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[[File:Amstrad CPC 464 with CTM 640.jpg|thumb|right|300px|CPC 464 with the CTM640 colour monitor. The monitor contains the computer's only power supply — and the only mains voltage in the system.]]
[[File:Amstrad CPC 464 with CTM 640.jpg|thumb|right|300px|CPC 464 with the CTM640 colour monitor, which holds the system's only power supply]]
Preventive maintenance for the '''[[Amstrad CPC 464]]''' (1984), covering the main PCB, the cassette sub-PCB and deck, the keyboard, the monitor that supplies the machine's power, and the connectors. Fault diagnosis is in the [[Amstrad CPC 464 Troubleshooting Guide]]; component values are in the [[Amstrad CPC 464 Capacitor Replacement Guide]].
Routine maintenance on the [[Amstrad CPC 464]] centres on the cassette deck and its board, the keyboard, the connectors and the monitor that powers the machine. Fault diagnosis is in the [[Amstrad CPC 464 Troubleshooting Guide]] and component values are in the [[Amstrad CPC 464 Capacitor Replacement Guide]]. Part numbers and alignment figures are from Amstrad's service manual.<ref name="sm464">Amstrad Consumer Electronics plc, ''CPC464 Micro Computer / CTM640 Colour Monitor / GT64 Green Monitor Service Manual''. Described at [[Amstrad CPC 464 Service Manual]]. Technical specification and cabinet parts list p. 2; cassette mechanism parts list and alignment instructions p. 6; cassette PCB p. 7; basic hardware analysis p. 9; cassette and software analysis p. 10; electrical parts list p. 17.</ref>


Part numbers, circuit references and alignment figures on this page are Amstrad's own, from the [[Amstrad CPC 464 Service Manual]] hosted on this wiki.<ref name="sm464">Amstrad Consumer Electronics plc, ''CPC464 Micro Computer / CTM640 Colour Monitor / GT64 Green Monitor Service Manual''. Hosted at [[Amstrad CPC 464 Service Manual]]. Source for the technical specification (page 2), the CPC464 Cabinet Parts List (page 2), the Cassette Mechanism Parts List and Cassette Deck Alignment Instructions (page 6), the Cassette PCB layout (page 7), the Basic Hardware Analysis flow chart (page 9), the Cassette &amp; Software Analysis chart (page 10) and the CPC464 Electrical Parts List (page 17).</ref>
== Power and safety ==


== The monitor is the power supply ==
The CPC 464 has no mains connection and no power supply of its own. It takes 5&nbsp;V DC through a socket on the back, which Amstrad's specification says is "supplied exclusively from screen", the CTM640 colour or GT64 green monitor.<ref name="sm464" />


'''The CPC 464 has no mains connection and no internal power supply.''' The machine takes 5 V DC through a DC socket on the back, and Amstrad's own specification states that this is "supplied exclusively from screen system" — the CTM640 colour monitor or the GT64 green monitor.<ref name="sm464" /> Mains enters the ''monitor'', not the computer.
* The keyboard unit carries no mains voltage. Work on it with the DC lead unplugged and anti-static precautions.
* The monitors contain the mains supply and a CRT, and hold a dangerous charge after switch-off. Read [[CRT Discharge Procedure]] before opening one.
* Amstrad's fault chart for a dead machine starts at the monitor: mains fuse, then the DC output and lead, then the computer.<ref name="sm464" />


That changes how you approach a dead machine, and it changes the hazards:
Amstrad's safety test for the monitors is a 4&nbsp;kV flash test between the mains lead (live and neutral joined) and all accessible metal, and an insulation test between the same points requiring at least 4&nbsp;MΩ.<ref name="sm464" />
 
* '''The computer itself is safe to open.''' There is no mains voltage anywhere inside the keyboard unit. You can work on the main PCB, the cassette PCB and the keyboard with the DC lead disconnected and nothing worse than static to worry about.
* '''The monitor is not.''' The CTM640 and GT64 contain a CRT with a lethal anode charge and mains-derived bulk capacitors that hold charge after switch-off. Read [[CRT Discharge Procedure]] before opening either.
* '''A "dead CPC" is very often a dead monitor.''' Amstrad's own fault-finding chart sends you to the monitor's 5 V supply and the DC cord before anything on the computer board.<ref name="sm464" />
 
Amstrad's safety-test specification for the monitors, for reference: a flash test at '''4 kV''' between the mains lead (live and neutral joined) and all accessible exterior metal, and an insulation-resistance test on the same points showing at least '''4 MΩ'''.<ref name="sm464" />


== Identifying your board ==
== Identifying your board ==


The CPC 464 main PCB went through four broad versions, identified by the silkscreened part number. The chip set, the board size and the keyboard connector all differ.<ref name="cpcwikimb">[https://www.cpcwiki.eu/index.php/Mainboard_Versions "Mainboard Versions"], CPCWiki. Community catalogue of silkscreen markings, board dimensions, copyright dates and per-version changes for the CPC 464, 664 and 6128 main boards. Secondary source, compiled from observed boards.</ref>
CPCWiki's catalogue of photographed boards identifies four CPC 464 main board versions by their silkscreened part number.<ref name="cpcwikimb">CPCWiki, [https://www.cpcwiki.eu/index.php/Mainboard_Versions "Mainboard Versions"]. Retrieved 2026-10-01. Community catalogue of board markings, sizes and per-version changes, compiled from photographed boards.</ref>


