RetroTechCollection

Amstrad GX4000 Capacitor Replacement Guide

Amstrad's electrical parts list for the Amstrad GX4000 gives 23 aluminium electrolytic capacitors in six values on the main board. The table below is taken from that list, on printed page 36 of the Plus range service manual, with one misprinted reference corrected from the schematic.[1]

GX4000 main PCB MC0123A, top view, with circuit references (Amstrad service manual p. 24)

Electrolytic capacitors

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GX4000 electrolytic capacitors (parts list, p. 36)
Value Circuit reference Amstrad part no.
470 µF / 16 V C182 (printed "R182") 157630
470 µF / 10 V C102, C103, C104, C121 270983
100 µF / 10 V C30, C35, C120 240463
22 µF / 25 V C100, C101, C107, C109, C113, C114, C115, C116, C118, C128 250409
10 µF / 50 V C26, C32, C34 240462
1 µF / 50 V C201, C202 157563

The parts list prints the 470 µF 16 V part against "R182". The power regulator schematic shows it as C182, 16 V 470 µF, between the diode D181 and the resistor R181 on the 11 V adaptor input.[1]

The RGB converter schematic (p. 30) marks C128 as 16 V 100 µF, where the parts list gives 22 µF 25 V. Read the part fitted to your board before ordering.[1]

Where they are

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The RGB converter schematic places several of these parts in the television outputs. C102, C103 and C104 (470 µF) are in series with the red, green and blue outputs of the CXA1145P encoder (IC101) to the Peritel socket, and C121 (470 µF) is in the composite output to the same socket. C113 to C116 (22 µF) are on the red, green, blue and sound lines at the encoder.[1] A failed coupling capacitor in the Peritel outputs shows as one weak or missing colour on a television; the monitor DIN socket does not use them. See Capacitor Failure Symptoms.

 
An MC0123C board. C102, C103 and C104 are beside the sound switch SW101 next to the RF modulator, C121 is below the Peritel socket, and C182 is beside the DC sockets at top right.

The board in the photograph is revision MC0123C (2700-017P-4); the manual draws MC0123A (2700-017P-3).[1][2]

Console5's list

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Console5's Tech Wiki has a community list of 18 electrolytics for the GX4000, with a capacitor map credited to "mezaar".[3] Its values agree with Amstrad's for every reference both lists share. It differs in these places:

  • It includes C40 (1 µF 50 V) and C185 (22 µF 25 V), which are not in Amstrad's electrolytic list. On Amstrad's RGB converter schematic C185 is a 0.01 µF part.[3][1]
  • It omits C100, C107, C109, C116, C118, C120 and C201, which are in Amstrad's list.[3][1]

On the MC0123C board in the photograph, C185 is silkscreened with a polarity mark but no part is fitted, and C109 is fitted.[2] Count the electrolytics on your own board against both lists before ordering.

Other capacitors

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The parts list also gives ceramic capacitors: 47 pF (C119), 82 pF 50 V (C140 to C142), 100 pF 50 V (C27, C31, C106, C131), 330 pF 50 V (C24, C25, C135 to C137), 0.01 µF (C105, C124, C134, C138, C139) and 0.1 µF 12 V decoupling (C1, C2, C8, C10, C11, C14, C15, C17 to C19, C33, C110, C122, C133, C181, C183, C184, C401).[1] These are not part of a routine recap.

Replacement procedure

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  1. Disconnect the adaptor, the monitor leads and the paddles, and remove the cartridge. Open the case as described in the Amstrad GX4000 Maintenance Guide.
  2. Photograph the board and note the polarity of every electrolytic before removing it.
  3. Remove one capacitor at a time with a desoldering iron or braid. Do not pull a lead against unmelted solder; the pads lift easily.
  4. Clean the pads and check them for corrosion from leaked electrolyte. See Battery Explosion, Capacitor or Corrosion Damage for cleaning.
  5. Fit a part with the same capacitance, the same or a higher voltage rating, and a body that fits the space. Match the polarity to the board marking.
  6. Reassemble and test with a cartridge on both a monitor and a television if you have them.

The Amstrad 464 Plus Capacitor Replacement Guide covers the same procedure for the Plus computers.

After the recap

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  • With the adaptor connected, measure 5 V after the power switch and at the output of IC181 (L7805), and the +10 V line after R181.[1]
  • On the UK board, check the +5 V MOD output of IC17 and the RF picture on channel 36; adjust the modulator coil if needed.[1]
  • Check all three colours on a Peritel television and on an Amstrad monitor.
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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 Amstrad plc, 464 PLUS Home Computer / 6128 PLUS Home Computer / GX4000 Games Console / MM 12 Monochrome Monitor / CM 14 Colour Monitor Service Manual, GX4000 section. Hosted as File:Amstrad GX4000 Service Manual.pdf, described at Amstrad GX4000 Service Manual. Main PCB top view p. 24; power regulator schematic p. 29; RGB converter schematic p. 30; electrical parts list p. 36.
  2. ↑ 2.0 2.1 Evan-Amos, "Amstrad-GX4000-Motherboard-Flat-Top.jpg", Wikimedia Commons, 2017 (public domain). Retrieved 2026-10-02. Board markings MC0123C and 2700-017P-4, the positions of C102, C103, C104, C121 and C182, the fitted C109 and the empty C185 position.
  3. ↑ 3.0 3.1 3.2 Console5 Tech Wiki, "Amstrad GX4000", cap list. Retrieved 2026-10-02. Secondary source: a community list, not Amstrad's.


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