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Verification drive: flag unverified component data pending check against a primary source
Verified against Amstrad's own CPC664 Service Manual (hosted). Board is Z70205 MC0005A/B not Z70200/MC0030; drive is Matsushita EME-150A on PCB 30001 not 'Hitachi HD3.5R'; belt is 3x0.6x230mm not 54x1mm; OS ROM is part 40022 at IC103 not 40012; power is two 5mm DC connections not DIN-5; the 300-series caps are NOT absent on the 664. Added Amstrad's VR201 spindle-speed adjustment and mechanism procedures. Unverified data cleared.
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This guide documents preventive maintenance procedures for the '''[[Amstrad CPC 664]]''' (1985, Amstrad part number Z70200 / MC0030 family). The 664 inherits the keyboard, main PCB layout and audio chain of the [[Amstrad CPC 464|CPC 464]] and adds an integrated '''Hitachi-mechanism 3-inch floppy drive''' with a NEC uPD765A FDC and a 16 KB AMSDOS ROM. Almost all of the [[Amstrad CPC 464 Maintenance Guide|CPC 464 maintenance procedures]] apply equally to the 664; this guide concentrates on the floppy-drive maintenance, drive belt replacement, head alignment and AMSDOS ROM care that are specific to the 664 / 6128 family.
Preventive maintenance for the '''[[Amstrad CPC 664]]''' (1985), concentrating on the built-in 3-inch disc drive, which is what makes the 664 different from the [[Amstrad CPC 464|CPC 464]]. Fault diagnosis is in the [[Amstrad CPC 664 Troubleshooting Guide]]; component values are in the [[Amstrad CPC 664 Capacitor Replacement Guide]].


== Safety Warning ==
The 664 had an unusually short life. It was on sale from '''May to August 1985''' before the 6128 replaced it, which is why it is scarcer than either the 464 or the 6128, and why the community knowledge base around it is thinner.<ref name="cpcwiki664">[https://www.cpcwiki.eu/index.php/CPC664 "CPC664"], CPCWiki, citing ''Amstrad Action'' issue 1 (October 1985) page 8 for the May–August 1985 production window. CPCWiki gives no production figure for the 664 and none was found elsewhere. Secondary source.</ref> The keyboard, audio chain and most of the main board are shared with the 464, so the [[Amstrad CPC 464 Maintenance Guide|CPC 464 maintenance procedures]] apply to everything outside the disc subsystem.


Same as the CPC 464: the '''system unit''' itself runs on regulated 5 V DC (and +12 V on the 664 for the drive motor) supplied by the matching monitor. There is no mains voltage inside the system unit; capacitor work on the main PCB and the disc-controller area is low-risk.
Part numbers, circuit references and alignment figures here are Amstrad's own, from the [[Amstrad CPC 664 Service Manual]] hosted on this wiki.<ref name="sm664">Amstrad Consumer Electronics plc, ''CPC664 Micro Computer / CTM644 Colour Monitor / GT65 Green Monitor Service Manual''. Hosted at [[Amstrad CPC 664 Service Manual]]. Source for the CPC664 Basic Hardware Analysis (page 4), Software Errors (page 7), Diagnostic Flow Chart (pages 8–11), Alignment Checks including test points and the EME-CF2 test disk (pages 12–15), the Electrical Parts List (page 21), the Mechanism drawing and Mechanical Replacements procedures (page 37) and the Technical Specification (back page).</ref>


The '''CTM-644 / GT-64 / GT-65 monitor''' contains the CRT (15&ndash;25 kV anode) and mains-rectified bulk capacitors. Treat as lethal until measured otherwise &mdash; see [[Amstrad CPC 464 Maintenance Guide]] for the CRT discharge procedure.
== ⚠️ The monitor is the power supply ==


== Identifying Your Unit ==
Like the 464, '''the CPC 664 has no mains connection and no internal power supply.''' Amstrad's specification lists two separate DC connections on the back of the machine: a '''5 mm socket for the CPC664 5 V supply from the monitor''', and a '''5 mm plug and lead that goes out to the 12 V (disc) power socket on the monitor'''.<ref name="sm664" /> The CTM644 colour monitor and GT65 green monitor provide both.


