Amstrad PC1640 Capacitor Replacement Guide
The Amstrad PC1640 takes its power from whichever monitor it was sold with, the PC-MD, PC-CD or PC-ECD, so the capacitors that keep the computer running are on the monitor's main board.[1] Amstrad's service manual lists the electrolytics of all three monitors. The CPU board's parts list names only C801 (47 µF 16 V); the other electrolytics on the CPU board are not listed, and one of them, C124, is a known failure.[2] The procedure is the same as for the PC1512's monitors; see the Amstrad PC1512 Capacitor Replacement Guide.
Safety
editWarning: all three monitors run from the mains and contain a CRT; the 150 µF 400 V reservoirs hold a charge after unplugging.
- Discharge the tube and the reservoir capacitors before work; see CRT Discharge Procedure.
- After the work, Amstrad's tests are a 1.5 kV RMS flash test for 3 seconds, insulation above 4 MΩ and mains lead earth continuity under 0.5 Ω.[2]
CPU board: C124
editC124 sits on the +5 V feed through R181, the 5.6 Ω fusible resistor that powers IC110 (74LS125). On one PC1640 it failed short, burning out R181 and causing the BIOS's floppy controller error; owners give it as 100 µF.[3] Amstrad's PC2086 parts list, for a later board of the same family, also gives C124 as 100 µF (10 V or 16 V).[4] Read the value and voltage printed on the part in your machine before replacing it, and replace R181 at the same time if it has failed. The Amstrad PC1640 Troubleshooting Guide has the full fault report.
PC-MD electrolytic capacitors
edit| Ref | Value | Voltage | Amstrad part no. |
|---|---|---|---|
| C4118 (as printed) | 4.7 µF | 25 V | 175139 |
| C426 | 22 µF | 160 V | 1400243 |
| C505 | 150 µF | 400 V | 171603 |
| C804 | 330 µF | 63 V | 175140 |
| C522 | 470 µF | 16 V | 1400248 |
| C517, C521, C530 | 1000 µF | 16 V | 1400158 |
| C402 | 2200 µF (first digit faint in the scan) | 16 V | 175141 |
| C528, C529 | 3300 µF | 16 V | 171607 |
| C525 | 3300 µF | 35 V | 171608 |
The list also has two parts under "Almi electrolytic capacitors", C549 (EFE222, 175126) and C550 (CFE222, 175127), with type codes in place of values.[2] The PC-MD's supply is driven by an STK7358 (IC501).[2]
PC-CD electrolytic capacitors
edit| Ref | Value | Voltage | Amstrad part no. |
|---|---|---|---|
| C436 | 22 µF | 250 V | 171649 |
| C506, C601 | 150 µF | 400 V | 171650 |
| C515 | 220 µF | 160 V | 171651 |
| C516 | 470 µF | 35 V | 171653 |
| C623 | 1000 µF | 16 V | 1422158 |
| C437 | 1000 µF | 35 V | 1422159 |
| C408 | 2200 µF | 35 V | 1422160 |
| C621, C622 | 3300 µF | 16 V | 171654 |
| C618 | 3300 µF | 35 V | 171655 |
These values match the same positions on the PC1512's PC-CM; the PC-CM list adds C440, C509 and C613.[2][5]
PC-ECD electrolytic capacitors
edit| Ref | Value | Voltage | Amstrad part no. |
|---|---|---|---|
| C465 | 2.2 µF | 50 V | 175144 |
| C429 | 4.7 µF | 100 V | 175116 |
| C440 | 22 µF | 250 V | 171649 |
| C506, C601 | 150 µF | 400 V | 171450 |
| C515 | 220 µF | 160 V | 171651 |
| C613 | 330 µF | 25 V | 171652 |
| C516 | 470 µF | 35 V | 171653 |
| C457, C623 | 1000 µF | 16 V | 1422158 |
| C441 | 1000 µF | 35 V | 1422159 |
| C427 | 2000 µF (as printed) | 35 V | 1422160 |
| C621, C622 | 3300 µF | 16 V | 171654 |
| C618 | 3300 µF | 35 V | 171655 |
C427 is printed as 2000 µF but carries part number 1422160, the number used for the 2200 µF 35 V C408 in the PC-CD list; check the part fitted. The 150 µF 400 V reservoirs carry part number 171450 here and 171650 in the PC-CD list.[2] C505 on the PC-ECD is a 2200 pF 125 V ceramic capacitor, not an electrolytic.[2]
The PC-ECD's TTL decoder board is soldered to the main board. An owner who recapped it had to desolder the board to reach its capacitors, and lifted a track at C118 in the process; the schematic let him repair it.[6] In that monitor the black screen turned out to be a failed 5 V regulator, IC503, not the capacitors, so measure the supply rails before recapping.[6]
After the recap
editSet the rails to Amstrad's targets: +5 V 5.10 V ±0.02 V, +12 V 12.15 V ±0.02 V, −5 V and −12 V to 5 V and 12.0 V ±0.05 V in magnitude, and the +12 V protection to trip at 4.5 A. The presets are VR505, VR504, VR501, VR502 and VR507 on the PC-MD, and VR604, VR603, VR601, VR602 and VR606 on the PC-CD and PC-ECD.[2] Check the result at the 14-way DIN plug, then run the picture adjustments and the safety tests.
Related pages
editReferences
edit- ↑ Amstrad, PC1640 Technical Reference Manual, section 1.21 "Power Connector", transcribed by John Elliott: seasip.info. Retrieved 2026-10-02. The supply in the monitor and the 14-way DIN pinout.
- ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Amstrad plc, PC1640 Personal Computer, PC-MD Monochrome Display, PC-CD Colour Display, PC-ECD Enhanced Colour Display Service Manual. Hosted as File:Amstrad PC1640 Service Manual.pdf, described at Amstrad PC1640 Service Manual. Safety tests p. 2; PC1640 electrical parts list p. 26; PC-MD electrical parts list p. 35; PC-CD electrical parts list pp. 40–41; PC-ECD electrical parts list p. 46; alignment instructions pp. 40, 41 and 47.
- ↑ jarcher1701, modem7, austfox and others, "Amstrad PC1640 – Faulty Floppy Disk Controller or Disk Drive", Vintage Computer Federation Forums, October–December 2023. Retrieved 2026-10-02. Community repair: C124 (100 µF) failed short, R181 burnt out, IC110 without power, and the floppy controller error.
- ↑ Amstrad plc, PC2086 S/D/30 Personal Computer Service Manual. Hosted as File:Amstrad PC 2086 Service Manual.pdf, described at Amstrad PC 2086 Service Manual. Electrical parts list p. 4.
- ↑ Amstrad plc, PC1512 Personal Computer, PC-MM Monochrome Monitor, PC-CM Colour Monitor Service Manual. Hosted as File:Amstrad PC1512 Service Manual.pdf, described at Amstrad PC1512 Service Manual. PC-CM electrical parts list p. 20.
- ↑ 6.0 6.1 VintageVic, "Amstrad PC ECD display 'Black screen' – advices welcome", Vintage Computer Federation Forums, 18–19 June 2026. Retrieved 2026-10-02. Community repair: recapping the PC-ECD TTL decoder board and main board, a lifted track at C118, and the failed IC503 regulator that was the actual fault.