{| class="wikitable styled-table" style="width:100%; text-align:left;"
{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Amstrad CPC 464 main PCB versions'''<ref name="cpcwikimb" />
|+'''CPC 464 main board versions'''
! Version !! Silkscreen !! Size !! Notes
! Version !! Silkscreen !! Size !! Notes
|-
|-
| '''v1''' (©1983) || Z70100 (no MC code), 270100 MC0001A, or Z70100 MC0001A || 405 × 155 mm || Gate Array with a cooling plate; VCC2 fed through R138/R139
| 1 (©1983) || Z70100; 270100 MC0001A; Z70100 MC0001A || 405 × 155&nbsp;mm || Gate array under a cooling plate, its VCC2 fed through R138 and R139; keyboard wired to the board on the first boards
|-
|-
| '''v2''' (©1984) || Z70200 with MC0001A, MC0002A/B/C/D, MC0003A, MC0008B/C/D || 405 × 152 mm || Separate solder pads for both the old and the new Gate Array; 6128-style 2 × 10-pin dual-foil keyboard connector
| 2 (©1984) || Z70200 with MC0001A, MC0002A–D, MC0003A, MC0008B–D || 405 × 152&nbsp;mm || Pads for both the old and new gate array; connector for the 6128-style 2 × 10-pin membrane keyboard
|-
|-
| '''v3''' || Z70374 MC0044A, Z70374 MC0044B, Z70375 MC0044D, Z70378 MC0046A || 240 × 150 / 238 × 145 mm || Same parts packed tighter; joystick and stereo sockets moved to the left side
| 3 || Z70374 MC0044A/B, Z70375 MC0044D, Z70378 MC0046A || 240 × 150 or 238 × 145&nbsp;mm || Same parts packed more tightly; joystick and stereo sockets on the left
|-
|-
| '''v4''' "cost-down" (©1988) || '''Z80329 MC0099A''' || 237 × 108 mm || 100-pin SMD ASIC (part 40226) combining the Gate Array, CRTC and some FDC, DRAM and reset logic
| 4, cost-down (©1988) || Z80329 MC0099A || 237 × 108&nbsp;mm || 100-pin surface-mount ASIC (Amstrad 40226) combining the gate array, CRTC and some floppy, DRAM and reset logic<ref name="cpcparts">CPCWiki, [https://www.cpcwiki.eu/index.php/Amstrad_part_numbers "Amstrad part numbers"]. Retrieved 2026-10-01. Community list of Amstrad custom-chip and PCB numbers.</ref>
|}
|}


On the original board Amstrad's own parts list gives the Gate Array as '''IC116, marked 20RA043''', Amstrad part number 40007.<ref name="sm464" />
On the original board Amstrad's parts list gives the gate array as IC116, 20RA043, part 40007.<ref name="sm464" /> CPCWiki lists 40007 and 40008 as the heat-sinked gate arrays and 40010 as the later one without a heat sink, with different pinouts.<ref name="cpcparts" />


== Opening the unit ==
== Opening the unit ==
Tools: a Philips screwdriver and an anti-static strap.


# Switch off and unplug the DC lead from the monitor.
# Switch off and unplug the DC lead from the monitor.
# Disconnect any joystick, printer or expansion-port peripheral.
# Disconnect any joystick, printer or expansion-port device.
# Lay the keyboard face-down on a soft cloth and remove the underside screws. The count varies by board version; some are hidden under the model-name label.
# Lay the keyboard unit face down on a soft cloth and remove the screws from the underside.
# Lift the lower half of the case.
# Lift the case apart, minding the keyboard cable, and photograph the cable routing before you unplug anything.
# Disconnect the keyboard cable. On v1 boards this is discrete wiring — '''photograph the colour order before you unplug anything'''. From v2 onward it is a 2 × 10-pin dual-foil connector.<ref name="cpcwikimb" />
# Disconnect the keyboard cable and the cassette board's 8-way connector, CD001.
# Disconnect the cassette PCB at '''CD001''', the 8-way connector on the cassette board. Amstrad labels the conductors on the PCB layout: 1 INPUT, 2 PLAY ON (yellow), 3 SOUND IN (white), 4 DATA OUT (green), 5 DATA IN (blue), 6 GND (black), 7 +B (white), 8 +B (red).<ref name="sm464" />


'''Almost all the analogue electronics are on the cassette PCB, not the main board.''' It carries IC301 (LA4140 audio power amplifier), IC302 (LA6324 quad op-amp for the cassette read chain), VR301 (the 20 kΩ volume control), RY301 (the tape motor relay), SP301 (the speaker), L301, D301, D302 (the red power LED, SLP-145B) and the whole 300-series resistor and capacitor population.<ref name="sm464" /> If you are chasing an audio or tape fault, that is the board you want.
Amstrad's cassette PCB drawing labels the CD001 conductors: 1 +B (red), 2 GND (black), 3 +B (white), 4 DATA IN (blue), 5 DATA OUT (green), 6 SOUND IN (white), 7 PLAY ON (yellow), 8 INPUT.<ref name="sm464" />


== Regular cleaning ==
The cassette PCB (PCB301) carries the audio and tape electronics: IC301 (LA4140), IC302 (LA6324 quad op-amp), the tape motor relay RY301, the 300-series resistors and twelve of the fourteen electrolytic capacitors. The volume control VR301 is on the small board PCB302 beside it.<ref name="sm464" /> Audio and tape faults are usually on these boards.


