Editing Psion Series 3 General Maintenance

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[[File:Psion Series 3.jpg|thumb|420px|A Series 3. The case, hinges, button bar and battery arrangement are shared with the 3a, 3c and 3mx, so most maintenance is common to all four.]]

Preventive maintenance for the '''[[Psion Series 3]]''' (1991).

The Series 3 shares its case, hinges, button bar, keyboard construction and battery arrangement with the [[Psion Series 3a|3a]], [[Psion Series 3c|3c]] and [[Psion Series 3mx|3mx]]. '''The full common procedure is in the [[Psion Series 3a General Maintenance]] guide''' — this page covers what is specific to the original Series 3.

== ⚠️ Safety ==

No mains voltages. Two AA cells, and a '''+16 V Vh rail''' that appears at the SSD slots only when writing or formatting a Flash pack.<ref name="sibo">Psion PLC, ''SIBO Hardware Reference'', version 2.10, 3 February 1995, in the [https://doc.psion.info/books/the-psion-sibo-software-development-kit/page/hardware-reference Psion Documentation Project]. Source for the supply rails, the +16 V Flash programming rail, the timekeeping mechanism, the NMI sources and the power states.</ref> Everything is CMOS; use an anti-static strap.

== What is specific to the Series 3 ==

=== Timekeeping: take the clock seriously ===

'''This is the one maintenance difference that really matters.'''

The Series 3 has '''no hardware real-time clock'''. It keeps time by waking the CPU periodically — roughly every eight hours — to update the count. '''If the CPU cannot start because the main batteries are absent, the time is simply lost.'''<ref name="sibo" />

So on a Series 3, unlike a 3a:

* '''Do not store the machine with the AA cells out and expect the clock to survive.'''
* '''Change the AA cells promptly''' rather than leaving the machine running on backup.
* Expect to reset the clock after any extended storage, and check it after every battery change.

=== Backup cell ===

The Series 3 takes a '''CR1620''' lithium coin cell, as do the 3a and 3c. Replace it on a schedule rather than on failure — it is what holds your data during an AA change.<ref name="wp3">[https://en.wikipedia.org/wiki/Psion_Series_3 "Psion Series 3"], Wikipedia. Source for the backup cell types across the range and the documented clamshell problems.</ref>

=== Display ===

The Series 3 screen is '''240 × 80, black and white only''' — no grey plane and no backlight.<ref name="spec">[https://www.psion.netogram.com/psionspecifications.html "Psion specifications"], netogram.com. Source for the Series 3 screen dimensions and video memory access mode.</ref> It is a physically different panel from the 3a's and uses a different ribbon, so '''a 3a lid will not simply transplant onto a Series 3'''. Bear that in mind before buying a donor.

=== Sound ===

A '''piezoelectric buzzer''' driven directly from ASIC2, at high or low volume, and either by toggling a register bit or from the ASIC1 timer overflow.<ref name="sibo" /> There is no microphone and no sound recording — those arrived with the 3a. A Series 3 that will not record audio is not faulty.

=== Serial ===

9600 baud through the optional link pod, with the comms software held '''in the pod's own ROM''' rather than in the machine.<ref name="spec" /><ref name="wp3" /> A Series 3 that has "lost" its comms software has usually just lost its pod.

== Everything else ==

For the shared items — '''the battery lead, opening and closing the lid, the button bar, the SSD slots, the keyboard membrane, case cleaning and why the Series 3 family is not a recap candidate''' — see '''[[Psion Series 3a General Maintenance]]'''.

The single highest-value habit on any Series 3: '''open the lid squarely with two hands and stop at a comfortable angle'''. Over-opening is what shears the visible hinges.<ref name="mackay">David MacKay, [http://www.inference.org.uk/mackay/psion/psion9.html "Psion 3a Hinge breakages"]. Source for the over-opening failure mechanism.</ref>

== Preventive maintenance checklist ==

# Back up to an SSD or a PC.
# '''Note the time before, and reset it after, any battery work''' — this machine will lose it.
# Remove the AA cells for storage; check the compartment for corrosion.
# Replace the CR1620 if you do not know its age.
# Inspect the battery lead where it flexes, and re-seat the two-pin connector.
# Check all four hinges for cracks.
# Confirm the button bar sits flush and responds.
# Clean both SSD slots and confirm packs are recognised.

== Related pages ==

* [[Psion Series 3]] · [[Psion Series 3 Troubleshooting Guide]] · [[Psion Series 3 Hinge Repair]]
* [[Psion Series 3a General Maintenance]] — the shared procedure
* [[Battery Explosion, Capacitor or Corrosion Damage]] · [[Recommended Tools]]

== References ==

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[[Category:Psion]]
[[Category:Maintenance Guides]]