Editing Psion Organiser II Troubleshooting Guide

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[[File:Psion Organiser II two-line and four-line models.jpg|thumb|420px|Establish which machine you have before you start. 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 in enough detail to diagnose this machine properly rather than by substitution.<ref name="tech2">''Psion Organiser II Technical Manual'', Psion Ltd, 1986, Chapter 2 "System Board", transcribed at [https://www.jaapsch.net/psion/tech02.htm Jaap's Psion Organiser II Page]. Source for the power-on and shutdown sequence, memory options and links, keyboard matrix, real-time clock divider chain, the 34 min 8 s wake-up, the LCD interface and the standby current figures.</ref><ref name="tech3">''Psion Organiser II Technical Manual'', Psion Ltd, 1986, Chapter 3 "Power Supply Board", transcribed at [https://www.jaapsch.net/psion/tech03.htm Jaap's Psion Organiser II Page]. Source for the rail voltages, operating states, currents, PP3 characteristics, the V_LCD generator, the 21 V programming pump and the LOWBAT detector.</ref> This page combines that with what the community has found in practice.

== ⚠️ Before you start ==

* '''Remove the battery before opening anything.'''
* '''Back up to a Datapak first if the machine still works at all.''' RAM contents do not survive a long battery removal.
* '''Never insert or remove a Rampak with the machine switched on.''' The sudden power drop corrupts data.<ref name="forum">[https://www.organiser2.com/ PSION Organiser II Forum]. Community source for the Rampak hot-plug corruption problem, top-slot device power behaviour, and general repair practice.</ref>
* Everything on the system board is CMOS. Use an anti-static strap.
* The '''SVPP rail reaches 21 V''' during Datapak writes, from a capacitor charged towards '''35 V'''. Harmless to you, fatal to a pack if applied at the wrong moment.

== Step 1: Identify the machine ==

If it powers up at all, get this out of the way first. From the main menu choose '''CALC''' and evaluate:<ref name="models">[https://www.jaapsch.net/psion/models.htm Psion Organiser II Models and Version Numbers], Jaap's Psion Organiser II Page. Source for the PEEKB identification values, the POS boot behaviour and the ROM version table.</ref>

* <code>PEEKB(-24)</code> — model: '''0''' = CM, '''1''' = XP, '''2''' = XP(LA), '''14''' = LZ, '''13''' = LZ64. Values of 17–20, 29, 30, 65, 66, 129 and 130 are POS and industrial variants.
* <code>PEEKB(-23)</code> — ROM version in BCD, so <code>$46</code> is version 4.6.
* <code>PEEKB(-25)</code> — language options.

This matters because the '''LZ/LZ64 use a Texas Instruments CF70043 control IC and HD66780/HD66100 LCD drivers''', while the earlier machines use an '''NEC µPD65006''' and '''HD44780/HD44100'''.<ref name="spares">''Psion Organiser II Spare Parts List v3'', Psion. Hosted on this wiki as [[:File:Psion Organiser II Spare Parts List v3.pdf]]. Source for the per-variant device identities, capacitor values, and part numbers.</ref> Boards are not interchangeable across that divide.

== Step 2: Rule out the four usual suspects ==

Before any measurement:

# '''Battery.''' Fit a known-good alkaline PP3 and check it under load, not just off-load. A cell that reads 9 V open-circuit and collapses under a 200 mA peak will produce completely misleading symptoms.
# '''Contrast.''' Sweep the thumbwheel through its full travel, slowly. On a tired display the usable band is narrow.
# '''Packs.''' Remove every pack and try again. A shorted or damaged pack can hold the whole machine down.
# '''AC key.''' If AC is dirty or dead, nothing will switch the machine on — it is the only key not in the scanned matrix.<ref name="tech2" />

== Step 3: Understand what should happen at switch-on ==

Knowing the sequence tells you where it stopped.<ref name="tech2" />

# Pressing '''AC''' (or 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.
# '''ON_B goes low immediately''', switching on the supply rail regulators.
# After a delay for the rails to settle, the processor is brought out of standby by sequencing '''STBY_B''' and '''RES_B''': it sits in reset for '''30 to 60 ms''' while the oscillator and E clock start, then runs.
# The processor initialises the LCD — the display drivers lose power when the machine is off, so the LCD is re-initialised every time.
# Shutdown is initiated by the processor itself, by accessing the SWITCH OFF address at <code>$01C0–$01FF</code>.

So: '''no rails at all''' is a power board or ON/OFF latch problem; '''rails present but no display''' is the processor, the ROM or the LCD; '''display but no response''' is the keyboard or the control IC.