Most CPC 664 main PCBs are silkscreened with one of the following part-number ranges. The PCB rev is essentially identical across production:
In the parts list these are '''J301''' (DC jack, Amstrad part 170024 — the same part as the 464's J104) and '''CD301''' (DC cord, part 170822).<ref name="sm664" /> There is no five-pin DIN power connector on this machine; the 5-pin DIN on the back (J302, part 170819) is the '''external cassette recorder''' socket, and the 3.5 mm socket (J103) is stereo audio out.<ref name="sm664" />


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Consequences for servicing:
{| class="wikitable styled-table" style="width:100%; text-align:center;"
 
|+'''Amstrad CPC 664 main PCB revisions'''
* '''The computer is safe to open.''' No mains inside the keyboard unit.
! Silkscreen marking !! Gate Array !! CRTC type !! Notes
* '''The monitor is not.''' CRT anode charge and mains-derived bulk capacitors persist after switch-off — see [[CRT Discharge Procedure]].
* '''A drive that will not spin is very often a 12 V problem, not a drive problem.''' The 12 V comes down a separate lead from the monitor, and that lead is a single point of failure. Check it before opening the drive.
 
== Identifying your board ==
 
The CPC 664 main board is '''Z70205''', 475 × 155 mm, in two variants:<ref name="cpcwikimb">[https://www.cpcwiki.eu/index.php/Mainboard_Versions "Mainboard Versions"], CPCWiki. Community catalogue of silkscreen markings, board dimensions and per-version differences across the CPC range. Gives the CPC664 board as Z70205 / MC0005A and MC0005B, and notes the MC0005B's unlabelled patch resistor R160. Secondary source, compiled from observed boards.</ref>
 
{| class="wikitable styled-table" style="width:95%; text-align:left;"
|+'''Amstrad CPC 664 main PCB variants'''<ref name="cpcwikimb" />
! Silkscreen !! Notes
|-
| '''Z70205 MC0005A''' || 8-pin FDC data separator
|-
| '''Z70205 MC0005B''' || German Schneider boards. Usually carries a patch resistor '''R160''' between pin 9 (A0) and pin 14 (/CASADDR) of IC105, which is not labelled on the PCB — do not mistake it for a previous owner's bodge
|}
 
'''Z70200 is a CPC 464 board, not a 664 board.'''<ref name="cpcwikimb" /> If your board is marked Z70200 you are looking at a 464.
 
Amstrad's parts list gives the key devices:<ref name="sm664" />
 
{| class="wikitable styled-table" style="width:95%; text-align:left;"
|+'''CPC664 — principal devices'''<ref name="sm664" />
! Ref !! Device !! Amstrad part no. !! Role
|-
| IC103 || TMM-23256P-1952 || '''40022''' || 32 KB OS + Locomotive BASIC 1.1 ROM
|-
| IC204 || TMM-23128P-1951 || '''40015''' || 16 KB AMSDOS ROM
|-
| IC111 || Z8400APS || 40080 || Z80A CPU
|-
| IC116 || HSG3130 / HSG3170 || '''40010''' || Gate Array
|-
| IC108 || HD6845SP || 170106 || CRTC
|-
| IC107 || M5L8255AP-5 || 170105 || Parallel I/O
|-
| IC102 || AY-3-8912 || 40001 || Sound generator
|-
| IC117–IC124 || HM4864U-2 || 170110 || 64 KB DRAM, eight 64K × 1 devices
|-
| '''IC201''' || '''µPD765AC''' || 40018 || Floppy disc controller
|-
|-
| Z70200 / MC0030 (most common UK / EU 1985) || 40010 (CMOS) or 40007 (Ferranti, heatsinked) || HD6845SP (Type 0) || Original 1985 production
| '''IC202''' || '''FDC9216BT''' || 40020 || Data separator
|-
|-
| Z70200 / MC0030 later runs || 40010 || HD6845SP (Type 0) or UM6845R (Type 1) || Late 1985 production after 6128 launch
| IC301 || LA4140 || 170111 || Audio power amplifier
|-
|-
| Schneider CPC 664 boards || same chip set as Amstrad, Schneider Computer Division part-number stamp || Type 0 or Type 1 || DACH region
| IC302 || LA63585 || 170814 || Cassette read chain
|}
|}


