https://wiki.retrotechcollection.com/index.php?action=history&feed=atom&title=Psion_Series_3mx_General_MaintenancePsion Series 3mx General Maintenance - Revision history2026-09-11T07:11:22ZRevision history for this page on the wikiMediaWiki 1.46.0https://wiki.retrotechcollection.com/index.php?title=Psion_Series_3mx_General_Maintenance&diff=11738&oldid=prevJosh: Create Psion page set: researched from Psion manuals, service documentation and community repair sources2026-09-08T22:54:42Z<p>Create Psion page set: researched from Psion manuals, service documentation and community repair sources</p>
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[[File:Psion Series 3mx.jpg|thumb|420px|A Series 3mx. Two things set its maintenance apart from the rest of the family: the CR2025 backup cell, and the SSD door microswitches that break if you open the machine carelessly.]]<br />
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Preventive maintenance for the '''[[Psion Series 3mx]]''' (1998).<br />
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The 3mx shares its case, hinges, button bar, keyboard and battery arrangement with the rest of the Series 3 family. '''The full common procedure is in [[Psion Series 3a General Maintenance]]''' — this page covers what is specific to the 3mx.<br />
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== ⚠️ The one rule for this machine ==<br />
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'''OPEN BOTH SSD DOORS BEFORE LIFTING THE MAINBOARD.'''<br />
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The 3mx senses its SSD slot doors with '''a pair of microswitches set at an angle'''. Prising the motherboard out with the doors shut '''snaps the plastic tips off those switches''', after which the machine reports "not ready" and will not see a pack in either slot.<ref name="rc3mx">Richard Zealley, [https://www.retrocoding.uk/psion-3mx-ssd-microswitch-repair/ "Psion Series 3mx SSD door microswitch repair"], Retro Coding, 25 May 2020. Source for the microswitch arrangement, the damage mechanism, the symptom, the need to repair both switches and the repair method.</ref><br />
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It is a self-inflicted fault, it is entirely avoidable, and it is the single most useful thing to know about working on a 3mx.<br />
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== The backup cell is different ==<br />
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'''The 3mx takes a CR2025.''' The [[Psion Series 3|Series 3]], [[Psion Series 3a|3a]] and [[Psion Series 3c|3c]] all take a '''CR1620'''.<ref name="wp3">[https://en.wikipedia.org/wiki/Psion_Series_3 "Psion Series 3"], Wikipedia. Source for the CR2025 backup cell on the 3mx and CR1620 on the earlier models, the universal backlight and the fast serial port.</ref><br />
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A CR1620 is 16 mm across and 2.0 mm thick; a CR2025 is 20 mm across and 2.5 mm thick. They are not interchangeable, and a machine that will not hold data through a battery change may simply have the wrong cell wedged in the holder.<br />
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Replace it on a schedule rather than on failure.<br />
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== Backlight ==<br />
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'''Every 3mx is backlit.'''<ref name="wp3" /> That is a change from the 3c, where the backlight was a late and largely US-market option.<br />
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The practical consequence is battery life: the backlight is the largest discretionary load in the machine. Before investigating a "3mx eats batteries" complaint, '''check the backlight is not simply being left on'''.<br />
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== Serial and infrared ==<br />
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* The 3mx has a '''fast serial port, up to 115 kbit/s''', double the 3c's.<ref name="wp3" /><br />
* '''The connector matches the 3c and the [[Psion Siena|Siena]], not the 3 or 3a.''' Travel Modem connections also differ between the 3/3a and 3c/3mx pairs.<ref name="wp3" /><br />
* Keep the infrared window clean and unscratched, and the serial connector covered when not in use.<br />
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== Batteries ==<br />
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2 × AA cells, a '''CR2025''' backup cell and a '''9 V, 250 mA''' external supply — note the higher current rating than the 3a and 3c's 150 mA.<ref name="spec">[https://www.psion.netogram.com/psionspecifications.html "Psion 3mx, Psion 5, Psion 5mx, Psion Revo and Psion Revo Plus specifications"], netogram.com. Source for the 3mx external power rating, backup cell and CODEC specification.</ref><br />
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'''The battery lead is still the fault that eats cells''' on any Series 3 — see [[Psion Series 3a General Maintenance]].<br />
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== Case ==<br />
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The 3mx has a '''matte silver metallic paint''' finish rather than the [[Psion Series 3c|3c]]'s rubberised soft-touch coating.<ref name="wp3" /> That is good news: '''the 3mx does not suffer the 3c's sticky-case problem'''.<br />
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Clean it with a barely damp cloth. Painted finishes mark, so avoid solvents — including the isopropyl alcohol used to strip a 3c.<br />
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== Capacitors ==<br />
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'''Not a recap candidate.''' See the reasoning in [[Psion Series 3a General Maintenance]].<br />
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== Preventive maintenance checklist ==<br />
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# Back up to an SSD or a PC.<br />
# '''Confirm the backup cell is a CR2025''', and replace it if you do not know its age.<br />
# Inspect the battery lead and re-seat the two-pin connector.<br />
# Check both SSD door microswitches operate cleanly and that packs are recognised in both slots.<br />
# Check all four hinges.<br />
# Confirm the button bar sits flush and responds.<br />
# Check the backlight works, and that it is not being left on.<br />
# Clean the infrared window and the serial connector.<br />
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== Related pages ==<br />
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* [[Psion Series 3mx]] · [[Psion Series 3mx Troubleshooting Guide]] · [[Psion Series 3mx Hinge Repair]]<br />
* [[Psion Series 3a General Maintenance]] — the shared procedure<br />
* [[Battery Explosion, Capacitor or Corrosion Damage]] · [[Recommended Tools]]<br />
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== References ==<br />
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<references /><br />
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{{Navbox-Psion}}<br />
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[[Category:Psion]]<br />
[[Category:Maintenance Guides]]</div>Josh