== Step 4: Measure ==

=== Supply currents ===

The most informative single measurement is the current drawn from the battery.<ref name="tech3" />

{| class="wikitable styled-table" style="width:90%; text-align:left;"
|+'''Expected supply current'''<ref name="tech3" />
! State !! Expected !! What it means if wrong
|-
| '''Off''' || '''~40 µA''' total (30 µA system board plus ~10 µA power supply quiescent) || Milliamps here means something is leaking. A tired electrolytic on the power board is the usual cause, and it explains batteries flat after weeks in a drawer.
|-
| '''On, processor running''' || '''~25 mA''' || Much higher with no pack activity suggests a rail that is not regulating.
|-
| '''On, processor asleep''' || '''~4 mA''' || Never dropping to this suggests the machine is not entering sleep mode.
|-
| '''Slots active, no devices fitted''' || '''~25 mA''' internally || —
|-
| '''Slots active, peak''' || up to '''170 mA''' (regulator limit), system peaks '''200 mA''' || —
|}

Use a bench supply at 9 V with the '''current limit wound down to about 250 mA'''. A shorted rail then shows up as a limit rather than as damage.

=== Rail voltages ===

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Supply rails, and what a fault on each looks like'''<ref name="tech3" />
! Rail !! Off !! On !! Symptom when missing or wrong
|-
| '''VCC1''' || 3–5 V || '''5 V ±5 %''' || Nothing works. If it is present when off but absent when on, the main regulator has failed and the standby regulator is carrying the board.
|-
| '''VCC2''' || off || 5 V ±5 % || Display completely dead although the machine otherwise runs (beeps, responds to keys)
|-
| '''V_LCD''' || off || adjustable '''+1.2 V to −3 V''' by the thumbwheel || No contrast control at all; blank or washed-out display
|-
| '''SVCC''' || off || 5 V ±5 % when the slots are switched on || Packs not recognised at all
|-
| '''SVPP''' || off || '''4.5 V''' normally, '''21 V ±2 %''' pulsed while programming || Packs read fine but SAVE always fails
|}

Two useful behaviours to know:

* '''The main regulator gives up below about 5.3 V input''', after which VCC1 simply follows the supply about 0.3 V below it.<ref name="tech3" /> A machine that misbehaves on a half-flat battery is behaving as designed.
* '''LOWBAT is asserted when VCC1 falls about 2 % below nominal.'''<ref name="tech3" /> A persistent LOW BATTERY warning with a good cell points at the regulator or the divider chain that feeds the detector, not at the battery.

== Symptom table ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Psion Organiser II — fault symptoms'''
! Symptom !! Likely cause !! Action
|-
| '''Completely dead''' || Flat or high-resistance battery; corroded battery leads; AC key; ON/OFF latch; failed regulator || Known-good alkaline PP3 first. Then check for VCC1 present with the machine off. Then check AC reaches the control IC.
|-
| '''Dead, and the battery goes flat in storage''' || Leaky electrolytic on the power board || Measure the off-state current. It should be around 40 µA.
|-
| '''Black screen on first switch-on''' || Contrast at one extreme || Turn the thumbwheel. This is the single most common "fault" reported on these machines.<ref name="forum" />
|-
| '''Display blank but the machine beeps and responds''' || VCC2 or V_LCD missing || Measure both. VCC2 comes from VCC1 through a switch transistor; V_LCD comes from a charge pump.
|-
| '''No contrast change across the whole wheel travel''' || V_LCD charge pump or thumbwheel || Check the wheel's resistance changes; if it does, the pump has failed. See the [[Psion Organiser II Capacitor Replacement Guide]].
|-
| '''Missing dots, a dead column, a faded band''' || Conductive rubber LCD connector strip || Release the LCD clamp, clean both faces and the strip with isopropyl alcohol, reassemble squarely with even pressure. Replace the strip (Psion 3700 0002) if cleaning does not cure it.
|-
| '''Persistent whistle, buzz or squeal — especially on an LZ or LZ64''' || Ageing electrolytics on the power board. A '''10 µF capacitor whose positive side connects to the buzzer''' is the reported culprit, blocking the pulsing voltage of the programming pump || '''Recap the power board.''' This is a documented, confirmed fix.<ref name="bmv">Byte-My-Vdu, [https://bytemyvdu.wordpress.com/2018/12/14/psion-ii-lz-repair/ "Psion II LZ Repair"], 14 December 2018, and the comments beneath it. Source for the LZ/LZ64 whistle, the capacitor complement, the confirmation that a recap cures it, and the identification of the buzzer-connected 10 µF capacitor.</ref>
|-
| '''Clock resets or loses time on every battery change''' || Hold-up capacitor on the power board || Should hold the rail above 3 V for '''2–3 minutes''' with the machine off.<ref name="tech3" />
|-
| '''Clock drifts badly while the machine is off''' || 32768 Hz oscillator marginal, or the stage 2 counter || The machine wakes itself every '''34 min 8 s''' to update the clock; if that mechanism fails the time drifts.<ref name="tech2" />
|-
| '''Machine switches itself on in a drawer''' || Normal || It wakes every 34 min 8 s to keep time, then switches off again.<ref name="tech2" />
|-
| '''One key dead''' || Keymat pill or PCB pad || Clean both. See [[Psion Organiser II General Maintenance]].
|-
| '''A whole row of keys dead''' || One of the K1–K7 outputs || Those outputs come from the control IC's stage 2 counter bits. Check for a broken track first.<ref name="tech2" />
|-
| '''A whole column of keys dead''' || One of the KBD1–KBD5 inputs on port 5 bits 2–6 || Trace the line back to the processor.<ref name="tech2" />
|-
| '''AC dead, everything else fine''' || AC key contact || AC is wired directly to the control IC and to port 5 bit 7, outside the scanned matrix.<ref name="tech2" />
|-
| '''Packs read but SAVE always fails''' || 21 V programming pump || The pump storage capacitor is the usual failure. Reads do not use it, which is why the fault is so clean-cut.
|-
| '''Packs not recognised at all''' || SVCC not switched on; slot contacts; PACON_B || Clean the contacts, then check 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 slots to confirm before opening anything.
|-
| '''Rampak has lost its contents''' || Flat backup cell in the pack, or hot-plugging || Check the pack's own cell. Never hot-plug a Rampak.<ref name="forum" />
|-
| '''"DATAPAK FULL" on a pak that looks empty''' || Erased records still occupy space || Normal EPROM behaviour. Copy the live records to a fresh pak, or have the old one UV-formatted.
|-
| '''Machine shows "PACK?" or "INSERT PACK?" then switches off''' || '''It is a POS model''' || Not a fault. POS machines look for a procedure called BOOT on the fitted packs and switch off if they cannot find one.<ref name="models" />
|-
| '''Numeric keypad or unusual keyboard legends''' || POS variant || Confirm with <code>PEEKB(-24)</code>.<ref name="models" />
|-
| '''Persistent LOW BATTERY with a good cell''' || Regulator or the LOWBAT divider chain || LOWBAT trips at about 2 % below nominal VCC1.<ref name="tech3" />
|-
| '''Corrosion on the boards, green vias''' || Past battery leak or capacitor leakage || Neutralise, clean thoroughly and inspect every track in the affected area. See [[Battery Explosion, Capacitor or Corrosion Damage]].
|-
| '''Buzzer clicks but will not produce a tone''' || Control IC or software, not the element || The element only makes a sound on ''transitions'' of the ALARM signal; a tone is the software toggling it.<ref name="tech3" />
|}

