Psion Series 3a General Maintenance

Psion Series 3a

The Psion Series 3a was launched in 1993 and every surviving example is now over 25 years old. The parts that wear out are mechanical: the hinges, the button bar, the cable to the screen and the lead from the battery contacts. The Psion Series 3c and Psion Series 3mx use a similar case and share most of these points. The machine runs from two AA cells and has no mains voltage inside, but its CMOS parts are static-sensitive, so work on an earthed mat with a wrist strap.

Identify your board and build

Psion changed the Series 3a several times during production, and the changes affect which spare parts fit.

Series 3a production changes

Change	How to tell	Why it matters
Main board revision 4.0	Boards before 4.0 support only negative-bias LCD modules. Revision 4.0 and later boards are built for either polarity; positive-bias boards have a "+" in their serial number	A negative-bias LCD module connected to a positive-bias board is damaged. Positive-bias modules have a "+" on the flexible cable near the daughter-board end
TAB LCD module (from September 1995)	The screen sits closer to the hinge, with the Psion logo and "Series 3a" printed above it; hinge springs are dyed blue (black on earlier machines)	The earlier LCD modules were no longer supplied as spares; the TAB module was offered as a retrofit kit. Seiko modules are positive bias, Hitachi modules negative
CE (EMC) build (November 1995)	CE mark on the product label	CE machines have a bezel grounding cable, an earth contact for the 3-Link port, two-piece SSD shields and a metallised base moulding
Keymat type	Early UK and most non-UK machines have keys that are not attached to the rubber mat; these are marked by two black rubber stops at the bottom of the keyframe	Loose keys fall out when the keymat is lifted

Regular cleaning

Case, screen and keyboard

Psion's instructions are to switch the machine off and wipe the keyboard and screen with a soft, clean, dry cloth, and not to use water or solvents on the assembled machine. The keys can leave marks on the screen when the case is closed; clean them off regularly, because marks left for a long time can become permanent.

The Psion Series 3c and Psion Series 3mx have a rubberised finish that can turn sticky with age. See Psion Series 3c General Maintenance for the treatment.

Keyboard

Psion's fault table gives three causes of keys that do not work: a split keymat, a membrane fault, or a main board fault. Reaching the keymat means removing the keyframe (see Opening the case). On machines whose keys are not attached to the mat, lift the mat slowly so that the keys stay in place.

Batteries and power

Series 3a power

Item	Specification
Main cells	2 × AA alkaline, about 80 hours of use
Backup cell	CR1620 lithium, under SSD door B
Mains adaptor	9–10 V, 150 mA

• Never remove the main cells and the backup cell at the same time. With both out the machine loses everything in internal memory within a few seconds.
• Psion says the backup cell should last several years. When "Replace backup battery" appears, change it within a week or two, with the main cells in place.
• Lever the old backup cell out with a fingernail or a blunt non-metallic tool; a metal tool can short it. Fit the new cell with the flat "+" side upwards.
• Take the AA cells out before storing the machine, and see Battery Explosion, Capacitor or Corrosion Damage if they have leaked. Psion's user guide advises replacing rechargeable cells with alkaline ones if the machine is to be left unused.
• Some battery brands are shorter than others and make poor contact, which gives false low-battery warnings. NiCd cells have a lower voltage and give a short running time, which can look like a fault.
• If the machine keeps asking for a new backup cell that is known to be good, the cell's contact may be poor. Owners have cured this with a small piece of paper behind the cell, kept clear of the contact itself.

The battery lead

The two wires from the battery contacts to the main board flex every time the lid is opened and closed. When they break, the machine gives low-battery warnings, switches off unexpectedly, or replaces its alarms with short beeps. Psion supplied battery wires to service centres in packs of 100 and recommended replacing them whenever a machine was dismantled. The FAQ circulated on comp.sys.psion described this as the most common battery fault, and noted that re-seating the two-pin connector sometimes cures it. The rewiring procedure and parts are in the Psion Series 3a Troubleshooting Guide.

