Psion Organiser II Troubleshooting Guide

Two-line and four-line Organiser IIs. The four-line LZ and LZ64 use a different control IC and different LCD drivers from the two-line CM, XP and LA.

Fault-finding for the Psion Organiser II. Psion's Technical Manual documents the supply rails, the operating states, the power-on sequence and the expected currents, so most faults can be traced by measurement.

Preliminary checks

• Back up to a Datapak first if the machine still works. The internal memory is lost if the battery is out for more than 90 seconds.
• Remove the battery before opening the machine.
• Switch off before inserting or removing a Rampak, or its contents will be lost.
• The system board is CMOS throughout. Use an anti-static strap.
• The SVPP rail reaches 21 V during Datapak writes, from a capacitor charged to about 35 V.

Identify the machine

If it powers up, choose CALC from the main menu and evaluate:

• PEEKB(-24) for the model: 0 = CM, 1 = XP, 2 = XP (LA), 14 = LZ, 13 = LZ64. Values 17, 18, 20, 29, 30, 65, 66, 129 and 130 are POS and industrial variants.
• PEEKB(-23) for the ROM version in BCD, so $46 is version 4.6.
• PEEKB(-25) for the language options.

The LZ and LZ64 use a Texas Instruments CF70043 control IC and HD66780/HD66100 LCD drivers; the two-line machines use an NEC µPD65006 and HD44780/HD44100. Check which parts apply before ordering spares.

First checks

1. Battery. Fit a known-good alkaline PP3 and check it under load as well as off-load; the machine draws peaks of 200 mA.
2. Contrast. Sweep the thumbwheel slowly through its full travel.
3. Packs. Remove every pack and try again.
4. ON/CLEAR key. It is the only key outside the scanned matrix and is what switches the machine on, so a dirty or dead ON/CLEAR contact leaves the machine apparently dead.

Power-up sequence

Knowing the sequence shows where a failed start has stopped.

1. Pressing ON/CLEAR (AC in the Technical Manual), a rising edge on the external AC input, or a timeout of the stage 2 counter sets the ON/OFF latch in the control IC.
2. ON_B goes low immediately, switching on the supply rail regulators.
3. After a delay for the rails to settle, the control IC sequences STBY_B and RES_B. The processor sits in reset for 30 to 60 ms while the oscillator and E clock start, then runs.
4. The processor initialises the LCD. The display drivers lose power when the machine is off, so the LCD is initialised at every start-up.
5. Shutdown is started by the processor itself, by accessing the SWITCH OFF address range $01C0–$01FF.

No rails at all points to the power supply board or the ON/OFF latch. Rails present but no display points to the processor, the ROM or the LCD. A display that does not respond to keys points to the keyboard or the control IC.

Power supply diagnostics

Supply current

The current drawn from the battery is the most informative single measurement.

Expected supply current

State	Expected	If wrong
Off	About 40 µA (30 µA system board plus about 10 µA power supply quiescent)	Milliamps here means something is leaking, which also flattens batteries in storage. Check the power board electrolytics.
On, processor running	About 25 mA	Much higher with no pack activity suggests a rail that is not regulating.
On, processor asleep	About 4 mA	Never falling to this suggests the processor is not entering sleep mode.
Slots on, no devices fitted	About 25 mA internally
Slots on, peak	Up to 170 mA from the slot regulator; system peaks of 200 mA

A bench supply set to 9 V with the current limit at about 250 mA can replace the battery for these measurements; a shorted rail then shows as the current limit rather than as damage.

Rail voltages

Supply rails

Rail	Off	On	Symptom when missing or wrong
VCC1	3–5 V	5 V ±5 %	Nothing works. A reading below 5 V with the machine on and a good battery points to the main regulator.
VCC2	Off	5 V ±5 %	Display dead although the machine otherwise runs (beeps, responds to keys)
V_LCD	Off	Adjustable from +1.2 V to −3 V by the thumbwheel	No contrast control; blank or washed-out display
SVCC	Off	5 V ±5 % when the slots are switched on	Packs not recognised
SVPP	Off	4.5 V normally; 21 V ±2 % pulsed while programming	Packs read but SAVE fails

• The main regulator works down to a supply of about 5.3 V. Below that, VCC1 follows the supply about 0.3 V below it, so a machine that misbehaves on a nearly flat battery is behaving as designed.
• LOWBAT is signalled when VCC1 falls about 2 % below nominal. A persistent low-battery warning with a good cell points at the regulator or the divider chain feeding the detector.

Power symptoms

Symptom	Probable cause	Action
Completely dead	Flat or high-resistance battery; corroded battery contacts; ON/CLEAR key; ON/OFF latch; failed regulator	Fit a known-good alkaline PP3. Check VCC1 is present with the machine off, then check that ON/CLEAR reaches the control IC.
Battery goes flat in storage	Leaking electrolytic on the power board	Measure the off-state current; it should be about 40 µA.
Persistent LOW BATTERY with a good cell	Regulator or LOWBAT divider chain	LOWBAT trips at about 2 % below nominal VCC1.
Corrosion on the boards	Past battery or capacitor leakage	Neutralise, clean and inspect every track in the area. See Battery Explosion, Capacitor or Corrosion Damage.

Display faults

Display symptoms

Symptom	Probable cause	Action
Black or blank screen at switch-on	Contrast at one end of its travel	Turn the thumbwheel through its full range.
Display blank but the machine beeps and responds	VCC2 or V_LCD missing	Measure both. VCC2 is switched from VCC1 through a transistor; V_LCD comes from a charge pump.
No contrast change across the whole wheel travel	V_LCD charge pump or thumbwheel	Check that the wheel's resistance changes. If it does, check the pump and its capacitors; see the Psion Organiser II Capacitor Replacement Guide.
Missing dots, a dead column or a faded band	Conductive rubber LCD connector strip	Release the LCD clamp, clean both faces and the strip with isopropyl alcohol and reassemble squarely with even pressure. Replace the strip (Psion 3700 0002) if cleaning does not cure it.

