Amstrad PC3286 Maintenance Guide
The Amstrad PC3286 and Amstrad PC3386SX use the same main board with different processor daughterboards, and Amstrad's user manual gives one set of option links for both. The sections below cover that board: the daughterboard, memory, cache, links, video switches and drives. Safety, opening the case, the clock chip and head parking are the same on all three Generation 3 models and are described in the Amstrad PC3086 Maintenance Guide. Model-specific points for the 386SX are in the Amstrad PC3386SX Maintenance Guide, and faults in the Amstrad PC3286 Troubleshooting Guide.[1][2] Amstrad's service manual (SM-PC3000) has not been published online.[3]
Before starting
[edit | edit source]- Follow the safety notes and the lid procedure in the PC3086 guide: unplug the machine, check the voltage selector, slide the lid forward about three inches only and rest it on the front panel.[1]
- Keep one hand on the metal cabinet while working on the board.[1]
- After changing memory, the co-processor or the video adaptor, run SETUP so that the CMOS RAM matches the hardware.[4]
Processor daughterboard and co-processor
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The co-processor socket is on the processor daughterboard: an 80287 on the PC3286, an 80387SX on the PC3386SX. No links need changing.[2]
- Open the system unit.
- Remove the daughterboard from its connector on the main board.
- Fit the co-processor in the empty socket on the daughterboard.
- Refit the daughterboard carefully, close the case and record the co-processor in SETUP.[2][4]
The PC3286 board seen on Vogons is marked MS0188A, "286", "Amstrad copyright 1990" and Z70922.[5]
Memory
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Memory goes in four SIMM sockets on the main board, to a maximum of 16 MB. A 256 KB SIMM holds nine bits per byte, the ninth for parity, and may be built from nine 256 Kbit chips or from two 1 Mbit chips and one 256 Kbit chip.[6]
- The PC3286 takes one or two pairs. A single pair goes in the outer two sockets (SKT156).
- The PC3386SX must have four identical SIMMs, giving 1, 4 or 16 MB, because it reads memory 32 bits wide.
- Set links LK19 to LK22 for the total fitted, and LK23 and LK24 for the slowest SIMM.[6]
| Total | SKT156 | SKT157 | LK22 | LK21 | LK20 | LK19 |
|---|---|---|---|---|---|---|
| 512 KB | 2 × 256 KB | Empty | In | In | In | Out |
| 640 KB | 2 × 256 KB | 2 × 64 KB | In | In | Out | In |
| 1 MB* | 2 × 256 KB | 2 × 256 KB | In | In | Out | Out |
| 2 MB | 2 × 1 MB | Empty | In | Out | Out | In |
| 2.5 MB | 2 × 256 KB | 2 × 1 MB | Out | In | In | In |
| 4 MB* | 2 × 1 MB | 2 × 1 MB | Out | In | In | Out |
| 8 MB | 2 × 4 MB | Empty | Out | In | Out | Out |
| 16 MB* | 2 × 4 MB | 2 × 4 MB | Out | Out | Out | Out |
* The only sizes allowed on the PC3386SX.[6]
| DRAM speed | LK23 | LK24 |
|---|---|---|
| 80 ns | Out | Out |
| 100 ns | In | Out |
| 120 ns | Out | In |
| 150 ns | In | In |
Cliff Lawson of Amstrad confirms that the PC3286 and PC3386SX use the same memory links as the PC2386, with the PC3286 also taking the intermediate sizes.[7]
To fit a SIMM, insert it into the socket at about 45° and turn it upright, as Amstrad's drawing shows. With the case closed, switch on and run SETUP to set the base and extended memory; extended memory is set in 64 KB steps, and what is left over is available as LIM expanded memory through MEMM.SYS.[6][4][8]
Cache
[edit | edit source]Amstrad lists 64 KB of 35 ns cache RAM as optionally fitted; where the cache sockets are empty, chips can be added. Links LK42 and LK37 are both in for 35 ns chips. LK36 sets whether memory on expansion cards is cached; turn it off if a card with bank-switched memory, such as a LIM expanded memory card, is fitted. The DEVICE command shows and changes which areas are cached.[6][1][9]
Option links
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| Link | Out (no jumper) | In (jumper fitted) |
|---|---|---|
| 9, 10, 11, 12 | Mouse interrupt; fit one only: LK9 IRQ 5 (default), LK10 IRQ 4, LK11 IRQ 9, LK12 IRQ 3 | |
| 13 | 256 KB base memory when LK29 is out | 512 KB base memory when LK29 is out |
| 14 | External video adaptor is monochrome (built-in VGA disabled) | External video adaptor is colour |
| 17, 18 | Do not change | |
| 19 to 22 | Memory size; see the table above | |
| 23, 24 | DRAM speed; see the table above | |
| 25, 26 | Do not change; pins 1 and 2 | |
| 27 | On-board hard disk adaptor disabled | Enabled |
| 28 | On-board VGA disabled | Enabled |
| 29 | Base memory as set by LK13 | 640 KB base memory |
| 30 | Mouse adaptor disabled | Enabled |
| 31 | Parallel port disabled | Enabled |
| 32 | Floppy controller disabled | Enabled |
| 33 | Serial port (COM1) disabled | Enabled |
| 34 | Power-on self test disabled | Enabled |
| 36 | Cache on expansion bus disabled | Enabled |
