Amstrad PC4386SX Troubleshooting Guide
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.[1]
Start-up
[edit | edit source]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.[2] Amstrad GmbH's key to the dots is in the PC3086 guide.
A PC4386SX in the Centre for Computing History shows these messages with an exhausted clock battery:[3]
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
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.[3][4]
Symptoms
[edit | edit source]| 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[3][5][6] |
| "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[4][7] |
| Power LED on but no picture, with a replacement power supply | The +5 V pin of the small connector SK106 must come up after the other rails | One owner got a picture only by applying +5 V to SK106 pin 4 a second or two after switch-on[7] |
| Dead, original supply burned out | Power supply failure | One owner rebuilt the supply around a picoPSU; see the connector table in the maintenance guide[7] |
| 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[7] |
| Hard disk very noisy | Original 80 MB drive worn | One owner reported his drive as extremely noisy; copy the data off before it fails[8] |
| Serial mouse does not work | Built-in mouse interface still enabled | Remove the mouse interface link (LK20)[6][9] |
| Speaker too loud or too quiet | LK14 position | Pins 1 and 2 loud, pins 2 and 3 quiet[6] |
| 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[6] |
Final notes
[edit | edit source]- The machine in the Centre for Computing History has the 10-inch monitor, two speakers and an Amstrad joystick alongside the keyboard and mouse.[3]
- See also Capacitor Failure Symptoms, Floppy Drive Repair and Hard Drive Maintenance and Repair.
References
[edit | edit source]- ↑ acpc.me (ACME) archive, 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.
- ↑ "AMS-Line: Der Informationsdienst der Firma AMSTRAD", Amstrad PC International (page header CPC), August/September 1991, p. 7. 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.
- ↑ 3.0 3.1 3.2 3.3 Centre for Computing History, "Amstrad PC4386SX Computer" (CH63138), 1991. Retrieved 2026-10-02. Photographs of a complete system showing "WARNING: CMOS battery failed".
- ↑ 4.0 4.1 Amstrad plc, 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.
- ↑ Vogons forum, JidaiGeki's replies in "Amstrad 5086 - worth a go?" (March 2016) and "Amstrad 3286" (September 2024). Retrieved 2026-10-02. The PC4386SX's socketed Dallas clock module, replaced with a DS12887.
- ↑ 6.0 6.1 6.2 6.3 Cliff Lawson (Amstrad plc), "Older AT PCs" (atpcs.htm), from his Amstrad support pages at web.ukonline.co.uk/cliff.lawson, as preserved at 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.
- ↑ 7.0 7.1 7.2 7.3 Vogons forum, "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.
- ↑ Vogons forum, "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.
- ↑ Cliff Lawson (Amstrad plc), "General notes on Amstrad PCs" (general.htm), as preserved at 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.