Amstrad PPC640 Maintenance Guide
The Amstrad PPC640 is a 1987 portable that runs from ten C cells, an external 12 V adaptor or an Amstrad monitor, so most of its routine care concerns the batteries and the power input. Amstrad expected dealers to diagnose faults with its R.P.5-2 diagnostic tool and to exchange whole boards, disc drives and the LCD. The service manual still gives the schematics, the parts lists and two alignment steps.[1] Faults are covered in the Amstrad PPC640 Troubleshooting Guide and the electrolytic capacitors in the Amstrad PPC640 Capacitor Replacement Guide.
Batteries
[edit | edit source]| Item | Detail |
|---|---|
| Cells | Ten alkaline C cells, five in each of two tubes |
| Running time | Up to 8 hours (Amstrad's specification) |
| Not recommended | Zinc-carbon (cannot supply the current) and NiCd (lower voltage, early low-battery warnings) |
| Battery lid | Part 177222 (PPC640); 177221 (PPC512) |
- Load five cells into each tube with the positive end towards the plus sign on the holder.
- Insert the tubes into the compartment in the bottom of the machine and refit the lid.
- Take the tubes out to change the cells and keep them; Amstrad says they reduce the risk of the power dropping out if the machine is jolted.
- Remove flat cells promptly. Amstrad warns that old cells left in the PPC can leak and cause damage.[2]
The real-time clock and its stored "last used" time run from the same battery pack, with no separate backup cell. With the batteries out, the time, the date and the last-used record are lost as soon as the external supply is disconnected.[3][4] Change the cells with the adaptor plugged in to keep the time.[4] If alkaline cells have leaked in the compartment, clean the contacts and holder as described in Battery Explosion, Capacitor or Corrosion Damage, which covers alkaline leakage. Battery Refurbishment lists the PPC's cells alongside other machines.
External power
[edit | edit source]- Use the Amstrad adaptor for your mains voltage: PPC640AC-B (240 V UK), PPC640AC-E (220 V Europe) or PPC640AC-A (120 V US). Its output is rated 1.9 A at 13 V.[3]
- The DC jack has its sleeve at ground and its centre pin positive. Amstrad rates the input at 12 V nominal, from 9.5 V to 17.5 V.[3] Check any substitute supply against those figures, and its polarity, before connecting it.
- The car adaptor (PPC640DC) is for 12 V negative-earth vehicles only.[3][2]
- An Amstrad PC-MD, PC-CD or PC-ECD monitor can power the PPC through the 14-way DIN socket.[2]
- Moving the power selector between EXT ON and EXT OFF resets the machine. Remove the discs before switching off, and wait at least five seconds before switching on again.[2]
When an expansion unit is fitted, Amstrad requires the PPC to be powered through the expansion connectors (+12 V 50 mA, +5 V 2.5 A, −5 V 50 mA, −12 V 50 mA, −20 V 30 mA, all ±5%), with the External Power pin tied to +12 V to disable the internal switching regulator and every other power source disconnected.[3]
Cleaning
[edit | edit source]Amstrad recommends an aerosol anti-static foam cleaner for the screen and the case, and no spirit-based cleaners.[2] The LCD is a complete exchange unit (LCD101, part 177245) for which Amstrad published no service data, so treat its surface gently.[1]
Opening the case
[edit | edit source]Unplug the adaptor and the telephone line and take out the battery tubes first. The machine itself runs from 12 V DC; the mains voltage is inside the external adaptor.[1] MCbx's procedure for the PPC512, which shares the PPC640's case and boards:[5]
- Leave the keyboard closed. Turn the machine over and open the battery compartment.
- Remove the six large screws.
- Lift the casing carefully, releasing the locks. There are wires everywhere. A large catch near the rear connectors has to be pried free with a screwdriver.
- Once that part is free, do not lift the half away. Open it like a book, because the speaker and battery leads run to it.
- The two main boards sit one inside the other. Remove the marked screws, squeeze the clips while lifting the board slightly, and unplug the transfer connector between the boards.
- Do not break the voltage regulator, the large three-pin device on a metal heatsink, off the board.
- If the LCD cable comes out, loosen its connector screws, refit it and tighten them again.
- On reassembly, push the wires between the halves of the transfer connector clear with a flat screwdriver.
