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Amstrad GX4000

Amstrad's console (September 1990, Europe only): really a CPC Plus without a keyboard, in a console shell with games on cartridge. A late release (8-bit in the 16-bit era), a thin library and pricey carts made it a commercial failure (< 15,000 units), discontinued as early as 1991.

Amstrad GX4000

Amstrad GX4000 — photo by Evan-Amos, domaine public (Wikimedia Commons).

Identification

Field Value
Manufacturer Amstrad
Released September 1990 — UK, France, Spain, Italy
Price £99.99 / Fr 990 (games ~£25 / cartridge)
Hardware base CPC Plus range (464 Plus / 6128 Plus)
Media ROM cartridge (up to 512 KiB)
Region / video PAL 50 Hz — RGB SCART + composite + RF
Bundled Burnin' Rubber, a power pack, 2 controllers

Architecture (detail)

Block Chip Clock Role
CPU Zilog Z80A 4 MHz 8-bit CPU, identical to the CPC
Graphics "Plus" ASIC 16 hardware sprites 16×16 (×2/×4 magnify), hardware scrolling, 4096-colour palette (32 on-screen)
Sound General Instrument AY-3-8912 (3-channel PSG, stereo) + DMA sound (lists handled by the ASIC)
Memory 64 KiB RAM of which 16 KiB is VRAM

Video modes (inherited from the CPC): 160×200 (16 c.), 320×200 (4 c.), 640×200 (2 c.).

The GX4000 is hardware-identical to a CPC Plus: same cartridges as the CPC 464 Plus / 6128 Plus (a CPC Plus reads GX4000 carts and vice-versa). What the Plus range added over the original CPC is the sprites, hardware scroll, 4096 palette and DMA sound — but with no keyboard and no tape/disk drive, the machine can load only from cartridge, which throttled the software supply.

Why it failed (preservation context)

  • A library of only ~27 games, often unambitious CPC ports.
  • £25 cartridges against CPC cassettes at £3.99 → buyers balked.
  • An 8-bit machine launched in 1990, against 16-bit Mega Drive / Super Famicom.
  • Slow manufacturing, patchy distribution, weak marketing.

Common faults

Symptom Likely cause Lead
Cartridge not read / crash oxidised cart contacts Clean the connector (isopropyl alcohol)
No power external power pack dead (original brick) Test/replace the PSU (check voltage/polarity)
No picture RGB SCART cable/output, or ASIC Check the SCART cable and the TV input
Degraded picture/sound ageing capacitors Targeted recap of the affected stage

Procedure — a dead console, step by step ✅

What this adds

Ordered for a console, not for an arcade board: what kills these is almost never the CPU. It is, in real order, the power supply, the capacitors, the drive or the cartridge slot, and only then the logic. → PCB diagnosis

1. The power supply. Two cases, depending on the machine. External brick: ⚠️ read the marking on the machine, next to the socket, and check the adapter against it — voltage and polarity. A centre-negative machine fed centre-positive loses its fuse, sometimes its regulator; do not trust a third-party label or a generic tip. Internal supply (the machine plugs straight into the wall): mains is inside the shell. Unplug, wait, and confirm the large capacitors are discharged before touching the board. Either way, measure under load: a failing supply holds its voltage until it is asked for current.

2. The fuse. Many of these machines have one right behind the socket — it is the part designed to die. Test it in continuity, out of circuit. A fuse that blows again is a short, not a fuse problem.

3. Capacitors. On most machines of this age this is the default suspect rather than a last resort — leaking SMD electrolytics eat the tracks underneath before they give any other sign. ⚠️ Not all of them are like that: some carry very few and are not recapped on principle. Read what this page says about it before reaching for the iron. → Recap

4. The cartridge connector. Cartridge contacts with isopropyl alcohol, never an abrasive eraser: it takes the gold plating off and the problem comes back worse. On the machine side, inspect the slot pins — splayed, bent or oxidised — and check continuity between slot and board.

5. Video output. Isolate the machine from the display: another cable, another TV, another input. A sizeable share of "dead consoles" are a dead cable, or a display that will not lock onto what this machine outputs — see the video section of this page for what that is.

6. Still nothing. Now, and only now, the logic: rails on the board, reset, clock, bus. → PCB diagnosis

Mods & repair — what to buy, how

  • Factory RGB SCART output 🟢: clean RGB with no mod (a big edge over the era's consoles) → an Amstrad SCART cable then OSSC/RetroTINK/RGB2HDMI.
  • C4CPC flashcart 🟢: an SD cart loading Plus / GX4000 games in the cartridge port — plug-and-play, ideal for preservation.
  • Power: the GX4000 is fussy about its PSU → check/replace with a stable supply (a weak supply = crashes).
  • Controller: stock pads get flaky → refresh the contacts or use an adapter (the port is an Atari/joystick type — connect with care).
  • Cartridge contact cleaning + recap if the video/sound stage is tired.
  • ⚠️ Do not host ROMs/cartridges — we describe the method, not the protected content.

Photos / assets

(To add: GX4000 console, controller, cartridge, motherboard.)

Advanced repair — cross-cutting methods

PCB fault-finding · Recap · Traces & vias.

Archived technical documentation ✅

Manufacturer documentation archived locally: schematics, block diagrams, expected voltages, parts lists. The reference when a symptom matches no known fault.

  • GX4000 — PDF

Status

Manufacturer documents kept for preservation (machines out of production for decades), with no explicit licence — the same position as for the cabinet manuals already archived here.

GX4000 schematics ✅

ASIC, CPU, memory/video, power and RGB — plus the French variant.

Provenance

Schematics of undocumented origin in the collection they came from: no author and no licence is stated there.

GX4000 schematics — edited asic schematic
GX4000 schematics — edited french schematic
GX4000 schematics — edited rgb power schematic
GX4000 schematics — edited vid mem cpu schematic
GX4000 schematics — asic schematic
GX4000 schematics — cpu schematic
GX4000 schematics — memory video schematic
GX4000 schematics — power schematic
GX4000 schematics — rgb schematic

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

Reading is open to everyone; posting requires signing in with Discord. Reports from the wiki's declared reviewers are handled first; anyone else's are read too, but go through a human before anything is changed.