Amstrad PC5086 Maintenance Guide
.png)
The Amstrad PC5086 and Amstrad PC5286 share a case, keyboard, mouse, floppy drive type and user manual, but have different motherboards. The sections on safety, opening the case, the keyboard, the floppy drive and expansion cards apply to both models; the clock chip, links and hard disk notes are for the PC5086. The PC5286's memory, battery and links are in the Amstrad PC5286 Maintenance Guide, and faults are in the Amstrad PC5086 Troubleshooting Guide.[1][2] Amstrad's service manual for both models (reference 272826) has not been published online; the Centre for Computing History holds a paper copy.[3]
Safety
[edit | edit source]Warning: the power supply inside the system unit runs from the mains. Unplug the mains lead before removing the cover.
- Amstrad's manual warns of high voltage inside and requires the machine to be earthed. A UK plug on the mains lead must have a 5 A fuse. The supply voltage and frequency range are printed on the back panel.[4]
- The cooling vents are underneath the system unit. Do not stand it on papers or anything that blocks the air flow, and keep the space around it clear.[5]
- The monitor can be powered from the socket on the back of the system unit, so unplug the system unit before working on either.[5]
Opening the case
[edit | edit source]- Switch off and unplug the mains lead.
- Turn the system unit over and disconnect the keyboard and mouse, whose sockets are on the underside.[5][2]
- Undo the screws in the bottom panel.
- Turn the unit the right way up and slide the top cover forwards, off the machine.[6][2]
- Keep one hand on the metal cabinet while working on the board.[2]
Clock chip (CMOS RAM)
[edit | edit source]The PC5086 keeps the time, date and setup in a CMOS RAM chip with a built-in lithium battery. When the battery is exhausted the BIOS reports "System battery is dead - Replace and run SETUP". Amstrad's instruction is to replace the whole chip with the type it recommends, and it warns that trying to recharge the battery risks an explosion and that the old chip must not be put in a fire.[7][8]
Photographs of one PC5086 show the chip as a Dallas DS1287 real-time clock module. That machine had been modified by a previous owner to run its clock from two AA cells.[9] The same DS1287 is used in the Amstrad PC3086, where John Elliott replaced it with a DS12C887; his procedure is in the PC3086 guide.[10] After fitting a new chip, run SETUP (Ctrl-Alt-S during start-up) to set the time, date, drives and display.[11]
Option links
[edit | edit source].png)
| Link | Function | Source |
|---|---|---|
| LK1 | Fitted: built-in VGA enabled (default). Removed: VGA disabled, for a video card in a slot | User manual p. 11-8 |
| LK7 | Fitted: built-in hard disk interface enabled (hard disk models). Never fitted on floppy-only models | User manual p. 11-8 |
| LK2 | Connects pin 13 of the floppy connector to the controller's drive type input (dual-speed 5.25-inch drives) | Service manual, as read by Elliott |
| LK3 | Connects the same pin to the controller's alternative write precompensation input | Service manual, as read by Elliott |
| LK4 | Hard disk reset: pins 1 and 2 for a Seagate drive, pins 2 and 3 for other drives, open with no hard disk | Service manual, as read by Elliott |
| LK14 | Speaker volume: pins 1 and 2 loud, pins 2 and 3 quiet, no jumper for the volume wheel | Service manual, as read by Elliott |
Sources: Amstrad's user manual and John Elliott's notes from the service manual.[2][12]
Floppy drive
[edit | edit source]The drive is a Citizen unit with a single 26-way cable that carries both data and power; the PC5086 has one or two of them as standard 720 KB drives.[13][1] Owners report that the drives fail with age and that a new drive belt did not bring them back: one owner fitted new belts to two PC5086s, two PC5286s and a PC4386SX, and none worked reliably afterwards.[14]
A Vogons member wired an adapter from the 26-way connector to a standard 34-way drive with a separate power lead:[14]
| 26-way pin | Signal | 34-way pin |
|---|---|---|
| 1 | +5 V | Drive power |
| 2 | Index | 8 |
| 4 | Drive select A | 12 |
| 6 | Density | 2 |
| 8 | Ready | 34 |
| 10 | Motor on A | 16 |
| 12 | Direction | 18 |
| 14 | Step | 20 |
| 15 | Ground | Ground |
| 16 | Write data | 22 |
| 18 | Write enable | 24 |
| 20 | Track 0 | 26 |
| 22 | Write protect | 28 |
| 24 | Read data | 30 |
| 26 | Side select | 32 |
With this wiring and the drive type set in SETUP, the builder could use a 1.44 MB drive, but later found that the PC5086 booted and read the first disk without noticing a disk change, with or without pin 8 connected; another owner's similar adapter worked on a PC5286 but not on a PC5086. A third owner reported that a Gotek drive running FlashFloppy worked "flawless" with the same wiring on a PC4386SX.[14] Elliott's alternative is a floppy controller card in a slot; the BIOS disables the built-in controller when it detects one.[13][11]
See Floppy Drive Repair.
