Amstrad PC2086 Maintenance Guide
Unlike the Amstrad PC1512 and Amstrad PC1640, the Amstrad PC2086 has its own power supply, a fan-cooled unit across the middle of the system unit, so the monitor can be serviced or replaced separately. The supply is adjusted with four presets against test points on its board; Amstrad's service manual gives the procedure, and treats the main CPU board and the drives as exchange items while allowing component-level repair of the monitors.[1]
Safety
[edit | edit source]Warning: the power supply runs from the mains. Its reservoir capacitor, C601 (150 µF 400 V), holds a dangerous charge after unplugging.
- Unplug the machine and discharge C601 before working on the supply board.[1]
- Fit a fuse of the same type: F601 is a 3.15 A time-lag 250 V fuse.[1]
- For the monitors Amstrad specifies a 1.5 kV RMS flash test for 3 s, more than 4 MΩ insulation resistance and no more than 0.5 Ω mains lead earth continuity after servicing.[1] Discharge a monitor's tube before working inside it; see CRT Discharge Procedure.
Opening the case
[edit | edit source]John Elliott describes the procedure:[2]
- Unplug the machine and remove any expansion cards.
- Remove the two screws at the front, the two at the back and the three where the expansion cards are fixed.
- Lift the top half. It is joined to the bottom half by the blue and black lead to the cells; unplug the in-line connector half way along it.
- To reach the main board, remove the supply: it is the metal box across the middle, held by two small screws at each end. Press the power switch in so that the supply lifts clear. The supply can stay connected to the main board unless a screw has fallen inside it.
Elliott warns that the four supply screws tend to fall into the supply or the case.[2]
Backup cells
[edit | edit source]The clock and configuration memory are kept by AA cells mounted on top of the base unit, under the monitor, and wired to the main board through the lead above.[3][2] Remove cells from a stored machine and clean any leakage with vinegar and then isopropyl alcohol; see Battery Explosion, Capacitor or Corrosion Damage. The PC2086 has no setup screen; after fitting new cells, set the floppy drive and display configuration with DEVICE.COM from the system disc.[4]
Power supply
[edit | edit source]Adjustment
[edit | edit source]Amstrad's alignment uses a digital voltmeter at four test points on the power board:[1]
| Rail | Test point | Preset | Setting |
|---|---|---|---|
| +5 V | A | VR604 | 5.15 V ±0.1 V |
| +12 V | B | VR603 | 12.15 V ±0.2 V |
| −5 V | C | VR601 | −5 V ±0.1 V |
| −12 V | D | VR602 | −12.00 V ±0.2 V |
The fifth step sets the +12 V protection: turn VR606 fully clockwise, short pins 1 and 3 of Q605 so that the protection cannot operate, connect an oscilloscope to the shorting link, adjust VR606 to obtain the waveform, and remove the link.[1][5]
Connectors
[edit | edit source]John Elliott, reading the supply schematic in his paper copy of the manual, gives the outputs as:[5]
| Connector | Pin 1 | Pin 2 | Pin 3 | Pin 4 | Pin 5 | Pin 6 |
|---|---|---|---|---|---|---|
| CD601 | +5 V | +5 V | 0 V | 0 V | 0 V | +12 V |
| CD602 | −5 V | 0 V | Not connected | −12 V | – | – |
CP603 carries +12 V and ground.[5] Measure the rails with the main board and drives connected: one owner measured 5.17 V but only 8.62 V on the 12 V output and −3.36 V on −5 V with the supply unloaded, on a machine that ran normally.[5]
Fan
[edit | edit source]The fan, M601, is the main source of noise. Owners replace it with a modern, quieter fan of the same size and voltage; read the label of the original before ordering.[5][6]
Drives
[edit | edit source]The floppy drive is a 3.5-inch 720 KB unit, listed as the A23M (FDD201); a socket on the side takes an external 5.25-inch drive.[1][7] See Floppy Drive Repair.
