Psion Series 3 Troubleshooting Guide

Psion Series 3

The Psion Series 3 is Psion's first clamshell organiser, released in 1991. Most of its faults are shared with the Psion Series 3a, and the Psion Series 3a Troubleshooting Guide has Psion's own fault table for that machine. The differences that matter when diagnosing a Series 3 are its three-chip architecture, its lack of a hardware real-time clock, and its lower specification.

Preliminary and power-up checks

Back up the internal disk before starting. Removing the main batteries and the backup cell together erases the internal memory. Note the time and date: a Series 3 loses them whenever the main batteries are out (see Clock and backup battery). The boards are CMOS and static-sensitive, so work on an earthed mat with a wrist strap.

Power and battery symptoms

Symptom	Probable cause	Action
Low-battery warnings with fresh cells, or unexpected switch-off	Poor contact between the cells and the battery contacts	Clean the contacts. Some battery brands are slightly shorter than others; try a different brand.
Warnings or switch-off that come and go as the lid is opened and closed	Broken wires in the lead between the battery contacts and the main board	See Battery lead
Alarms replaced by short, loud beeps	Not enough power to play the chosen alarm: flat cells, poor contacts or the battery lead	Fit fresh alkaline cells, then check the contacts and the lead
"Replace backup battery" with a new cell	Poor contact at the backup cell	Check the cell's contact; a small piece of paper behind the cell, clear of the contact, has cured this
Clock wrong after the machine has been stored with the main batteries out	Normal on a Series 3	Set the clock. See Clock and backup battery

Battery lead

The lead that joins the battery contacts to the main board twists every time the lid opens. On older Series 3 machines the wires eventually break or short, and the FAQ maintained on comp.sys.psion called this the "dreaded battery lead problem" and the first thing to check on any battery fault. To reach it:

1. Remove the main batteries and the backup cell (after backing up).
2. Remove the screws behind the batteries.
3. Unplug and re-seat the two-pin connector. This alone sometimes cures the fault.
4. If it does not, replace the two wires.

Psion sold battery wires to service centres in packs of 100 and advised fitting new wires whenever a machine was dismantled, because they flex every time it is opened and closed. The Psion Series 3a Troubleshooting Guide gives the connector and wire parts other owners have used.

Clock and backup battery

The Series 3 has no hardware real-time clock. Its ASIC1 and ASIC2 keep time with a free-running counter while the processor is powered down, and the processor has to wake about every eight hours to update it. With no main batteries the processor cannot start, and the time is lost. The backup cell, a CR1620, keeps the memory but not the clock. The Series 3a added a separate 32-bit clock inside ASIC9 that keeps time on its own, so the same symptom on a 3a or later machine is a fault.

Display faults

Symptom	Probable cause	Action
Vertical lines across the display	Deterioration of the cable that links the keyboard half to the screen	See the jail-bar section of the Psion Series 3a Troubleshooting Guide
Individual pixels, lines or patches that stay dark	LCD fault; Psion's answer was repair or replacement	Replace the lid assembly from another Series 3
A darker area in one corner	Ageing of the LCD; the FAQ reports that it does not usually get worse	None needed
Key marks on the screen	The keys touch the screen when the case is closed	Clean the screen with a soft dry cloth. Marks left for a long time can become permanent
Blank screen through polarised sunglasses	The LCD's reflected light is polarised	Not a fault

The Series 3 display is 240 × 80 pixels, black and white, with no grey plane. A replacement lid or LCD must come from another Series 3; the Series 3a panel is 480 × 160.

Keyboard and button bar

The button bar between the two halves of the case carries the application buttons. On older Series 3 machines it tends to lift, and much-used buttons can stop working. The FAQ recommended replacement, or glue on machines out of warranty. The Series 3 manual lists key presses that duplicate every button.

On the Series 3a the usual cause of a dead button bar is its thin blue ribbon cable coming out of its connector on the lower board after a knock; the reseating procedure is in the Psion Series 3a Troubleshooting Guide.

Component-level diagnosis

The three-chip architecture

The Series 3 is built around three principal chips: an NEC V30H processor and two Psion gate arrays, ASIC1 and ASIC2. The Series 3a and later machines integrate all three into a single chip, ASIC9. The processor runs at 3.84 MHz, limited by the speed of the mask ROMs that ASIC1 reads as two 8-bit bytes per 16-bit word.

Functions of ASIC1 and ASIC2

Chip	Functions
ASIC1 (about 4,300 gates, 100-pin QFP)	Bus controller (including stopping the processor clock on a HALT instruction), bus converter, 16-bit timer, LCD controller, memory and I/O decoding, interrupt controller, watchdog timer, address and I/O protection
ASIC2 (about 2,200 gates, 80-pin QFP)	System clock oscillator, switching between the standby and operating states, the eight-channel serial controller for the power supply, SSDs, expansion ports and high-speed link, keyboard scanning, buzzer, and NMI generation from power-fail and the SSD and expansion door switches

In the idle state the processor clock is stopped and the processor waits for an interrupt; only LCD refresh uses the bus. A machine that has stopped responding and is drawing idle-level current is therefore waiting for an interrupt, which does not by itself show that the processor has failed.

Current consumption

Psion's factory final test measured current through the battery terminals from a bench supply. The limits for the Series 3 are 0.250 mA in standby and 20.0 mA on and idle. The test applied 4.2 V to a Series 3 for the standby measurement and 2.5–2.6 V with a 500 mA limit for the operating tests. A standby current well above 0.25 mA drains the cells with the machine switched off.

Sound and communications

These are normal on a Series 3 and are not faults:

• It cannot record sound. The Series 3 has a piezo beeper and no microphone; recording arrived with the Series 3a.
• It has no communications software of its own. On the Series 3 the comms software is held in the link pod, and the serial link runs at 9,600 baud.

The beeper can generate DTMF tones for dialling a telephone held against it.

Hinges and case

The Series 3 has four hinges, and any of them can break. A back edge that sits crooked when the lid is opened usually means a broken hidden hinge. See Psion Series 3 Hinge Repair.

Related pages

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