* Soft brush and low-pressure air for the main PCB, the keyboard mat and the cassette mechanism. Hold the cassette flywheel by hand if you use air near it.
== Cleaning ==
* Clean the R/P head (Amstrad part '''170201'''), capstan and pinch roller with IPA on a '''foam''' swab. Cotton fibres left in the head gap are a known cause of intermittent reads.
* Clean the connectors — the 6-pin DIN video socket J101, the 9-pin D joystick socket J102, the 3.5 mm socket J103 and the DC socket J104 — with contact cleaner sparingly on a foam swab.<ref name="sm464" />
* Clean the keyboard rubber contact mats (Amstrad parts '''170008''' key board mat, '''170009''' digit mat, '''170010''' spacer) by rolling them gently in a damp lint-free cloth. Do not soak the silicone in solvents.


== Keyboard maintenance ==
* Brush and low-pressure air for the main board, keyboard mat and cassette mechanism.
* Clean the record/play head (part 170201), capstan and pinch roller with isopropyl alcohol on a foam swab.
* Clean the sockets J101 to J104 with a little contact cleaner on a swab.<ref name="sm464" />
* Clean the rubber contact mats (parts 170008 key mat, 170009 digit mat, 170010 spacer) with a damp lint-free cloth.<ref name="sm464" />


The CPC 464 keyboard is a '''74-key''' assembly in QWERTY layout with a numeric cluster, cursor and copy cursor, large enter, shift, caps lock, tab, escape, delete, clear and control.<ref name="sm464" /> It is built up from keytops, silicone rubber contact mats (170008/170009/170010) and a flexible contact PCB in two halves (Amstrad parts '''170028''' and '''170029''').<ref name="sm464" />
== Keyboard ==


Common faults:
The keyboard has 74 keys: QWERTY with a numeric cluster, cursor and copy cursor, large enter, shift, caps lock, tab, escape, delete, clear and control.<ref name="sm464" /> It is built from keytops, the rubber contact mats and a contact PCB in two halves (parts 170028 and 170029).<ref name="sm464" /> Amstrad's fault chart for keys that do not work sends you to inspect the keyboard PCB for cracks, liquid spillage and distorted mounting, and then to check the connector lead and its termination.<ref name="sm464" />


* '''A whole row dead''' — a broken membrane trace, or a fault in the cable between the contact PCB and the main board. Reseat the cable first, then check continuity along the row's track.
== Cassette deck ==
* '''A single key dead''' — dirty contact. Clean the carbon pill on the silicone dome and its matching pad on the membrane with IPA on a swab. '''Do not abrade the pill''' — it is a conductive coating, not metal, and rubbing it off is permanent.
* '''A single key permanently active''' — a short on the membrane, usually an old liquid spill that crystallised between adjacent traces. Clean the area with IPA. Scoring the membrane between the pads to isolate the trace is a last resort.
* '''Soft keys, no click''' — a collapsed silicone dome. Replace from a donor mat.


Amstrad's own fault chart for "do all keys operate?" sends you to inspect the keyboard PCB for '''cracks, liquid spillage and distorted mounting''', then to check the connector lead and its termination.<ref name="sm464" />
{| class="wikitable styled-table" style="width:70%; text-align:left;"
 
|+'''CPC464 cassette mechanism, service parts (p. 6)'''
== Cassette deck maintenance ==
 
The deck is a single-motor mechanism. Amstrad's parts list gives every wear item a number:<ref name="sm464" />
 
{| class="wikitable styled-table" style="width:85%; text-align:left;"
|+'''CPC464 cassette mechanism — service-relevant parts'''<ref name="sm464" />
! Part !! Amstrad part no.
! Part !! Amstrad part no.
|-
|-
| '''Main Belt''' || 170204
| Main belt || 170204
|-
|-
| R/P Head || 170201
| R/P head || 170201
|-
|-
| Erase Head || 170202
| Erase head || 170202
|-
|-
| Pinch Roller Assembly || 809162
| Pinch roller assembly || 809162
|-
|-
| Spring, Pinch Roller || 809161
| Spring, pinch roller || 809161
|-
|-
| Flywheel || 809156
| Flywheel || 809156
|-
|-
| Idler Assembly || 809155
| Idler assembly || 809155
|-
|-
| Idler Gear || 809173
| Idler gear || 809173
|-
|-
| Motor || 170208
| Motor || 170208
|-
|-
| Motor Pulley || 170211
| Motor pulley || 170211
|-
|-
| Counter Belt || 170014
| Counter belt (cabinet list) || 170014
|-
|-
| Cassette Mechanism (complete) || 170012
| Cassette mechanism, complete (cabinet list) || 170012
|}
|}


* '''Main belt (170204)''' — the usual failure. Thirty-plus-year-old originals are almost universally either liquefied into a sticky black residue on the pulleys or stretched beyond useful tension. Symptom: the motor runs but the capstan does not turn, and tapes will not load. Amstrad publishes no replacement dimensions, only the part number, so '''measure your own pulleys''' before ordering a generic belt. Clean off the old residue with IPA first — new belts will not grip through it.
When the motor runs but the capstan does not turn, check the main belt (170204). Amstrad gives only the part number, not the belt's dimensions, so measure the pulleys before ordering a generic belt, and clean any residue of the old belt off the pulleys first.
* '''Pinch roller (809162)''' — hardens and develops flats with age. Symptom: tape speed drifts under load, or the tape edge curls because the roller no longer presses evenly.
* '''Head and capstan cleaning''' — IPA on a foam swab, annually or every fifty tapes. Do not over-saturate: IPA running down the capstan washes old lubricant out of the bearing.
* There is '''no service-adjustable speed control'''. Amstrad's only speed instruction is a check, not an adjustment.