The 664 cabinet (parts 170301 family for the Amstrad UK version) is a flat all-in-one design with the keyboard at the front and the floppy drive bay at the rear-right. There is no cassette deck (vs the CPC 464) and no separate disc interface box (vs the CPC 464 + DDI-1).
== Opening the unit ==
 
Tools: a Philips screwdriver and an anti-static strap.
 
# Switch off and disconnect both DC leads from the monitor — the 5 V feed and the 12 V lead.
# Disconnect joystick, printer and expansion-port peripherals.
# Lay the keyboard face-down on a soft cloth and remove the underside screws.
# Lift the case halves apart carefully; take photographs as you go rather than relying on memory.
# Disconnect the disc drive cable. Amstrad's parts list calls the drive lead '''CD201''' (part 170821). Note pin 1 orientation before unplugging.
# Disconnect the keyboard cable.
 
'''The 664 keeps the cassette interface even though it has no cassette deck.''' IC301 (LA4140), IC302 (LA63585), the tape motor relay RY301, the speaker SP301, the volume control and the whole 300-series component population are all present, feeding the 5-pin DIN socket J302 for an external recorder.<ref name="sm664" /> If you have read elsewhere that the 300-series capacitors are absent on a 664, that is wrong — Amstrad's own parts list has C301, C303, C304, C306, C308, C309, C311, C314, C315, C316 and C317 all fitted.<ref name="sm664" />


== Opening the System Unit ==
== The disc drive ==


Tools: Philips #1 and #2 screwdriver, anti-static strap.
=== What is actually fitted ===


# Power off the system and unplug the DC power from the monitor.
Amstrad's specification describes the drive as "a 3" system, conforming to the Hitachi/Panasonic standard", software-configured for a '''12 ms step rate and 30 ms settling time'''.<ref name="sm664" /> The mechanism fitted is from the Matsushita '''EME''' series — the CPC664 and the early DDI-1 and CPC6128 used the '''EME-150A''' on PCB '''30001''', which is the PCB number Amstrad's own service manual refers to throughout.<ref name="sm664" /><ref name="cpcfdd">[https://www.cpcwiki.eu/index.php/Amstrad_FDD_part "Amstrad FDD part"], CPCWiki — catalogue of the Matsushita EME-series 3-inch mechanisms Amstrad fitted: EME-150A (PCB 30001, 1984 to early 1985, CPC664 / early DDI-1 / early 6128), EME-155 (PCB 30002), EME-156 (PCB Z70312), EME-156V (PCB Z80264) and the 5 V-only EME-157 (PCB Z80425). All single-sided, 40 track, 180 KB per side, 300 rpm. Secondary source.</ref> Later machines in the family used the EME-155, EME-156 and EME-156V. All are single-sided, 40 track, 180 KB per side, 300 rpm, and all except the late EME-157 need both 5 V and 12 V.<ref name="cpcfdd" />
# Disconnect joystick, printer and expansion-port peripherals.
# Place the keyboard face-down on a soft cloth.
# Remove all screws on the underside of the case (typically 6&ndash;8).
# Lift the lower case carefully. The floppy drive and the keyboard membrane are both clipped to the upper case; the main PCB is on the lower case.
# Disconnect the floppy drive ribbon from the main PCB at the disc-controller area (typically a 26-pin or 34-pin header). Note pin 1 orientation &mdash; the red-striped wire goes to the pin marked '1' on both ends.
# Disconnect the keyboard ribbon at CP002.
# Optionally remove the floppy drive: 4 screws hold it to the upper case.


