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Amstrad NC150 Capacitor Replacement Guide

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Amstrad NC100 main board, power section (Adam Wilson)
Power end of an NC100 main board (4500-001P-1), photographed by Adam Wilson. The NC users' site gives the NC150 the same hardware as the NC100.

The Amstrad NC150 was sold only in France and Italy, from April 1993, in the same flat case as the Amstrad NC100. Tim Surtell's NC users' site describes it as having the same hardware as the NC100, with 128 KB of RAM in place of 64 KB and provision for an external floppy drive as the only hardware differences.[1] No teardown of an NC150 has been published, and no Amstrad parts list or circuit diagram for either machine is available, so the NC150's board number and capacitor values are unconfirmed. The checks below start from what is known of the NC100 board.

Before you start

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The NC150 keeps everything in battery-backed RAM, with four AA cells, a mains adaptor input and a lithium backup cell. Böhling's power supply diagram, titled "NC100/150", shows the adaptor input passing through fuse F301 to a DC/DC converter that produces +6 V, +5 V, a lithium-backed 5 V supply for the RAM and clock, and −15 V for the display.[2] Copy the documents to a memory card before opening the case; if every power source is removed at once the memory is lost. The Amstrad NC150 Maintenance Guide covers the cells and backup.

Identify the board

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Open the case as for the NC100 (see the NC100 procedure) and read the number printed on the main board.

  • The NC100 board is marked "AMSTRAD plc 4500-001P-1".[2][3]
  • The NC100 board was laid out with link options for larger firmware EPROMs, including the 512 KB 27C4001, and for different SRAM chips.[2] The NC150 has 512 KB of ROM and 128 KB of RAM.[4] Look at the memory and EPROM positions to see which options your board uses.

If the board carries the 4500-001P-1 number, the electrolytic positions and the values read from an NC100 board are in the NC100 guide: C301, C305 and C306 at the adaptor end, four small capacitors beside the RS-232 driver, and C343.[3] If it carries a different number, record every part as below.

Recording your board

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  1. Photograph both sides of the board with its number in shot.
  2. For each electrolytic, note the designator, capacitance, voltage, can size and polarity.
  3. Compare the list with the NC100's, position by position, and note every difference.
  4. Keep the record with the machine.

Procedure

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  1. Back up the documents, then remove the four AA cells.
  2. Remove the screws from the base, including the one under the battery cover and the one that holds the EPROM cover, and lift the upper case. Unplug the display cable and speaker lead.[2]
  3. Release the board from the case, following the NC100 steps, which apply to the shared case.
  4. Replace the electrolytics one at a time with parts of the same value and the same or a higher voltage, observing polarity and keeping within the height the case allows.
  5. Check fuse F301 for continuity while the board is out.[2]
  6. Reassemble and test on cells, then on the adaptor.

After the recap

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Switch on and check that the stored documents and the clock are intact, and that the serial port works if the capacitors beside the RS-232 driver were changed. If the lithium cell needs replacing, see the Amstrad NC150 Maintenance Guide.

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References

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  1. ↑ Tim Surtell, Tim's Amstrad NC Users' Site, "Introduction" and "Specifications of the NC Computers". Retrieved 2026-10-19. The NC150 launched in April 1993 with "the same hardware as the NC100" and the NC200's software, its only hardware differences being 128 KB of RAM and the option of an external floppy drive; French and Italian versions only; four AA cells and a 6 V adaptor.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 Hans-Jürgen Böhling, A Surgical Guide To The Amstrad Notepad Computer. Community document, hosted as File:Amstrad NC100 Surgical Guide.pdf, described at Amstrad NC100 Surgical Guide. The "NC100/NC150" block diagram and "NC100/150" power supply block diagram; the NC100 board 4500-001P-1 and its IC table; the zero-ohm links beside IC303 for larger EPROMs, including the 512 KB 27C4001; the SRAM links for 43256 parts with the unfitted IC310; opening the case. No component values.
  3. ↑ 3.0 3.1 Adam Wilson, "1992 Amstrad NC100 Notepad Computer Repair", Adam's Vintage Computer Restorations, 12 June 2023. Retrieved 2026-10-19. Photographs of an NC100 main board marked 4500-001P-1 and NA 999-32141 before and after replacement of its three larger electrolytics, C301, C305 and C306.
  4. ↑ Robin Nixon and Chris Nixon, The Amstrad Notepad Advanced User Guide (Sigma Press, 1993), p. 247, "New Notepad models". Scan at archive.org. Retrieved 2026-10-19. The NC150's 512K ROM and 128K RAM against the NC100's 256K and 64K.


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