=== Azimuth adjustment ===
=== Azimuth adjustment ===


This is Amstrad's own procedure, and it is worth doing properly because a misaligned head is indistinguishable from a tired tape.<ref name="sm464" />
Amstrad's procedure needs a test tape recorded with a constant 6&nbsp;kHz tone and a valve or electronic voltmeter:<ref name="sm464" />


Equipment: a test tape recorded with a '''constant 6 kHz tone''', and a valve/electronic voltmeter (Amstrad specifies a V.T.V.M.).
# Set the volume on the CPC 464 to maximum.
 
# Connect the voltmeter to pin 7 of IC302 on the cassette PCB.
# Set '''volume to maximum''' on the CPC464.
# Play the test tape and turn the azimuth screw on the cassette head for a reading between 330&nbsp;mV and 520&nbsp;mV.
# Connect the meter to '''pin 7 of IC302''' (the LA6324 on the cassette PCB).
# Play the test tape and adjust the '''azimuth screw on the cassette head''' to read between '''330 mV and 520 mV'''.


=== Speed check ===
=== Speed check ===


Put a standard tape in the mechanism and monitor the output on an oscilloscope, 100 µs range. Amstrad's tolerance statement is the useful part: '''a speed variation of ±4% will not affect software loading.'''<ref name="sm464" /> If you are within that, the belt and pinch roller are not your fault.
Play a standard tape and check the output on an oscilloscope on the 100&nbsp;µs range. Amstrad states that a speed variation of ±4% will not affect software loading. The manual gives no speed adjustment.<ref name="sm464" />


=== Testing the cassette module on its own ===
=== Testing the cassette board alone ===


The deck can be run independently of the CPU. Connect 5 V DC across points '''B(−)''' and '''C(+)''' on the cassette PCB and link '''E to G''' and '''H to F'''. The cassette will then operate in audio mode.<ref name="sm464" />
To run the cassette module without the computer, connect 5&nbsp;V DC across points B (−) and C (+) on the cassette PCB and link E to G and H to F; the deck then works in audio mode.<ref name="sm464" />


=== Amstrad's cassette fault chart ===
=== Amstrad's cassette fault chart ===


When tape loading fails, Amstrad's sequence is: '''check the connections to the tape deck → clean the tape head → check head alignment → check the switches on the cassette keys → check the tape motor control relay'''. If software loads but produces unusual results, the fault is on the computer board: RAM failure or ULA failure.<ref name="sm464" />
When tapes will not load, Amstrad's order is: check the connections to the tape deck, clean the tape head, check head alignment, check the switches on the cassette keys, and check the tape motor control relay. If software loads but behaves strangely, the fault is on the computer board, in the RAM or the ULA. A physically damaged tape will not load at all: "there will be no 'half' working programs."<ref name="sm464" />


'''A useful thing that is not a fault:''' Amstrad states plainly that physical damage to a software tape stops it loading altogether — "there will be no 'half' working programs. They either load — or they don't."<ref name="sm464" />
== Power input ==


== Power ==
The DC socket is J104, part 170024, described by Amstrad as a "5mm socket for CPC464 power supply".<ref name="sm464" /> Grimware gives the input as 5&nbsp;V at 2&nbsp;A on a 2.1&nbsp;mm plug.<ref name="grim464">Grimware, [https://www.grimware.org/doku.php/documentations/hardware/amstrad.cpc464 "Amstrad CPC 464"]. Retrieved 2026-10-01. Community hardware notes with the DC input rating, and pinouts of the printer, expansion, joystick and monitor connectors.</ref> Check the polarity of any replacement supply against your own board before connecting it. On an unreliable machine, measure 5&nbsp;V at J104 before suspecting anything on the board.


The machine takes '''5 V DC''' on a DC jack socket, '''J104''', Amstrad part number '''170024'''. Amstrad's specification describes it as a "5 mm socket for CPC464 power supply (supplied exclusively from screen system)"; community documentation gives the mating plug as 2.1 mm.<ref name="sm464" /><ref name="grim464">[https://www.grimware.org/doku.php/documentations/hardware/amstrad.cpc464 "Amstrad CPC464"], Grimware — hardware documentation for the CPC464 including the 5 V 2 A power requirement, the 2.1 mm DC plug, and the 50-way expansion connector pinout. Secondary source.</ref> The supply comes from the matching monitor, which contains a dedicated 5 V regulator stage for the computer.
== Connectors ==
 
If you intend to run the machine without an Amstrad monitor you need a stand-alone 5 V supply of adequate current. '''Check the polarity of your own board and your own plug before connecting anything''' — the CPC464's power connector CP001 feeds +5 V and 0 V straight to the rails, and Amstrad's circuit diagram shows no reverse-polarity protection diode on that input.<ref name="sm464" />
 
The first check on an unreliable machine — random crashes, failure to start — is '''5 V at J104''' with a meter, before suspecting anything on the board.
 