The floppy drive uses Hitachi part-number HD3.5R or HD3.5-1 (the Hitachi 3-inch single-sided mechanism, the same one used in the Amstrad CPC 6128 and the Sinclair ZX Spectrum +3). Replacement units can be sourced from another non-working 664 / 6128 / Spectrum +3, or modern hardware substitutes (Gotek + FlashFloppy firmware, Hxc emulator) can be fitted in the same bay using a 3-inch-to-Hxc adapter cable.
The '''FD-1''' is the second-drive add-on for the 664, using the same mechanism family.<ref name="sm664" /> A 3-inch disc is double-sided in the physical sense — both surfaces are usable, and each side has its own reusable write-protect clip — but the drive only reads the side facing it, so you flip the disc by hand.<ref name="sm664" />


== Regular Cleaning ==
=== Amstrad's own position on the mechanism ===


* Soft brush + low-pressure compressed air for the main PCB, the disc-controller area, the keyboard mat and the floppy drive head area.
Printed twice in the manual, in a box: '''"Service Agents must not carry out any repair or adjustment to the Drive mechanism and its associated PCB 30001 during warranty. Faulty mechanism must be returned to AMSTRAD for exchange."'''<ref name="sm664" /> That was Amstrad's commercial policy in 1985, not a statement that the drive is unserviceable. It does mean the manual gives '''no component values for the drive PCB''' — the parts list carries the matching note that no part numbers are given for any part on that PCB.<ref name="sm664" /> What it ''does'' give is the mechanical parts breakdown, the alignment checks and the replacement procedures below, all of which remain usable.
* Clean the floppy R/W head with isopropyl alcohol on a foam swab. Do not use cotton-tipped swabs &mdash; cotton fibres in the head gap are a known cause of CRC errors and intermittent read failures.
* Clean the audio jack (J103), the 6-pin DIN video output (J101), the printer edge connector, the expansion edge connector and the joystick port (J102) with deoxidising contact cleaner sparingly on a foam swab.
* Clean the keyboard rubber-contact mats and the keyboard contact PCB as per [[Amstrad CPC 464 Maintenance Guide]] &mdash; the parts are identical.


== Floppy Drive Maintenance ==
=== Mechanism parts ===


The Hitachi 3-inch drive in the CPC 664 has three known wear items:
Amstrad's exploded view numbers the following:<ref name="sm664" />
 
{| class="wikitable styled-table" style="width:80%; text-align:left;"
|+'''CPC664 3-inch drive mechanism'''<ref name="sm664" />
! No. !! Part
|-
| 1 || Head Assembly
|-
| 2 || Stepper Motor
|-
| 3 || Stepper Motor Rotation Bolt
|-
| 4 || Spindle Motor
|-
| 5 || Flywheel
|-
| 6 || Pulley
|-
| 7 || Read/Write Protect / Index / LED P.C.B.
|-
| 8 || Track 00 Sensor Assembly
|-
| 9 || Spring
|-
| 10 || Loading Unit
|}
 
The drive belt runs on the underside of the loading unit, from the '''pulley (6)''' on the spindle motor to the '''flywheel (5)'''.


=== Drive belt ===
=== Drive belt ===


The drive belt is a thin (0.5 mm) flat rubber band that drives the disc spindle from a small pulley on the spindle motor. After 30+ years, the original belt is almost universally either liquefied (a sticky black residue on both pulleys) or stretched past usable tension. This is by far the most common 664 fault.
'''The perished belt is the characteristic 664 fault.''' After thirty-odd years the original is usually either liquefied into black gum on both pulleys or stretched past useful tension. Symptom: the motor runs, the disc does not spin, and the machine reports a read failure on a known-good disc.
 
Amstrad publishes no belt dimensions. The community specification for the CPC664 / 6128 / FD-1 3-inch drive belt is '''3 mm wide, 0.6 mm thick, 230 mm outer circumference''' — often advertised as "115 mm", which is the flat length.<ref name="cpcbelt">[https://www.cpcwiki.eu/index.php/Changing_the_drive_belt "Changing the drive belt"], CPCWiki — gives the replacement belt as 3 mm wide, 0.6 mm thick and 230 mm outer circumference (commonly advertised as 115 mm), with the removal procedure. Secondary source; Amstrad published no belt dimensions.</ref> '''Measure your own pulleys before ordering.'''
 
