the wake-up signal (DSR), or did not boot into the test program (no DTR)	Battery module contacting the positive contact; the unit's battery spring clip present; expansion connector DSR and DTR	PCB battery spring; PCB expansion connector
04	Failed Tx/Rx communication	CompactFlash fully inserted; CF door fully shut and the device detected; ROM board connections; expansion connector Tx/Rx; lithium reset contact permanently down	Plastics cam operator and PCB door switch; PCB ROM board connector; PCB 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 PCB; dry joints, floating inputs; shorts from metallisation of plastics onto the PCB	PCB; dictaphone plastics
08, 10	LCD connector	—	LCD
09	Backlight connector	—	Backlight
11	Keyboard connector, keys	—	Keyboard
12	Expansion connector Tx, Rx	—	PCB expansion connector
13	Expansion connector RTS, DTR, CTS, DSR, DCD	—	PCB expansion connector
14	IrDA not blocked	—	PCB IrDA devices
15	Lithium cell in socket; dry joints on the lithium contacts	—	PCB; lithium contacts
16	DC jack lead properly inserted	—	PCB DC jack socket
17	Expansion connector Vin2+ and ground	—	PCB expansion connector
18	Expansion connector shield	—	PCB expansion connector
19	Expansion connector Vpc	—	PCB expansion connector
22	Unit properly seated, speaker fitted correctly	—	Speaker
23	Unit properly seated, microphone fitted	—	PCB microphone
24	Case switch stuck open	—	PCB case switch
25	Digitiser connections	—	Digitiser
26	Action of the dictaphone buttons	—	Plastics; PCB dictaphone switches
27	Case switch stuck closed	—	PCB case switch
28	Dictaphone status LED	—	PCB status LED
29	Plastic cam operator of the CompactFlash door	—	Plastics; PCB CF door switch
31	Lithium and CompactFlash removed	—	PCB
33	ROM board devices	Test program setup	Wrong unit build

What the test tells you about the CompactFlash slot

Psion note that the CF interface is implied to be working if the unit boots into test mode — there is no separate check of every line, because booting from CompactFlash requires good conformance anyway.

Crucially: to boot successfully the CompactFlash door switch must be closed and the card properly inserted. If the door switch does not operate, the test program 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 whether the disk is detected.

Step 5: the daughter PCB

Certain intermittent faults are caused by dry or faulty joints on the ROM daughter PCB. Psion recommend swapping it early as a quick way to confirm.

Two conditions:

• Do not bend the daughter PCB during removal — it is prone to fracture.
• A replacement must be the same OS build number and language. Check with Ctrl+H in the System screen.

Step 6: display faults

The LCD needs its rails sequenced so that no residual DC is left across the panel; DC causes the liquid crystal to drift and eventually damages its polarisation permanently. That is why the display is re-initialised at every power-up, and why a half-powered machine can show odd artefacts that are not in themselves a panel fault.

Symptom	Cause	Action
Horizontal lines across the display	Cracked screen ribbon — the dominant fault on this platform	Replace the cable. The Series 5 cable is not the same as the 5mx's. See Psion Series 5 Hinge Cable Repair.
Display works only when the lid is part-open	Cracked ribbon, not yet fully open circuit	Back up immediately, then replace the cable.
Missing rows or columns in a test pattern	LCD connector or the panel	Psion's own display test checks for exactly this.
Backlight dead	Backlight connector, or the backlight itself	Fail code 09. Psion warn the backlight is delicate and prone to damage during servicing.
Touchscreen inaccurate	Calibration lost	Factory calibration is stored in non-volatile memory and is lost if the unit loses all power. Recalibrate through the OS.
Touchscreen dead in one axis	One of the four digitiser connections open	Fail code 25.

Everything else

For the blind-backup procedure, the reset levels, the case-open microswitch, the stylus catch, the battery-current check and the general symptom table, see Psion Series 5mx Troubleshooting Guide — it is the same platform.

Related pages

• Psion Series 5 · Psion Series 5 General Maintenance · Psion Series 5 Hinge Cable Repair
• Psion Series 5 Service Manual
• Psion Series 5mx Troubleshooting Guide — the shared platform diagnostics
• Battery Explosion, Capacitor or Corrosion Damage · Recommended Tools