== Connector care ==


{| class="wikitable styled-table" style="width:100%; text-align:left;"
{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''CPC464 external connectors'''<ref name="sm464" />
|+'''CPC 464 external connectors'''
! Ref !! Amstrad description !! Part no. !! Notes
! Ref !! Amstrad description !! Part no. !! Notes
|-
|-
| '''J101''' || DIN socket, 6 pin || 170025 || RGB, sync, composite video and luminance+sync to the monitor. Bent pins are the common failure.
| J101 || DIN socket, 6 pin || 170025 || Monitor: 1 red, 2 green, 3 blue, 4 sync, 5 ground, 6 luminance<ref name="grim464" />
|-
|-
| '''J102''' || Joystick socket, 9 pin || 170023 || Amstrad's pin names: 1 UP, 2 DOWN, 3 LEFT, 4 RIGHT, 5 SPARE, 6 FIRE 2, 7 FIRE 1, 8 COMMON, 9 COM 2<ref name="sm464" /><ref name="grim464" />
| J102 || Joystick socket, 9 pin || 170023 || 1 up, 2 down, 3 left, 4 right, 5 fire 3, 6 fire 2, 7 fire 1, 8 ground, 9 ground for a second joystick<ref name="grim464" />
|-
|-
| '''J103''' || Input/Output socket, 3.5 mm || 170022 || Stereo sound output. Line level — not enough to drive headphones directly.
| J103 || Input/output socket, 3.5&nbsp;mm || 170022 || Stereo sound output, intended for an amplifier rather than headphones<ref name="grim464" />
|-
|-
| '''J104''' || DC jack socket || 170024 || 5 V in from the monitor
| J104 || DC jack socket || 170024 || 5&nbsp;V in from the monitor
|-
|-
| Printer port || PCB edge connector || — || 34 physical contacts, but wired to '''36-pin Centronics numbering''' with pins 18 and 36 absent — which is why Amstrad's own schematic labels it "36 way". Pin 9 is ground rather than D7, so the CPC has '''only 7 data bits'''; some printers need a converter.<ref name="cpcprn">[https://www.cpcwiki.eu/index.php/Connector:Printer_port "Connector: Printer port"], CPCWiki — documents that the 34-pin edge connector uses 36-pin Centronics numbering with pins 18 and 36 absent, and that pin 9 is ground (or logic low on late cost-down models), giving 7 data bits. Secondary source.</ref>
| Printer || PCB edge connector || – || Centronics-style; pin 9 is ground, so only seven data bits (D0–D6) are output<ref name="grim464" />
|-
|-
| Expansion port || PCB edge connector, 50 way || — || '''Pin 1 = SOUND''' (from the AY-3-8912), '''pin 27 = +5 V''', '''pin 49 = GND''', '''pin 50 = CPUCLK''' (4 MHz). The connector for the DDI-1 disc interface, ROM boxes and other add-ons.<ref name="sm464" /><ref name="grim464" />
| Expansion || PCB edge connector, 50 way || – || Pin 1 sound, 2 and 49 ground, 27 +5&nbsp;V, 50 CPU clock (4&nbsp;MHz); the DDI-1 disc interface plugs in here<ref name="grim464" />
|}
|}


Clean edge fingers and the mating contacts with a soft eraser or contact cleaner. The CPC's edge fingers are exposed at the back of the case with no cover, so they oxidise faster than most contemporaries.
== Capacitors ==
 
== Capacitor health ==


The CPC464 carries '''thirteen aluminium electrolytics''' in total. '''Only two of them are on the main board''' — C101 and C102, both 47 µF/10 V. The other eleven are all in the 300-series and live on the cassette PCB, including the largest, '''C322 (470 µF/10 V)'''.<ref name="sm464" /> Full values, circuit references and Amstrad part numbers: [[Amstrad CPC 464 Capacitor Replacement Guide]].
The CPC 464 has fourteen aluminium electrolytic capacitors. Only C101 and C102, both 47&nbsp;µF / 10&nbsp;V, are on the main board; the other twelve are 300-series parts on the cassette PCB, the largest being C322, 470&nbsp;µF / 10&nbsp;V.<ref name="sm464" /> Values, references and part numbers are in the [[Amstrad CPC 464 Capacitor Replacement Guide]].


The board also carries three '''polystyrene''' capacitors (C302, C305, C312). Polystyrene deforms at soldering temperatures an electrolytic shrugs off — if you replace one, work fast and keep the iron off the body.
== ROM ==


== ROM health ==
The operating system and Locomotive BASIC 1.0 are in a single 32 KB ROM at IC103, listed in the original parts list as TMM-23256P-1950.<ref name="sm464" /> CPCWiki lists Amstrad's custom part numbers for the CPC 464 firmware ROM as 40009 (English), 40037 (Spanish) and 40050 (French).<ref name="cpcparts" /> If the machine starts with corrupted characters or hangs, reseat IC103 before suspecting the chip.