The cabinet parts list on p. 16 of the service manual numbers each case part separately for the PPC512 and PPC640.[1]
Alignment
[edit | edit source]Amstrad's alignment instructions for the computer have two steps; the equipment list is a digital multimeter, an oscilloscope and the diagnostic disc or tool.[1]
| Step | Adjust | Measure at | Target | Notes |
|---|---|---|---|---|
| 1 | TC101 (200 pF trimmer) | Pin 21 of IC134 (real-time clock) | Read 0.00 on a timing meter (printed "Odometer") set to 0.2 sec/day | Only if the clock chip has been changed |
| 2 | VR501 (5 kΩ preset) | Junction of L501 and C514 | +5 V ±5% (4.75–5.25 V) | Run the PPC from the power adaptor |
Before turning VR501, check the C5xx electrolytics around the switching regulator, listed in the Amstrad PPC640 Capacitor Replacement Guide. The +5 V rail also has an overvoltage crowbar, SCR501 triggered through a 6.2 V zener (D529), so winding the rail too high can fire it.[1]
Floppy drives
[edit | edit source]The FD-5 drives are 720 KB 3.5-inch units. Amstrad's position was that the drive mechanism and its boards should not be serviced by engineers but exchanged complete, and the FD-5 section of the manual is marked "for information purposes only". It states that no preventive maintenance is needed under normal use, and that contaminated heads cause soft errors and can be cleaned with a non-abrasive head-cleaning disc.[1] Its alignment procedures need alignment discs (JU-01AA-DD and 817-363CE) and a drive exerciser.[1] See Floppy Drive Repair for general drive work.
The drives need double-density 720 KB discs. One owner reports using 1.44 MB discs with the density hole covered with tape, formatted to 720 KB, and finding them reliable at that capacity.[6]
Screen hinges
[edit | edit source]The LCD tilts on its own pair of hinges. Jan Schenk published a 3D-printable replacement for broken PPC512 and PPC640 screen hinges after both hinges on his PPC640 had snapped off. His notes:[7]
- Remove the screen and take it apart; he describes this as a pain but doable.
- If the hinge has broken cleanly at its base, slide the printed part in, filing a little if needed. If it broke higher up, remove the remaining plastic first.
- The part should be a tight fit without force. Check that the pins fit their holes in the case.
- Check that the screen housing still closes fully before final assembly.
Configuration switches
[edit | edit source]The display switches on the left-hand side are read only at reset, so a change has no effect until the PPC is reset.[2] The settings are tabulated on the Amstrad PPC640 page. An external monitor selected but not connected leaves the LCD blank with the CRT indicator lit; this is not a fault.[2]
Storage
[edit | edit source]Take the C cells out before putting the machine away, since cells left inside can leak.[2] Close the keyboard only with the power off: closing it with the power on sounds an alarm.[2]
Related pages
[edit | edit source]- Amstrad PPC640 · Amstrad PPC640 Troubleshooting Guide · Amstrad PPC640 Capacitor Replacement Guide
- Amstrad PPC 512 / PPC 640 Service Manual · Amstrad PPC 512 / PPC 640 User Instructions
- 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, PPC512S/512D, PPC640S/640D Personal Portable Computer Service Manual. Hosted as File:Amstrad PPC 512 PPC 640 Service Manual.pdf, described at Amstrad PPC 512 / PPC 640 Service Manual. Specification and notes to service engineers p. 2; FD-5 drive information pp. 3–11; alignment instructions p. 14; cabinet parts list p. 16; power supply schematic p. 26; electrical parts list pp. 29–31.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 Amstrad plc, The Amstrad Portable PPC 512/640 User Instructions (US edition, first edition 1988). Hosted as File:Amstrad PPC 512 PPC 640 User Instructions.pdf, described at Amstrad PPC 512 / PPC 640 User Instructions. Power sources (introduction); inserting the batteries p. 9; switching on p. 13; switching off p. 43; cleaning p. 50; switch settings pp. 317–318.
- ↑ 3.0 3.1 3.2 3.3 3.4 Amstrad Consumer Electronics plc, Amstrad PPC Technical Reference Manual (1987), transcribed by John Elliott at seasip.info. Retrieved 2026-10-02. Section 1.9 (real time clock), 1.18 (expansion power), 1.20 (power connectors), 1.21 (switch settings); section 2.6 (ROS messages).
- ↑ 4.0 4.1 Ewart Stronach, "Amstrad's PPC 512 and PPC 640 Portables", Your Computer (Australia), July 1988, pp. 62–64. Scan at archive.org. Retrieved 2026-10-02. The clock relies on the main batteries; the batteries can be changed with the DC adaptor in use without disturbing the clock.
- ↑ MCbx, "Amstrad PPC512", oldcomputer.info. Retrieved 2026-10-02. Disassembly, the two-board stack, the voltage regulator heatsink, the LCD cable and the memory upgrade.
- ↑ GXL750 and others, "My newest old computer, an Amstrad PPC", VOGONS forum, June 2012 to November 2019. Retrieved 2026-10-02. An owner's PPC640: contrast usable mainly in bright light, battery running time, 1.44 MB discs taped and formatted to 720 KB; a PPC512D owner missing the battery compartment cover.
- ↑ Jan Schenk (Coat), "Amstrad PPC512 / 640 screen hinge repair", Thingiverse thing 5255722 (2022), CC BY 4.0. Mirrored at archive.org. Retrieved 2026-10-02. Removing the screen, fitting the printed part to a clean break, filing to fit and checking the screen case still closes.