Amstrad PC5086 Troubleshooting Guide
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Fault-finding for the Amstrad PC5086. Amstrad's user manual covers the PC5086 and Amstrad PC5286 together, and its tables of start-up messages are reproduced here for both models, with the PC5286-only messages marked. The PC5286's own faults are in the Amstrad PC5286 Troubleshooting Guide, and the procedures referred to below are in the Amstrad PC5086 Maintenance Guide.[1] No service manual, test points or voltage tables are available online for either model.[2]
Start-up
[edit | edit source]During the self test the PC5086 shows its BIOS version and memory, and offers SETUP for about ten seconds:[3]
Amstrad PC5086 - BIOS VERSION AM50 v.xxx 0640K RAM passed Self tests in progress, Please Wait... To configure the system with SETUP, press CTRL-ALT-S now
With an unprepared hard disk it then reports:[4]
AMSTRAD PC5086 Self test and Initialisation in Progress, Please Wait... XT Hard Disk BIOS Revision 2.0 Disk Boot Failure - Press any key to retry
| Symptom | Action |
|---|---|
| Nothing happens at all | Check the mains socket with a lamp, then the wiring and fuse of the PC's mains plug |
| The PC asks for a System disk | Check the disk and reset; if it asks again, the disk is damaged or has no system on it, or the drive heads need cleaning. Run CHKDSK on the disk afterwards |
| The PC does not respond to the keyboard, cursor flashing | Check the keyboard plug on the underside of the system unit; switch off, wait and switch on again |
| No cursor, system locked | Reset with Ctrl-Alt-Del from a system disk; if that fails, switch off and start again |
| Keys produce the wrong characters | KEYB from a different version of DOS is loaded; boot from the PC's own system disk |
| No beep when a disk cannot be read | Turn up the volume control |
Source: Amstrad's troubleshooting chapter.[1]
Non-fatal messages
[edit | edit source]| Message | Meaning and action |
|---|---|
| Keyboard error | A key is held down, the cable is not plugged in properly, or the switch on the back of the keyboard is wrong: XT for the PC5086, AT for the PC5286 |
| Real time clock error | The time and date in the CMOS RAM are invalid |
| System CMOS checksum bad - Run SETUP; Extra-CMOS checksum bad - Run SETUP | The CMOS RAM contents are invalid; press F2 for SETUP or F1 to continue |
| System battery is dead - Replace and run SETUP | PC5086: the lithium battery inside the CMOS RAM is exhausted; replace the complete chip |
| System battery has discharged - Run SETUP | PC5286: the Ni-Cad battery has run down; leave the PC switched on for about 16 hours to recharge it |
| Diskette error or non system disk / Please insert bootable diskette and press any key | No hard disk fitted; on a PC5286 it can also mean that the CMOS RAM holds the wrong hard disk type |
| Bad diskette boot record or corrupted disk | The boot disk is corrupt |
| Memory size does not match CMOS - Run SETUP | Check the memory settings in SETUP |
| Coprocessor internal register error | The co-processor is faulty or not fitted properly |
| External COM (or LPT) port detected, internal port configured as COMn (or disabled) | A port card has been fitted and the built-in port has been moved; press F1 within 8 seconds to confirm |
Source: Amstrad's message list.[1]
Fatal errors
[edit | edit source]Amstrad's advice for these is to switch off for a few seconds and on again, and to note the message if it returns.[1]
| Message | Notes |
|---|---|
| Keyboard controller error; Keyboard interface error | |
| Fixed Disk 0 Failure; Fixed Disk 1 Failure; Fixed Disk Controller Failure | Hard disk or interface fault; LK7 must be fitted on hard disk models[5] |
| xxxxxK RAM Failed at offset: xxxx; System, Shadow or Extended RAM Failed at offset | Memory fault (Shadow and Extended RAM are PC5286 only) |
| Monochrome adapter error; Color graphics adapter error | Video fault; LK1 disables the built-in VGA so that a card can be tried[5] |
| Diskette drive failure on drive A (or B) | See the floppy drive notes below |
| System timer error |
Owner reports
[edit | edit source]| Symptom | Findings |
|---|---|
| Floppy drive will not read, or reads one directory and then fails | Drives of this type failed on two PC5086s, two PC5286s and a PC4386SX belonging to one owner, and new belts did not cure them. A standard drive on an adapter booted but missed disk changes on a PC5086; a Gotek with FlashFloppy worked on a PC4386SX[6] |
| "Invalid" boot disk with a standard drive on an adapter | Reported on a PC5086 with both a PC drive and an Amiga drive that drives the Ready line; the same adapter worked on a PC5286[6] |
| No picture and no start-up beeps after the clock batteries were removed | One owner removed the AA cells from a modified clock module and the machine stopped showing anything; the thread records no fix. A reply suggested fitting fresh cells as the first test[7][8] |
| A PS/2 keyboard from another PC does not work | The PC5086 needs XT signalling through its PS/2-shaped socket; use a keyboard with an XT mode, such as the Amstrad keyboard switched to XT[8][9][4] |
Final notes
[edit | edit source]SPEED 4slows the PC5086 to 4.77 MHz for software that runs too fast;SPEED 8restores it.[3]- To display CGA, EGA, MDA or Hercules software, use the DISPLAY command (C, E, M, H or F).[3]
- See also Capacitor Failure Symptoms, Floppy Drive Repair and Hard Drive Maintenance and Repair.
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 Amstrad plc, PC5086 and PC5286 User Manual and Guide to MS-DOS (1991), pp. 14-1 to 14-12. Troubleshooting and system messages.
- ↑ 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.
- ↑ 3.0 3.1 3.2 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.
- ↑ 4.0 4.1 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.
- ↑ 5.0 5.1 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.
- ↑ 6.0 6.1 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 PC-5086 no image on monitor?", gladders, August 2016. Retrieved 2026-10-02.
- ↑ 8.0 8.1 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, "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.