The operating system and Locomotive BASIC 1.0 live in a single 32 KB mask ROM at '''IC103''', marked '''TMM-23256P-1950''', Amstrad service part '''170102'''.<ref name="sm464" /> The corresponding Amstrad custom-chip number is '''40009''' for the English-language firmware; '''40037''' is Spanish and '''40050''' French.<ref name="cpcparts">[https://www.cpcwiki.eu/index.php/Amstrad_part_numbers "Amstrad part numbers"], CPCWiki — catalogue of Amstrad 40xxx custom-chip numbers, including 40009 (CPC464 English firmware), 40037 (Spanish), 40050 (French), 40022 (CPC664 firmware) and 40015 (AMSDOS). Secondary source.</ref>
== DDI-1 disc drive ==


Mask ROM has no UV-degradation path and does not fail with age. The common ROM-related fault is a bad socket contact, not a bad chip. If the machine boots to corrupted characters or hangs at the prompt, reseat IC103 before suspecting it.
The DDI-1 and FD-1 drives each have their own mains supply, so they carry mains voltage even though the computer does not.<ref name="ddi">Amstrad Consumer Electronics plc, ''DDI1 / FD1 Service Manual'', p. 2 "Specifications" and p. 3 "Cabinet Parts List". Described at [[Amstrad DDI-1 / FD-1 Service Manual]].</ref> The mechanism is a belt-driven Compact FDD EME-150A, and Amstrad lists the drive belt as part 190015.<ref name="ddi" /> CPCWiki gives the replacement belt as 3&nbsp;mm wide, 0.6&nbsp;mm thick and 230&nbsp;mm in outer circumference, and warns that the small write-protect pin can fall out when the drive is turned over.<ref name="cpcbelt">CPCWiki, [https://www.cpcwiki.eu/index.php/Changing_the_drive_belt "Changing the drive belt"]. Retrieved 2026-10-01. Belt size, a removal procedure for the CPC 6128 that it says is nearly the same on the DDI-1, and the write-protect pin warning.</ref>


== Recommended tools ==
== Tools ==


* Philips screwdrivers and an anti-static strap.
* Cross-head screwdrivers and an anti-static strap
* Digital multimeter — the single most useful tool on this machine, because so many faults resolve to 5 V not arriving.
* Digital multimeter
* IPA and '''foam''' swabs for the cassette head and capstan.
* Isopropyl alcohol and foam swabs
* Oscilloscope and an electronic voltmeter, if you intend to do the azimuth and speed checks properly.
* Oscilloscope, electronic voltmeter and a 6&nbsp;kHz test tape for the azimuth and speed checks
* A 6 kHz constant-tone test tape.
* Replacement main belt, sized from your own pulleys
* Replacement main belt — measure your own pulleys; Amstrad publishes only the part number (170204).
* Fine-tip soldering iron and desoldering braid
* Fine-tip soldering iron and solder wick for capacitor work.
* A stand-alone 5 V supply, if you want to test the computer without its monitor.
* See [[Recommended Tools]] for the general workshop kit.
* See [[Recommended Tools]] for the general workshop kit.
== Technical specification ==
From Amstrad's own specification page.<ref name="sm464" />
{| class="wikitable styled-table" style="width:85%; text-align:left;"
|+'''CPC464 — Amstrad's published specification'''<ref name="sm464" />
! Item !! Figure
|-
| Processor || Z80A at 4 MHz
|-
| RAM / ROM || 64 KB RAM (over 42 KB available to the user) / 32 KB ROM
|-
| Video / sound / I/O || 6845 CRT controller · AY-3-8912 (3 voice, 7 octave) · 8255 parallel I/O
|-
| Keyboard || 74 keys
|-
| Keyboard unit || 580 × 70 × 170 mm, 2.4 kg
|-
| CTM640 monitor || 375 × 340 × 365 mm, 10.6 kg
|-
| GT64 monitor || 305 × 315 × 335 mm, 6.3 kg
|-
| Mains || 240 V AC 50 Hz — '''at the monitor'''; keyboard and datacorder are powered from the screen system
|}
'''There is no cooling fan.''' No fan or fan motor appears anywhere in Amstrad's parts lists, and the machine is passively cooled.<ref name="sm464" />


== Related pages ==
== Related pages ==


* [[Amstrad CPC 464]] · [[Amstrad CPC 464 Troubleshooting Guide]] · [[Amstrad CPC 464 Capacitor Replacement Guide]]
* [[Amstrad CPC 464]] · [[Amstrad CPC 464 Troubleshooting Guide]] · [[Amstrad CPC 464 Capacitor Replacement Guide]]
* '''[[Amstrad CPC 464 Service Manual]]''' — the source for the part numbers, alignment figures and fault charts on this page
* [[Amstrad CPC 464 Service Manual]] · [[Amstrad DDI-1 / FD-1 Service Manual]]
* [[Amstrad CPC 664]] — the successor, with a built-in 3-inch disc drive
* [[Amstrad CPC 664 Maintenance Guide]]
* [[Amstrad DDI-1 / FD-1 Service Manual]] — the external 3-inch disc option for the 464
* [[CRT Discharge Procedure]] · [[Capacitor Failure Symptoms]] · [[Recommended Tools]]
* [[CRT Discharge Procedure]] · [[Capacitor Failure Symptoms]] · [[Recommended Tools]]


== References ==
== References ==
<references />
<references />


Latest revision as of 09:13, 1 October 2026

CPC 464 with the CTM640 colour monitor, which holds the system's only power supply

