Psion Series 5 General Maintenance

Psion Series 5 (photo: Centre for Computing History)

The Psion Series 5 was launched in 1997. Psion's service manual for it, the Psion Series 5 Service Manual, covers the disassembly, spares and factory testing. The main wear items are the screen ribbon cable, which cracks after years of opening and closing, and the plastic hooks that hold the hinge spring wires. The machine runs from two AA cells and has no mains voltage inside; its CMOS parts are static-sensitive. The Psion Series 5mx has a similar case, but its main board, screen and screen ribbon are different parts.

Batteries and power

Series 5 power

Item	Specification
Main cells	2 × AA alkaline, up to about 35 hours
Backup cell	CR2032 lithium, 3 V
DC input	6 V, centre positive

Psion's precautions for the batteries:

• Do not remove both the lithium cell and the main cells without first backing up, unless an external supply is connected. Removing both erases the internal memory.
• Release the lithium cell with the stylus, inserted beneath the cell next to the voltage markings in the base moulding. A metal tool can short it.
• There is a danger of explosion if the lithium cell is replaced incorrectly. Replace it only with the same or an equivalent type.
• Some battery brands are shorter than the European average and make poor contact, which gives false low-battery warnings.
• Rechargeable cells give a very short running time, which can look as if the Series 5 is draining them too fast.

Take the AA cells out before storing the machine. If a cell has leaked, see Battery Explosion, Capacitor or Corrosion Damage.

The user (warm) reset switch is part of the lithium cell's negative contact. Psion's fault codes list a lithium reset contact that is permanently pressed down as a cause of a failed test, with the remedy of bending the contact away from the board, so check the contact whenever the backup cell is out.

Regular cleaning

Clean the screen, the infrared window and the serial connector. Keep dust and fingerprints out from between the digitiser and the LCD if the screen assembly is ever apart; Psion's manual stresses this at reassembly.

Doors, case and hinge cover

• The battery door is part of the hinge cover assembly, with the RS-232 door and the IrDA window. Each can be snapped out and replaced.
• The battery door has a silicone-based lubricant on its running surface at both ends from the factory. Apply the same to a replacement door.
• The hinge cover comes off only with the battery door closed.
• The three case screws cut into the chassis moulding and strip easily. Do not over-tighten them.
• The case mouldings were finished as sets, and colours vary between batches. Psion's instruction was to replace the whole case set if one moulding is damaged.
• When refitting the base, check that the pen eject spring has not dropped out.

Dictaphone buttons

Psion's final test checks that each of the three dictaphone buttons presses in and releases easily on its own. A button that sticks or needs help to release is recorded as a fault and should not be worked free. Fail Ticket code 26 points at the button action (plastics or the switches on the main board), and code 07 (standby current too high) includes shorts from the metallisation of the dictaphone plastics onto the board.

Screen cable and hinges

The screen ribbon cable cracks from years of opening and closing, and produces lines across the display. On the Series 5 the cable forks, with one branch soldered to the LCD and the other held against pads on the digitiser by a metal clip. The lid's snap action comes from two spring wires, whose ends are held by plastic hooks in the base moulding. On old machines the hooks become brittle and break. Open the lid squarely and without force. See Psion Series 5 Hinge Cable Repair.

Opening the case

Psion's disassembly sequence, in outline:

1. Remove the batteries, including the lithium cell, and any Memory Disk.
2. Remove the stylus and the three case screws in the base. The "Warranty Void if Removed" label is destroyed.
3. Open the Memory Disk and lithium doors, then ease the base up from its front edge.
4. The ROM daughter board can now be unclipped and removed.
5. With the battery door closed, lever the hinge cover out of its clips with a spare stylus.
6. Remove the three main board screws, unclip the speaker and backlight flexes, lift the board and release the LCD (orange) and keyboard (blue) flexes from their ZIF sockets.

On reassembly, insert the flat cables squarely and keep their existing bends, fit new labels in place of any that were removed, and have the machine open, with the Memory Disk and lithium doors open, when refitting the main board and base so that the case and door switches are not fouled. The full procedure, including separating the screen, is in Psion Series 5 Hinge Cable Repair.

Connector and socket corrosion

The ROM daughter board plugs into a socket on the main board. Psion notes that dry or faulty joints on the daughter board cause intermittent faults. Peter Vis cured a Series 5 that intermittently failed to see all its memory by cleaning green oxide from the daughter board's pins with contact cleaner. A replacement daughter board must have the same OS build and language, which the System screen shows with Ctrl+H.

Capacitors

Psion recommended repair at circuit-board level rather than component level, because of the high-density surface-mount construction. The service manual has no component list or capacitor values. See Psion Series 5mx Capacitor Replacement Guide for the 5mx.

Preventive maintenance checklist

1. Back up before touching the batteries.
2. Check the lithium cell and that its contact is not bent down towards the board.
3. Try a different brand of AA cell before trusting a low-battery warning.
4. Check that the battery door turns smoothly.
5. Press each dictaphone button and check that it releases on its own.
6. Open and close the case and the CompactFlash door and check that the machine reacts.
7. Check the display for lines, and the lid for a weak or uneven snap action.

Related pages

• Psion Series 5
• Psion Series 5 Troubleshooting Guide
• Psion Series 5 Hinge Cable Repair
• Psion Series 5 Service Manual
• Psion Series 5mx General Maintenance
• Battery Explosion, Capacitor or Corrosion Damage
• Recommended Tools