Procedure, following Amstrad's own spindle-motor sequence:<ref name="sm664" />
 
# Remove the drive from the case and take off the top cover.
# If the old belt has liquefied, clean both pulleys thoroughly with IPA. New belts will not grip through the residue.
# Fit the new belt over pulley and flywheel, and turn it by hand to confirm it sits centred and does not slip.
# '''Check the index period afterwards.''' Amstrad's spindle-motor procedure ends with "adjust VR201 so index frequency is 200 ± 2 ms" — see below.
 
=== Spindle speed — VR201 ===
 
This is the single most useful thing in the 664 manual and it is widely missed: '''the spindle speed is adjustable, on the drive's own control PCB, at VR201.'''<ref name="sm664" />


Symptom: '''disc not detected'''. The drive motor runs but the disc does not spin, or spins for a fraction of a second and stops. The system reports "Read fail" or hangs at CAT.
* Target: '''index period 200 ± 1 ms''' in the diagnostic flow chart, '''200 ± 2 ms''' in the spindle-motor replacement procedure. 200 ms is one revolution at 300 rpm.
* If the motor rotates but the period is out and '''VR201 will not bring it in''', Amstrad's chart sends you to substitute a known-good motor: if the drive then runs correctly, replace the motor; if not, replace the drive.
* If the motor does not rotate at all, check that power is arriving before anything else.


Procedure:
Set the speed after any belt change. A belt that grips but runs slow decodes as read errors, not as a mechanical fault.
# Remove the floppy drive from the case.
# Remove the drive's metal top cover (2&ndash;4 screws).
# Locate the rubber belt running between the spindle motor pulley (at the front-left of the drive) and the disc spindle pulley (at the centre).
# If the original belt has liquefied, clean both pulleys thoroughly with IPA on a swab. The liquefied residue is a sticky black gum that can stop the new belt from gripping.
# Slip the new belt onto both pulleys. Modern replacement belts for the CPC 664 / 6128 / +3 are available from dedicated Amstrad shops &mdash; '''54 mm &times; 1 mm flat rubber drive belt''' is the most common spec, but verify by direct measurement of the pulleys.
# Verify the belt sits centred on both pulleys, and rotate by hand to confirm there is no slip.


=== Pinch roller and head pressure ===
=== Stepper and head ===


Less common than the belt but eventually relevant. The pinch roller is the small rubber wheel that presses the disc against the spindle when a disc is inserted. After many disc insertions, the rubber hardens and develops flat spots, causing the disc to slip at high speed.
* The head carriage runs on a rod, moved by the stepper through a lead screw. Amstrad's head-replacement procedure involves removing the control PCB, unplugging the stepper and LED PCB, freeing the loading unit, then sliding the head off the rod — and it ends with '''"check alignment of Azimuth Burst / Track 00 Positioning"'''.<ref name="sm664" /> Do not take the head off casually.
* After replacing the stepper motor, '''index and positioning must be checked and amended as necessary'''.<ref name="sm664" />
* The '''Track 00 sensor assembly (8)''' is an optical part. Dust in it produces a track-0 fault that looks like a stepper failure.


* Replacement pinch rollers for the Hitachi mechanism are available as modern silicone-rubber parts.
=== Alignment checks ===
* Head load pressure: the head is sprung-loaded; do not adjust the spring tension by bending the bracket &mdash; the alignment is set at the factory and is not field-adjustable.