Hard disk
[edit | edit source]- The 40 MB drive is an XT-mode IDE drive. A replacement must work in XT mode, be half-height to fit the case, and take the small three-pin power connector.[13]
- Elliott notes that the original drive's jumpers can be set to AT mode to read it in a modern PC.[15]
- To use a different controller, remove LK7 to disable the built-in interface.[13][2]
- A second hard disk can only be a hard card in a slot, set up as drive D:.[16]
- The heads park automatically when the power is switched off, so no PARK program is needed before moving the machine. Let it reach room temperature after being somewhere cold.[7]
See Hard Drive Maintenance and Repair.
Co-processor and expansion cards
[edit | edit source]- An 8 MHz 8087 (8087-2) fits the empty socket on the motherboard. No SETUP change or link is needed.[6]
- The two half-length slots are 8-bit on the PC5086 and 16-bit on the PC5286. Amstrad's drawing gives 200 mm for a card in the top slot and 170 mm in the bottom slot.[2]
| Rail | Tolerance | Maximum current |
|---|---|---|
| +5 V | ±5% | 2 A |
| +12 V | ±5% | 0.5 A |
| −12 V | ±10% | 0.1 A |
| −5 V | ±10% | 0.1 A |
The tolerances give a quick check of the supply with a multimeter at a slot: +4.75 to +5.25 V and +11.4 to +12.6 V.[2]
Keyboard
[edit | edit source]The keyboard has an XT/AT switch on its back; it must be at XT for the PC5086 and at AT for the PC5286. A wrong setting gives "Keyboard error" at start-up.[5][8]
Capacitors
[edit | edit source]No capacitor values have been published for the PC5086's boards or power supply.[3][17] One owner's photographs show two large electrolytics, marked 4700 µF 6.3 V and 3300 µF, on a small board mounted on edge where the power leads enter, and the same owner reported that the capacitor at C50 on the motherboard looked damaged.[9] See Capacitor Failure Symptoms.
Related pages
[edit | edit source]- Amstrad PC5086 · Amstrad PC5086 Troubleshooting Guide
- Amstrad PC5286 Maintenance Guide · Amstrad PC4386SX Maintenance Guide
- Amstrad PC5086 and PC5286 User Manual
- Battery Explosion, Capacitor or Corrosion Damage · Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 1-3 to 1-4. Specifications of the PC5086 and PC5286.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 11-1 to 11-10. Expansion slots, slot power budget, and the option links of both models.
- ↑ 3.0 3.1 Centre for Computing History, "Amstrad PC5086 / PC5286 Service Manual" (CH27479): service manual for the PC5086, PC5286 and the PC14CDR, PC14HRCDR and PC14FMD monitors, reference 272826, 78 pages. Retrieved 2026-10-02.
- ↑ Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), p. 1-7. Mains plug, 5 A fuse, earthing, the high-voltage warning, and the supply rating on the back panel.
- ↑ 5.0 5.1 5.2 5.3 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 3-2 to 3-11. Ventilation, the XT/AT keyboard switch, monitor power socket, and start-up messages.
- ↑ 6.0 6.1 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 7-2 to 7-5. Fitting an 8087-2 or 80287-10 co-processor, opening the system unit, and expansion bus speeds.
- ↑ 7.0 7.1 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 13-2 to 13-3. Automatic head parking, the PC5086 CMOS RAM and the PC5286 Ni-Cad battery.
- ↑ 8.0 8.1 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 14-1 to 14-12. Troubleshooting and system messages.
- ↑ 9.0 9.1 Vogons forum, "Amstrad 5086 - worth a go?", gladders and others, March to September 2016. Retrieved 2026-10-02. Photographs of the inside of a PC5086, its Dallas DS1287 clock module modified to run from two AA cells, and a damaged capacitor at C50.
- ↑ John Elliott, "PC3086 clock chip replacement", seasip.info, 15 June 2004. Retrieved 2026-10-02. The CMOS battery warning, the DS1287 and its DS12C887 substitute, case removal and chip location.
- ↑ 11.0 11.1 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 4-2 to 4-25. SPEED, DISPLAY and MOUSE, SETUP (Ctrl-Alt-S or DOSETUP) and auto-configuration on both models.
- ↑ John Elliott, "PC5086 option links", seasip.info, 23 January 2004. Retrieved 2026-10-02. Links from the user manual and the service manual.
- ↑ 13.0 13.1 13.2 13.3 John Elliott, "Using normal peripherals on Amstrad XTs", seasip.info. Retrieved 2026-10-02. Floppy cables and drives, hard drives and keyboards for the PC3086 and PC5086.
- ↑ 14.0 14.1 14.2 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.
- ↑ John Elliott, "Using Amstrad XT peripherals on other machines", seasip.info. Retrieved 2026-10-02. Monitors, floppy and hard drives, keyboards and mice of the PC3086 and PC5086.
- ↑ Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 9-1 to 9-3. Hard disk compatibility and the PC5286 type table.
- ↑ 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.