== Diagnosing the memory configuration ==

If a machine boots but reports the wrong amount of memory, or crashes in a way that suggests a decoding problem, check the '''memory decode links'''. There are eight, arranged as four pairs, and '''only one of each pair should be fitted'''.<ref name="tech2" />

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Correct link options'''<ref name="tech2" />
! Version !! PROM !! RAM !! Links fitted
|-
| CM || 32 KB at <code>$8000–$FFFF</code> || 8 KB at <code>$2000–$3FFF</code> || L1, L4, L5, L7
|-
| XP || 32 KB at <code>$8000–$FFFF</code> || 8 KB + 8 KB at <code>$2000–$5FFF</code> || L1, L4, L5, L7
|-
| LA || 32 KB at <code>$8000–$FFFF</code> || 32 KB at <code>$0400–$7FFF</code> || L1, L4, L6, L7
|}

The individual links do the following:<ref name="tech2" />

* '''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 be '''250 ns or better'''.<ref name="tech2" /> The 32 KB parts Psion used are '''62256LFP / KM62256BLG''' and the 8 KB parts '''6264LFP'''.<ref name="tech2" /><ref name="spares" />

== What is realistically repairable ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
! Part !! Repairable? !! Notes
|-
| '''Power supply board''' || '''Yes''' || Mixed technology, but the electrolytics are leaded and the values are published. This is where most faults are.
|-
| '''LCD connector strip''' || '''Yes''' || Cleaning usually does it; replacements exist (Psion 3700 0002).
|-
| '''LCD panel''' || Yes, with a donor || Psion part 3900 0003. Note the LZ uses different drivers.
|-
| '''Keymat''' || '''Yes''' || Washable; Psion part 8700 0001.
|-
| '''RAM / PROM''' || Yes, for SMD-capable hands || 62256/6264 static RAM and 27C256/27C64 EPROM are all standard parts, and Organiser II ROM images are archived.
|-
| '''HD6303XFP processor''' || Difficult || 80-pin flat pack. Obtainable but a demanding rework job.
|-
| '''Control IC (µPD65006 / CF70043)''' || '''No''' || Semi-custom parts made only for Psion. A failed control IC means a donor board.
|-
| '''Board with heavy corrosion''' || Depends || Track repair is possible but the boards are thin and the tracks fine.
|}

== Related pages ==

* [[Psion Organiser II]]
* [[Psion Organiser II General Maintenance]]
* [[Psion Organiser II Capacitor Replacement Guide]]
* [[:File:Psion Organiser II Spare Parts List v3.pdf|Organiser II Spare Parts List]]
* [[Psion Organiser Troubleshooting Guide]] — the Series 1
* [[Battery Explosion, Capacitor or Corrosion Damage]] · [[Capacitor Failure Symptoms]]

== References ==

<references />

{{Navbox-Psion}}

[[Category:Psion]]
[[Category:Troubleshooting Guides]]