Editing Amstrad PC4386SX Troubleshooting Guide

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[[File:Amstrad PC4386SX showing CMOS battery failed.jpg|thumb|right|300px|A PC4386SX at the Centre for Computing History, showing "WARNING: CMOS battery failed" (photo: Centre for Computing History)]]
Fault-finding for the [[Amstrad PC4386SX]]. Amstrad's manuals for this model are not available online; the notes below draw on the messages the machine displays, Amstrad GmbH's notes on its self test, Cliff Lawson's link tables and owners' repair reports. Procedures are in the [[Amstrad PC4386SX Maintenance Guide]].<ref name="acme">acpc.me (ACME) archive, [https://acpc.me/ Amstrad PC section], directory DOCUMENTS_TECHNIQUES/SERVICE_MANUALS. Retrieved 2026-10-02. The PC3086/PC3286/PC3386SX, PC4386SX and PC5086/PC5286 service manuals are listed with placeholder images only, marked missing.</ref>

== Start-up ==

During the self test the BIOS prints a dot for each test passed. On the PC4386SX, alternating / and \ characters follow the third dot while the extended memory is tested, and the fourth dot appears when that test ends. The characters show that the test is still running.<ref name="amsline">"AMS-Line: Der Informationsdienst der Firma AMSTRAD", ''Amstrad PC International'' (page header ''CPC''), August/September 1991, p. 7. [https://archive.org/details/71_Amstrad_PC_International_1991-08-09 Internet Archive]. Retrieved 2026-10-02. Amstrad GmbH's column: the meaning of the start-up dots, the PC4386SX BIOS indicator, and the interrupt and I/O address tables of the PC3086, PC3286 and PC3386SX.</ref> Amstrad GmbH's key to the dots is in the [[Amstrad PC3086 Troubleshooting Guide#Start-up sequence|PC3086 guide]].

A PC4386SX in the Centre for Computing History shows these messages with an exhausted clock battery:<ref name="cch4386">Centre for Computing History, [https://www.computinghistory.org.uk/det/63138/ "Amstrad PC4386SX Computer"] (CH63138), 1991. Retrieved 2026-10-02. Photographs of a complete system showing "WARNING: CMOS battery failed".</ref>

<pre>
Please set user options
WARNING: CMOS battery failed
Press <CTRL-ALT-S> to run SETUP or any other key to continue
Insert a SYSTEM disk into drive A
</pre>

The wording matches the messages Amstrad documents for the PC3286 and PC3386SX, where "Please set user options" means invalid CMOS RAM contents and "Insert a SYSTEM disk into drive A" appears when no hard disk is configured.<ref name="cch4386" /><ref name="g3err">Amstrad plc, [[Amstrad PC3086, PC3286 and PC3386SX User Manual|''User Manual and MS-DOS Guide'' for the PC3086, PC3286 and PC3386SX]], 2nd ed. (1990), pp. 14-1 to 14-3. Non-fatal and fatal hardware error messages.</ref>

== Symptoms ==

{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''PC4386SX symptoms'''
! Symptom !! Likely cause !! Action
|-
| "WARNING: CMOS battery failed", setup and hard disk type lost || Exhausted battery inside the DS1287 clock module || Replace the module (a DS12887 has been used) and run SETUP with Ctrl-Alt-S<ref name="cch4386" /><ref name="vog4386rtc">Vogons forum, JidaiGeki's replies in [https://www.vogons.org/viewtopic.php?t=47162 "Amstrad 5086 - worth a go?"] (March 2016) and [https://www.vogons.org/viewtopic.php?t=102529 "Amstrad 3286"] (September 2024). Retrieved 2026-10-02. The PC4386SX's socketed Dallas clock module, replaced with a DS12887.</ref><ref name="lawat">Cliff Lawson (Amstrad plc), "Older AT PCs" (atpcs.htm), from his Amstrad support pages at web.ukonline.co.uk/cliff.lawson, as preserved at [http://www.freetimeweb.nl/home/computer/alt/lawsons-amstrad-computer_site/web.ukonline.co.uk/cliff.lawson/atpcs.htm freetimeweb.nl]. Retrieved 2026-10-02. SETUP on the 3xxx and 4xxx series, the BIOS 2.xx of the 3xxx series, memory links for the 3286, 3386SX and 4386SX, video DIP switches and option links.</ref>
|-
| "Insert a SYSTEM disk into drive A" on a hard disk machine || Hard disk type lost from the CMOS RAM || Run SETUP and set the drive type again<ref name="g3err" /><ref name="vog5086fd">Vogons forum, [https://www.vogons.org/viewtopic.php?t=74154 "AMSTRAD PC 5086 - Floppy Drive Problems"], Perro, tecnico, Jason_rg, flufetor, aotta69 and gca, May 2020 to August 2021. Retrieved 2026-10-02. Belt replacement on the original drives, a 26-pin to 34-pin adapter, capacitor failures in PC5286 power supplies and boards, and the PC4386SX power connector pinout.</ref>
|-
| Power LED on but no picture, with a replacement power supply || The +5&nbsp;V pin of the small connector SK106 must come up after the other rails || One owner got a picture only by applying +5&nbsp;V to SK106 pin 4 a second or two after switch-on<ref name="vog5086fd" />
|-
| Dead, original supply burned out || Power supply failure || One owner rebuilt the supply around a picoPSU; see the connector table in the maintenance guide<ref name="vog5086fd" />
|-
| Floppy drive does not read || Failed proprietary 26-way drive; new belts have not cured these || Fit a Gotek with FlashFloppy on a 26-way to 34-way adapter<ref name="vog5086fd" />
|-
| Hard disk very noisy || Original 80 MB drive worn || One owner reported his drive as extremely noisy; copy the data off before it fails<ref name="vogadlib">Vogons forum, [https://www.vogons.org/viewtopic.php?t=47900 "Amstrad Adlib Clone: Restoration and Testing"], brassicGamer and others, April 2016 to May 2017. Retrieved 2026-10-02. The Amstrad OPL2 sound card 3100-015P-4 bundled with the PC5286; gca reports the same card in his PC4386SX.</ref>
|-
| Serial mouse does not work || Built-in mouse interface still enabled || Remove the mouse interface link (LK20)<ref name="lawat" /><ref name="lawgen">Cliff Lawson (Amstrad plc), "General notes on Amstrad PCs" (general.htm), as preserved at [http://www.freetimeweb.nl/home/computer/alt/lawsons-amstrad-computer_site/web.ukonline.co.uk/cliff.lawson/general.htm freetimeweb.nl]. Retrieved 2026-10-02. Amstrad's proprietary keyboard and mouse interfaces up to the 4386, PS/2-compatible ones from the 5xxx series, and a summary specification of each PC.</ref>
|-
| Speaker too loud or too quiet || LK14 position || Pins 1 and 2 loud, pins 2 and 3 quiet<ref name="lawat" />
|-
| Memory errors after an upgrade || SIMMs not identical, or size and speed links wrong || Fit four identical 30-pin parity SIMMs and set LK27 to LK30 and LK25 and LK26<ref name="lawat" />
|}

== Final notes ==

* The machine in the Centre for Computing History has the 10-inch monitor, two speakers and an Amstrad joystick alongside the keyboard and mouse.<ref name="cch4386" />
* See also [[Capacitor Failure Symptoms]], [[Floppy Drive Repair]] and [[Hard Drive Maintenance and Repair]].

== References ==
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[[Category:Troubleshooting Guides]]