Editing Psion Series 3mx

{{Infobox computer
| name         = Psion Series 3mx
| image        = [[File:Psion Series 3mx.jpg|250px]]
| caption      = A Psion Series 3mx
| developer    = Psion PLC
| manufacturer = Psion PLC
| type         = Clamshell palmtop / PDA
| release_date = July 1998
| discontinued = Final SIBO palmtop
| cpu          = NEC V30MX (80C86-compatible) @ 27.684 MHz
| memory       = 2 MB ROM; 1 MB or 2 MB RAM
| storage      = Two internal Solid State Disk (SSD) slots
| display      = 480 × 160 monochrome LCD, backlit on all models
| sound        = Microphone, loudspeaker and CODEC; 8 kHz 8-bit recording, DTMF auto-dialling
| dimensions   = 165 mm × 85 mm × 22 mm
| weight       = 275 g including batteries
| os           = EPOC16 (SIBO), with OPL
| predecessor  = [[Psion Series 3c]]
| successor    = [[Psion Revo]]
| model        = Matte silver metallic finish; CR2025 backup cell
}}
The '''Psion Series 3mx''', announced in July 1998, is the last and by a wide margin the fastest of the 16-bit SIBO palmtops. It is essentially an upgraded [[Psion Series 3c|Series 3c]] — same case, same screen, same applications — with a '''NEC V30MX running at 27.684 MHz''', roughly '''3.6 times the clock of the 3a and 3c'''.<ref name="wp3">[https://en.wikipedia.org/wiki/Psion_Series_3 "Psion Series 3"], Wikipedia. Source for the announcement date, the V30MX processor and clock speed, the RS-232 speed increase, the RAM options, the matte silver finish, the CR2025 backup cell, the universal backlight, the infrared port and the Easter egg.</ref>

It arrived '''after''' the 32-bit [[Psion Series 5]], as a last outing for the SIBO line rather than a replacement for it.<ref name="wp3" />

== What changed from the 3c ==

{| class="wikitable styled-table" style="width:70%; text-align:left;"
|+'''Series 3c → Series 3mx'''<ref name="wp3" /><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 ROM and RAM sizes, external power rating, backup cell, keyboard layout, CODEC sample rate and DTMF auto-dialling.</ref>
! Change !! Detail
|-
| '''Processor''' || '''NEC V30MX''' at '''27.684 MHz''', replacing the V30H at 7.68 MHz
|-
| '''ROM''' || 2 MB, up from 1 MB
|-
| '''Serial''' || '''Fast serial port, up to 115 kbit/s''' — roughly double the 3c
|-
| '''Backlight''' || '''All''' 3mx models are backlit, where the 3c's was a late and largely US option
|-
| '''Backup cell''' || '''CR2025''', not the CR1620 used by the Series 3, 3a and 3c
|-
| '''Finish''' || Matte '''silver metallic''' paint, against the 3c's dark grey
|-
| '''External power''' || 9 V, 250 mA
|-
| '''SSD door sensing''' || '''A pair of angled microswitches''', replacing the 3c's PCB tracks and door-hinge contact
|}

'''The backup cell change is the one to remember.''' A 3mx takes a '''CR2025''' and the earlier machines take a '''CR1620''' — different diameter and different thickness. Fitting the wrong one is a common and avoidable mistake.<ref name="wp3" />

Everything else carries over: the 480 × 160 screen, the 58-key keyboard with 9 touch-sensitive application keys, two internal SSD slots, an infrared port, 2 × AA cells and the same 165 × 85 × 22 mm case at 275 g.<ref name="spec" />

== Sound ==

The 3mx has a microphone, a loudspeaker and a CODEC giving digital recording and playback at '''8 kHz, 8 bits wide — 12 bits compressed to 8''' — plus DTMF auto-dialling through the speaker.<ref name="spec" />

== The SSD door microswitches ==

'''This is the 3mx's own characteristic fault, and it is worth understanding before you open one.'''

Where the [[Psion Series 3c|3c]] senses its SSD slot doors with PCB tracks and a small metal connector on the door hinge, the 3mx uses '''a pair of microswitches set at an angle'''.<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 failure mechanism, the "not ready" symptom, the requirement to repair both switches, and the repair method.</ref>

'''The plastic tips of those microswitch buttons snap off''' — almost always because the motherboard was prised out '''with the SSD doors closed'''. The machine then reports "'''not ready'''" and refuses to see a pack in either slot, which looks exactly like a motherboard fault and has sent more than one owner chasing the wrong thing.<ref name="rc3mx" />

'''Open both SSD doors before removing the mainboard.''' The repair, if it is already too late, is on the [[Psion Series 3mx Troubleshooting Guide]].

== Easter egg ==

The 3mx and the [[Psion Series 3c|3c]] contain a hidden melody and credits screen.<ref name="wp3" />

== Known problems ==

The family faults — '''hinge breakage''', '''button bar failure''', '''screen cable deterioration''' producing vertical lines<ref name="wp3" /> and the '''battery lead''' — plus the 3mx's own '''SSD door microswitches'''.

== General maintenance ==
{{Main|Psion Series 3mx General Maintenance}}

== Troubleshooting ==
{{Main|Psion Series 3mx Troubleshooting Guide}}

== Hinge repair ==
{{Main|Psion Series 3mx Hinge Repair}}

== See also ==

* [[Psion Series 3]] · [[Psion Series 3a]] · [[Psion Series 3c]] · [[Psion Siena]]
* [[Psion Revo]] — the 32-bit machine that took over the small-palmtop role
* [[Battery Refurbishment]]

== References ==

<references />

{{Navbox-Psion}}

[[Category:Psion]]