SSD slots and door switches

• RAM SSDs hold their contents on their own lithium cell. Flash SSDs need no cell, but do not recover the space used by deleted or changed files until the whole pack is reformatted.
• The SSD doors and the expansion-port door operate switches that signal to the machine when a pack or device is taken out or put in. If the file lists do not update when a door is closed, Psion's fault table points first at a door switch out of place, then the daughter board, then the main board.
• The SSD door mouldings were produced as a set with the outer keyboard moulding. Do not over-tighten their screws; the doors should open smoothly and not rattle when open.

Hinges and the button bar

The Series 3a has four hinges: two visible ones at the ends of the button bar, which have a metal pin, and two hidden plastic pegs between the battery compartment and the button bar. David MacKay found that the right-hand visible hinge breaks about 2 mm above the hinge, and attributed it to over-opening the lid, which bends the pin and twists the 8 mm neck that joins the hinge to the lid. Open the lid to its natural stop and no further. All four hinges can be repaired; see Psion Series 3a Hinge Repair.

The button bar is held against the case by two hinge springs. With the battery housing removed it bows outwards under the spring pressure and can catch as the case is closed, so press it flat when reassembling.

Opening the case

Back up the internal disk first. The procedure below is Psion's.

1. Remove the main cells and the backup cell.
2. Open both SSD doors fully and remove the screw near each door pivot. The screw in door A is under a tamper-proof label.
3. Remove the battery cover and the four screws holding the battery housing.
4. Lift the battery housing away, pull the heat-sleeved part of the battery cable from its clip and unplug the battery connector, gently, with pliers.
5. Unclip the keyframe at the centre of its front edge, hinge it up and slide it out from under the hinges.
6. Lift off the keymat.
7. Lever the main board up at its front edge using the leverage slot, easing it out of its socket on the daughter board. Pushing the expansion-port door slightly inwards helps. Lift the board out when it is at about 30°.
8. To go further, remove the hinge springs and the hinge link, release the locking bars on the ZIF connectors to free the LCD and membrane cables, and remove the two screws holding the daughter board.

On reassembly, insert the flat cables squarely into the ZIF sockets (an angled cable can short or go open circuit), push the hinge pins fully home so their heads are flush, and fit each hinge spring into its own left or right socket. Do not bend the LCD module: its circuit board can crack.

Capacitors

Psion's service manual recommends repair at board level rather than component level, because the board uses high-density surface-mount parts, and it publishes no component list. Visible corrosion from a leaked cell is a corrosion repair; see Battery Explosion, Capacitor or Corrosion Damage.

Recommended tools

Psion lists the following for dismantling the Series 3a:

• Pozidriv screwdrivers, sizes 00 and 1
• Knife or scalpel
• Straight-point tweezers
• Snipe-nose pliers

Add an anti-static wrist strap and mat, a fresh CR1620, fresh AA alkaline cells, and a 9–10 V, 150 mA adaptor for bench work. See Recommended Tools for general workshop equipment.

Preventive maintenance checklist

1. Back up the internal disk to an SSD or a PC.
2. Remove the AA cells if the machine is going into storage, and check the battery compartment for corrosion.
3. Check the backup cell's status in the System screen's "Battery info".
4. Open and close the lid and check that the button bar sits flush and all its buttons respond.
5. Check all four hinges for cracks.
6. Insert an SSD in each slot, close the door and confirm that the file list updates.
7. If the machine is opened, fit new battery wires, as Psion recommended.

Related pages

• Psion Series 3a
• Psion Series 3a Troubleshooting Guide
• Psion Series 3a Hinge Repair
• Psion Series 3 General Maintenance
• Psion Series 3c General Maintenance
• Psion Series 3mx General Maintenance
• Battery Explosion, Capacitor or Corrosion Damage
• Recommended Tools