Routine maintenance on the Amstrad CPC 464 centres on the cassette deck and its board, the keyboard, the connectors and the monitor that powers the machine. Fault diagnosis is in the Amstrad CPC 464 Troubleshooting Guide and component values are in the Amstrad CPC 464 Capacitor Replacement Guide. Part numbers and alignment figures are from Amstrad's service manual.[1]

Power and safety

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The CPC 464 has no mains connection and no power supply of its own. It takes 5 V DC through a socket on the back, which Amstrad's specification says is "supplied exclusively from screen", the CTM640 colour or GT64 green monitor.[1]

  • The keyboard unit carries no mains voltage. Work on it with the DC lead unplugged and anti-static precautions.
  • The monitors contain the mains supply and a CRT, and hold a dangerous charge after switch-off. Read CRT Discharge Procedure before opening one.
  • Amstrad's fault chart for a dead machine starts at the monitor: mains fuse, then the DC output and lead, then the computer.[1]

Amstrad's safety test for the monitors is a 4 kV flash test between the mains lead (live and neutral joined) and all accessible metal, and an insulation test between the same points requiring at least 4 MΩ.[1]

Identifying your board

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CPCWiki's catalogue of photographed boards identifies four CPC 464 main board versions by their silkscreened part number.[2]

CPC 464 main board versions
Version Silkscreen Size Notes
1 (©1983) Z70100; 270100 MC0001A; Z70100 MC0001A 405 × 155 mm Gate array under a cooling plate, its VCC2 fed through R138 and R139; keyboard wired to the board on the first boards
2 (©1984) Z70200 with MC0001A, MC0002A–D, MC0003A, MC0008B–D 405 × 152 mm Pads for both the old and new gate array; connector for the 6128-style 2 × 10-pin membrane keyboard
3 Z70374 MC0044A/B, Z70375 MC0044D, Z70378 MC0046A 240 × 150 or 238 × 145 mm Same parts packed more tightly; joystick and stereo sockets on the left
4, cost-down (©1988) Z80329 MC0099A 237 × 108 mm 100-pin surface-mount ASIC (Amstrad 40226) combining the gate array, CRTC and some floppy, DRAM and reset logic[3]

On the original board Amstrad's parts list gives the gate array as IC116, 20RA043, part 40007.[1] CPCWiki lists 40007 and 40008 as the heat-sinked gate arrays and 40010 as the later one without a heat sink, with different pinouts.[3]

Opening the unit

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  1. Switch off and unplug the DC lead from the monitor.
  2. Disconnect any joystick, printer or expansion-port device.
  3. Lay the keyboard unit face down on a soft cloth and remove the screws from the underside.
  4. Lift the case apart, minding the keyboard cable, and photograph the cable routing before you unplug anything.
  5. Disconnect the keyboard cable and the cassette board's 8-way connector, CD001.

Amstrad's cassette PCB drawing labels the CD001 conductors: 1 +B (red), 2 GND (black), 3 +B (white), 4 DATA IN (blue), 5 DATA OUT (green), 6 SOUND IN (white), 7 PLAY ON (yellow), 8 INPUT.[1]

The cassette PCB (PCB301) carries the audio and tape electronics: IC301 (LA4140), IC302 (LA6324 quad op-amp), the tape motor relay RY301, the 300-series resistors and twelve of the fourteen electrolytic capacitors. The volume control VR301 is on the small board PCB302 beside it.[1] Audio and tape faults are usually on these boards.

Cleaning

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  • Brush and low-pressure air for the main board, keyboard mat and cassette mechanism.
  • Clean the record/play head (part 170201), capstan and pinch roller with isopropyl alcohol on a foam swab.
  • Clean the sockets J101 to J104 with a little contact cleaner on a swab.[1]
  • Clean the rubber contact mats (parts 170008 key mat, 170009 digit mat, 170010 spacer) with a damp lint-free cloth.[1]

Keyboard

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The keyboard has 74 keys: QWERTY with a numeric cluster, cursor and copy cursor, large enter, shift, caps lock, tab, escape, delete, clear and control.[1] It is built from keytops, the rubber contact mats and a contact PCB in two halves (parts 170028 and 170029).[1] Amstrad's fault chart for keys that do not work sends you to inspect the keyboard PCB for cracks, liquid spillage and distorted mounting, and then to check the connector lead and its termination.[1]

Cassette deck

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CPC464 cassette mechanism, service parts (p. 6)
Part Amstrad part no.
Main belt 170204
R/P head 170201
Erase head 170202
Pinch roller assembly 809162
Spring, pinch roller 809161
Flywheel 809156
Idler assembly 809155
Idler gear 809173
Motor 170208
Motor pulley 170211
Counter belt (cabinet list) 170014
Cassette mechanism, complete (cabinet list) 170012

When the motor runs but the capstan does not turn, check the main belt (170204). Amstrad gives only the part number, not the belt's dimensions, so measure the pulleys before ordering a generic belt, and clean any residue of the old belt off the pulleys first.

Azimuth adjustment

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Amstrad's procedure needs a test tape recorded with a constant 6 kHz tone and a valve or electronic voltmeter:[1]

  1. Set the volume on the CPC 464 to maximum.
  2. Connect the voltmeter to pin 7 of IC302 on the cassette PCB.
  3. Play the test tape and turn the azimuth screw on the cassette head for a reading between 330 mV and 520 mV.