Keyboard faults

The 35 matrix keys are scanned by outputs K1–K7 from the control IC and inputs KBD1–KBD5 on processor port 5 bits 2–6. K1–K7 are bits of the control IC's stage 2 clock counter.

Keyboard symptoms

Symptom	Probable cause	Action
One key dead	Keymat or PCB pad	Clean both. See Psion Organiser II General Maintenance.
A whole row of keys dead	One of the K1–K7 outputs	Check for a broken track between the pads and the control IC first.
A whole column of keys dead	One of the KBD1–KBD5 inputs	Trace the line back to the processor.
ON/CLEAR dead, everything else fine	ON/CLEAR contact	ON/CLEAR is wired directly to the control IC and to port 5 bit 7, outside the scanned matrix.
Numeric keypad or unusual key legends	POS variant	Confirm with PEEKB(-24).

Clock faults

Clock symptoms

Symptom	Probable cause	Action
Clock or memory lost on every battery change	Battery out for too long, or the standby hold-up on the power board has failed	Psion allows 90 seconds with the machine off. The design hold-up is 2–3 minutes above 3 V. If a quick change still loses the time, check the power board electrolytics.
Clock drifts badly while the machine is off	32768 Hz oscillator, or the stage 2 counter wake-up	The machine wakes every 34 min 8 s to update its clock; check the crystal circuit.
Machine switches itself on in a drawer	Normal	It wakes every 34 min 8 s to keep time and then switches off.

Pack and slot faults

Pack and slot symptoms

Symptom	Probable cause	Action
Packs read but SAVE fails	21 V programming pump	Reads do not use the pump; writes do. Check the pump storage capacitor and the SVPP rail.
Packs not recognised	SVCC not switched on; slot contacts; PACON_B	Clean the contacts, then check that SVCC appears when a pack operation is attempted.
One slot works, the other does not	Slot contacts or that slot's select path	Swap a known-good pack between the slots to confirm before opening anything.
Rampak has lost its contents	Flat Rampak battery, or the Rampak was inserted or removed with the Organiser on	The 32 KB Rampak's battery life is about five years.
DATAPAK FULL on a pak that seems nearly empty	Erased records still occupy space	Normal EPROM behaviour. Copy the live records to a fresh pak, or UV-format the old one.
"PACK?" or "INSERT PACK?", then the machine switches off	POS model	Normal. POS machines look for a procedure called BOOT on the fitted packs and switch off if there is none.

Psion's pack error messages, and how to copy, format and repair Datapaks, Rampaks and Flashpaks, are covered in Psion Organiser II Datapak Repair.

Audio faults

Audio symptoms

Symptom	Probable cause	Action
Persistent whistle, buzz or squeal, especially on an LZ or LZ64	Ageing electrolytics on the power supply board	Recap the power board. The Byte-My-Vdu author reports that a full recap cured the whistle, and a commenter identifies the 10 µF capacitor whose positive side connects to the buzzer as the cause. Values are in the Psion Organiser II Capacitor Replacement Guide.

The buzzer sounds only on transitions of the ALARM signal, so tones are produced by software toggling it.

Memory configuration

If a machine boots but reports the wrong amount of memory, or crashes in a way that suggests an address-decoding fault, check the memory decode links. There are eight, arranged as four pairs, and only one of each pair should be fitted.

Production link options

Version	PROM	RAM	Links fitted
CM	32 KB at $8000–$FFFF	8 KB at $2000–$3FFF	L1, L4, L5, L7
XP	32 KB at $8000–$FFFF	8 KB + 8 KB at $2000–$5FFF	L1, L4, L5, L7
LA	32 KB at $8000–$FFFF	32 KB at $0400–$7FFF	L1, L4, L6, L7

The links do the following:

• L1 routes CS1_B to a 32 KB PROM; L2 routes CS2_B to an 8 KB PROM.
• L4 makes A14 available to a 32 KB PROM; L3 pulls PROM pin 27 high when A14 is not needed.
• L6 routes CS6_B to a 32 KB RAM; L5 routes CS5_B to an 8 KB RAM.
• L7 (normally fitted) gates the chip selects with the processor E clock; L8 makes them depend on the address lines alone.

RAM must have an access time of 250 ns or better. Psion used 62256LFP (later KM62256BLG) for 32 KB and 6264LFP for 8 KB.

Repairability

What can be repaired

Part	Repairable	Notes
Power supply board	Yes	The electrolytics are leaded and Psion's parts list gives their values.
LCD connector strip	Yes	Clean it, or replace it (Psion 3700 0002).
LCD panel	With a donor	Psion part 3900 0003 for the two-line panel. The LZ uses different drivers.
Keymat	Yes	Washable; Psion part 8700 0001.
RAM and PROM	With surface-mount rework	62256/6264 static RAM and 27C256/27C64 EPROM are standard parts, and Organiser II ROM contents have been archived.
HD6303XFP processor	Difficult	80-pin flat pack.
Control IC (µPD65006 / CF70043)	Donor board only	Semi-custom parts made for Psion.

Related pages

• Psion Organiser II
• Psion Organiser II General Maintenance
• Psion Organiser II Capacitor Replacement Guide
• Psion Organiser II Datapak Repair
• Psion Organiser II Spare Parts List
• Psion Organiser Troubleshooting Guide
• Battery Explosion, Capacitor or Corrosion Damage
• Capacitor Failure Symptoms