On the /30 the hard disc sits in a metal cage in the middle bay, with an RLL controller in an expansion slot. Elliott found the original controllers defective and describes replacing the drive with an 8-bit SCSI controller (a Future Domain TMC-885) and a SCSI disc, drilling new mounting holes in the cage.[8][7] Owners also fit XT-IDE CompactFlash cards; one ran his alongside the original controller, and another configures his cards for I/O address 380h and ROM address D8000h after a third owner's card froze the machine at start-up.[5] MS-DOS 3.3 handles partitions of up to 32 MB.[8] See Hard Drive Maintenance and Repair.
Key lock
[edit | edit source]The key lock switch (SW102) does not lock the case. Owners who find the machine stuck on a key lock fault open the case and disconnect the lock switch.[1][9]
Processor upgrade
[edit | edit source]The 8086 is the long chip second from the back in a group of four sockets on the left of the main board, under a metal sheet. An NEC V30 fits the same socket, with its notch to the left as seen from the front; with it, Windows 3.0's VGA driver works.[2] Lever the old chip out from each end in turn to avoid breaking its pins.[2]
Clock adjustment
[edit | edit source]The real-time clock is trimmed with TC101 against a timing meter on pin 21 of IC134, set to 0.2 s/day and adjusted to read 0.00.[1]
Related pages
[edit | edit source]- Amstrad PC2086 · Amstrad PC2086 Troubleshooting Guide · Amstrad PC2086 Capacitor Replacement Guide
- Amstrad PC2286 Maintenance Guide · Amstrad PC2386 Maintenance Guide
- Amstrad PC 2086 Service Manual
- Recommended Tools
References
[edit | edit source]- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Amstrad plc, PC2086 S/D/30 Personal Computer / PC12 MD / PC12 HRCD / PC14 CD / PC14 HRCD Monitors Service Manual. Hosted as File:Amstrad PC 2086 Service Manual.pdf, described at Amstrad PC 2086 Service Manual. Specification and safety tests p. 2; alignment instructions and notes to engineers p. 3; electrical parts list p. 4; power supply schematic p. 18.
- ↑ 2.0 2.1 2.2 2.3 2.4 John Elliott, "Replacing the PC2086 processor", seasip.info, 23 February 2013. Retrieved 2026-10-02. Case screws, the battery lead connector, removing the supply, the processor's position, fitting a V30.
- ↑ Wikipedia, "Amstrad PC2286" (revision 1353136875). Retrieved 2026-10-02. The PC2000 series, with BIOS settings backed by four AA cells on top of the base unit.
- ↑ John Elliott, "Amstrad XTs: Questions and answers", seasip.info, 26 June 2019. Retrieved 2026-10-02. DEVICE.COM for configuration on the PC2086, the V30 needed for Windows 3.0 colour drivers.
- ↑ 5.0 5.1 5.2 5.3 5.4 5.5 dorje, John Elliott, Ghislain and others, "Amstrad PC2086 PSU", Vintage Computer Federation Forums, June 2020 – November 2024. Retrieved 2026-10-02. John Elliott's transcription of the supply connectors CD601, CD602 and CP603 and the adjustment table from his paper service manual; an owner's unloaded readings; fan replacement; a supply that would not start after a full recap.
- ↑ Ghislain and dorje, "Amstrad PC2086", Vintage Computer Federation Forums, January 2025. Retrieved 2026-10-02. Community report: a PC2086 with rust and leaking capacitors, illegible board markings, the supply fan needing replacement.
- ↑ 7.0 7.1 John Elliott, "Amstrad XTs: Models", seasip.info, 19 April 2013. Retrieved 2026-10-02. The PC2086's three 3.5-inch bays, the external drive socket, the defective RLL controllers and hard cards.
- ↑ 8.0 8.1 John Elliott, "Replacing the PC2086 hard drive", seasip.info, 15 June 2004. Retrieved 2026-10-02. The hard disc cage in the middle bay, the SCSI replacement, partitions under MS-DOS 3.3 limited to 32 MB.
- ↑ cwathen, reply in "PC2086 advice", Vintage Computer Federation Forums, 19 August 2019. Retrieved 2026-10-02. Community comment: the "well known keylock issue" on the PC2086 and disconnecting the lock inside the case.