Speed check

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Play a standard tape and check the output on an oscilloscope on the 100 µs range. Amstrad states that a speed variation of ±4% will not affect software loading. The manual gives no speed adjustment.[1]

Testing the cassette board alone

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To run the cassette module without the computer, connect 5 V DC across points B (−) and C (+) on the cassette PCB and link E to G and H to F; the deck then works in audio mode.[1]

Amstrad's cassette fault chart

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When tapes will not load, Amstrad's order is: check the connections to the tape deck, clean the tape head, check head alignment, check the switches on the cassette keys, and check the tape motor control relay. If software loads but behaves strangely, the fault is on the computer board, in the RAM or the ULA. A physically damaged tape will not load at all: "there will be no 'half' working programs."[1]

Power input

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The DC socket is J104, part 170024, described by Amstrad as a "5mm socket for CPC464 power supply".[1] Grimware gives the input as 5 V at 2 A on a 2.1 mm plug.[4] Check the polarity of any replacement supply against your own board before connecting it. On an unreliable machine, measure 5 V at J104 before suspecting anything on the board.

Connectors

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CPC 464 external connectors
Ref Amstrad description Part no. Notes
J101 DIN socket, 6 pin 170025 Monitor: 1 red, 2 green, 3 blue, 4 sync, 5 ground, 6 luminance[4]
J102 Joystick socket, 9 pin 170023 1 up, 2 down, 3 left, 4 right, 5 fire 3, 6 fire 2, 7 fire 1, 8 ground, 9 ground for a second joystick[4]
J103 Input/output socket, 3.5 mm 170022 Stereo sound output, intended for an amplifier rather than headphones[4]
J104 DC jack socket 170024 5 V in from the monitor
Printer PCB edge connector – Centronics-style; pin 9 is ground, so only seven data bits (D0–D6) are output[4]
Expansion PCB edge connector, 50 way – Pin 1 sound, 2 and 49 ground, 27 +5 V, 50 CPU clock (4 MHz); the DDI-1 disc interface plugs in here[4]

Capacitors

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The CPC 464 has fourteen aluminium electrolytic capacitors. Only C101 and C102, both 47 µF / 10 V, are on the main board; the other twelve are 300-series parts on the cassette PCB, the largest being C322, 470 µF / 10 V.[1] Values, references and part numbers are in the Amstrad CPC 464 Capacitor Replacement Guide.

ROM

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The operating system and Locomotive BASIC 1.0 are in a single 32 KB ROM at IC103, listed in the original parts list as TMM-23256P-1950.[1] CPCWiki lists Amstrad's custom part numbers for the CPC 464 firmware ROM as 40009 (English), 40037 (Spanish) and 40050 (French).[3] If the machine starts with corrupted characters or hangs, reseat IC103 before suspecting the chip.

DDI-1 disc drive

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The DDI-1 and FD-1 drives each have their own mains supply, so they carry mains voltage even though the computer does not.[5] The mechanism is a belt-driven Compact FDD EME-150A, and Amstrad lists the drive belt as part 190015.[5] CPCWiki gives the replacement belt as 3 mm wide, 0.6 mm thick and 230 mm in outer circumference, and warns that the small write-protect pin can fall out when the drive is turned over.[6]

Tools

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  • Cross-head screwdrivers and an anti-static strap
  • Digital multimeter
  • Isopropyl alcohol and foam swabs
  • Oscilloscope, electronic voltmeter and a 6 kHz test tape for the azimuth and speed checks
  • Replacement main belt, sized from your own pulleys
  • Fine-tip soldering iron and desoldering braid
  • See Recommended Tools for the general workshop kit.
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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 1.10 1.11 1.12 1.13 1.14 1.15 1.16 1.17 1.18 Amstrad Consumer Electronics plc, CPC464 Micro Computer / CTM640 Colour Monitor / GT64 Green Monitor Service Manual. Described at Amstrad CPC 464 Service Manual. Technical specification and cabinet parts list p. 2; cassette mechanism parts list and alignment instructions p. 6; cassette PCB p. 7; basic hardware analysis p. 9; cassette and software analysis p. 10; electrical parts list p. 17.
  2. ↑ CPCWiki, "Mainboard Versions". Retrieved 2026-10-01. Community catalogue of board markings, sizes and per-version changes, compiled from photographed boards.
  3. ↑ 3.0 3.1 3.2 CPCWiki, "Amstrad part numbers". Retrieved 2026-10-01. Community list of Amstrad custom-chip and PCB numbers.
  4. ↑ 4.0 4.1 4.2 4.3 4.4 4.5 Grimware, "Amstrad CPC 464". Retrieved 2026-10-01. Community hardware notes with the DC input rating, and pinouts of the printer, expansion, joystick and monitor connectors.
  5. ↑ 5.0 5.1 Amstrad Consumer Electronics plc, DDI1 / FD1 Service Manual, p. 2 "Specifications" and p. 3 "Cabinet Parts List". Described at Amstrad DDI-1 / FD-1 Service Manual.
  6. ↑ CPCWiki, "Changing the drive belt". Retrieved 2026-10-01. Belt size, a removal procedure for the CPC 6128 that it says is nearly the same on the DDI-1, and the write-protect pin warning.


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