| 37, 42 | Cache RAM is 35 ns; do not change | |
| 38, 41, 43, 47 | Do not change; pins 1 and 2 | |
| 500, 501 | Do not change; pins 1 and 2 on the PC3386SX (if present), pins 2 and 3 on the PC3286 | |
| 720 | PC3386SX daughterboard: pipelining disabled | Pipelining enabled |
Amstrad describes LK34 as for engineering diagnostics and advises users not to change it. The base memory and video links (LK13, LK14, LK29) only matter when the CMOS RAM is blank, for example just after a new clock chip.[1] Lawson's list of links for the "1/2/3xxx" machines uses the same numbers for the built-in devices.[7]
To use a serial mouse in place of the Amstrad mouse, remove LK30 to disable the built-in mouse adaptor; Lawson notes that the /C switch of MOUSE.COM is not enough on its own.[10][1]
Video DIP switches
[edit | edit source]| Switch | On | Off |
|---|---|---|
| 1 | Multi-frequency monitor attached | Fixed-frequency VGA monitor (default) |
| 2 | PS/2 mode (default) | AT mode |
| 3 | Reserved | |
| 4 | 16-bit bus interface to the VGA | 8-bit bus interface |
Amstrad's manual says switch 4 is normally on, but the same paragraph calls 8-bit mode the default, chosen for compatibility; 16-bit mode can be faster. Lawson suggests switches 1, 2 and 4 on.[11][7]
Drives
[edit | edit source]- The built-in hard disk adaptor is AT-type IDE. SETUP holds the drive type; the 40 MB drive is type 17 in Amstrad's example, and types 50 and 51 are user-defined for drives not in the table on pp. 9-2 to 9-3.[12][4]
- Park the heads with PARK.COM before moving the machine (see the PC3086 guide).[13]
- A 3.5-inch 1.44 MB or 5.25-inch 1.2 MB floppy drive was fitted as standard; the internal cabling supports two floppy drives and two IDE hard disks.[9]
- LK27 disables the on-board hard disk adaptor and LK32 the floppy controller, for use with controllers in expansion slots.[1]
See Hard Drive Maintenance and Repair and Floppy Drive Repair.
Capacitors
[edit | edit source]No capacitor values have been published for this board or its power supply: the service manual is not online and no community recap list exists.[3][14] See Capacitor Failure Symptoms.
Tools
[edit | edit source]- Cross-head screwdrivers and an anti-static strap
- Jumper links, and SIMMs of the speed set on LK23 and LK24
- Digital multimeter
- See Recommended Tools.
Related pages
[edit | edit source]- Amstrad PC3286 · Amstrad PC3286 Troubleshooting Guide
- Amstrad PC3086 Maintenance Guide · Amstrad PC3386SX Maintenance Guide
- Amstrad PC3086, PC3286 and PC3386SX User Manual
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 11-1 to 11-10. Expansion slots, opening the lid, and the option link tables for the PC3086 and for the PC3286 and PC3386SX.
- ↑ 2.0 2.1 2.2 Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 7-1 to 7-7. Processor speeds, fitting an 8087, 80287 or 80387SX co-processor, and opening the system unit.
- ↑ 3.0 3.1 Centre for Computing History, "Amstrad PC3086 PC3286 PC3386SX Colour Personal Computers Service Manual" (CH27476): 53-page service manual with schematics and wiring diagrams, reference SM-PC3000. Retrieved 2026-10-02.
- ↑ 4.0 4.1 4.2 4.3 Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 3-7 to 3-15. Voltage selector, power switch, the "Please wait." self-test dots, start-up messages and BIOS versions, and the SETUP program for the PC3286 and PC3386SX.
- ↑ Vogons forum, "Amstrad 3286", tarasque and others, September 2024 to February 2025. Retrieved 2026-10-02. A PC3286 that would not POST after the Dallas clock module was replaced with a Necroware nwX287; the owner's list of option link positions; photographs (CC BY 4.0).
- ↑ 6.0 6.1 6.2 6.3 6.4 Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 8-6 to 8-10. Memory cache, SIMM upgrades, memory size and DRAM speed links, cache speed links.
- ↑ 7.0 7.1 7.2 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.
- ↑ Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 4-2 to 4-18. The DEVICE command: display, floppy drive, cache, memory map and processor speed settings.
- ↑ 9.0 9.1 Amstrad plc, PC3286 leaflet, © August 1990, p. 2 (specification). Hosted as File:Amstrad PC3286 leaflet (1990).pdf.
- ↑ 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.
- ↑ Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 6-5 to 6-15. PS/2 and AT video modes, disabling the built-in VGA, links 901 and 902, and the video DIP switches.
- ↑ Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 9-1 to 9-3. Built-in IDE adaptors (XT type on the PC3086, AT type on the PC3286 and PC3386SX) and the hard disk type table.
- ↑ Amstrad plc, User Manual and MS-DOS Guide for the PC3086, PC3286 and PC3386SX, 2nd ed. (1990), pp. 13-2 to 13-4. Transporting a hard disk PC, PARK.COM, and replacing the CMOS RAM.
- ↑ 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.