=== Worm drive / stepper lubrication ===
Amstrad gives a real alignment procedure. Equipment: a '''double-beam oscilloscope''' and the '''EME-CF2''' test disk.<ref name="sm664" />


The stepper motor moves the head radially across the disc via a fine-pitch worm-drive lead screw. The worm drive needs '''light machine oil''' (e.g. clock oil or sewing-machine oil) every 5&ndash;10 years. Symptom of dried lubrication: stepper makes a chattering sound and the head fails to seek properly, often reporting "Track 0 error" or "Disk error" when accessing a known-good disc.
{| class="wikitable styled-table" style="width:85%; text-align:left;"
|+'''Amstrad's alignment checks'''<ref name="sm664" />
! Check !! Track used
|-
| Radial adjustment || Track 19
|-
| Adjustment of the index burst || Track 39
|-
| Azimuth check || Track 39
|}


Procedure:
{| class="wikitable styled-table" style="width:85%; text-align:left;"
# Remove the drive's top cover.
|+'''Drive test points'''<ref name="sm664" />
# Locate the worm drive (a 2&ndash;3 mm-diameter threaded brass rod connecting the stepper motor to the head carriage).
! TP !! Signal
# Apply a single drop of clock oil to the lead screw at the head carriage end and the stepper end.
|-
# Move the head fully in and out by hand a few times to distribute the oil.
| TP1, TP2 || Read signal of filter outlet
# Avoid getting oil on the head itself or on any belt or pulley.
|-
| TP3, TP11 || Signal ground
|-
| TP5 || Track 00 sensor output
|-
| TP9 || Index signal
|}


== Head Alignment ==
Amstrad's framing is worth repeating: '''"If the wave patterns do not appear this confirms a fault with the mechanism. Before attempting any replacement check these waveforms thoroughly."'''<ref name="sm664" />


The Hitachi 3-inch drive has factory-set head alignment that does not normally drift. Alignment is checked with a calibrated alignment disc (commercially '''Dysan 224/2A''' was the contemporary standard; modern equivalents are rare). For most field service:
In practice, for a machine you are restoring rather than servicing under warranty: alignment rarely drifts on its own. If the drive reads commercial discs but not discs you wrote on another machine, the ''other'' machine is the misaligned one. Work through belt, speed, head cleanliness and the Track 00 sensor before suspecting alignment.


* If the drive reads commercial diskettes reliably but fails to read user-formatted diskettes, the user-format diskettes were probably written by a misaligned drive. Reformat fresh diskettes from the suspect drive and test those.
=== Head cleaning ===
* If the drive cannot read any commercial diskettes, suspect: drive belt (most common), head dirt, stepper lubrication, or in rare cases the head itself failed. Alignment is the last suspect.


If alignment is genuinely off, the procedure requires a service-grade alignment disc, a service-grade oscilloscope and the Hitachi alignment procedure from the drive service manual. This is normally beyond field service and the drive is typically retired in favour of a replacement.
IPA on a '''foam''' swab. Do not use cotton — fibres in the head gap cause CRC errors and intermittent reads. Amstrad's note in the error section is blunt: "Always ensure the head is clean."<ref name="sm664" />


== AMSDOS ROM Care ==
== AMSDOS ROM ==


The CPC 664 fits a separate '''16 KB AMSDOS ROM''' (Amstrad part number 40015) at a dedicated socket on the main PCB, in addition to the main 32 KB OS+BASIC ROM at IC103 (40012). AMSDOS is the firmware that implements disc I/O and the |&nbsp;(bar) commands.
AMSDOS lives in a separate 16 KB ROM at '''IC204''' (TMM-23128P-1951, Amstrad part '''40015'''), alongside the 32 KB OS+BASIC ROM at IC103 (part 40022).<ref name="sm664" />


Common issues:
* '''Socket contact failure''' is the common AMSDOS fault, not chip failure. Mask ROMs do not degrade. Reseat before suspecting anything.
* '''AMSDOS ROM socket loose''': remove the ROM, clean the socket pins with IPA, refit firmly. Symptom: system boots to BASIC but CAT, LOAD"!", etc. report "ROM not present" or hang.
* '''Unexpected disc behaviour is almost never the ROM.''' Check the disc, the drive cable and the mechanism first.
* '''AMSDOS ROM corrupted''': mask ROMs do not fail with age; if AMSDOS reports unexpected behaviour, suspect a bad disc, a bad drive cable, or a CRT/screen-corruption issue presenting as fake error messages. Verify by booting with a known-good test disc.
* Community-developed replacements (ROMDOS, PARADOS) fit the same socket and add features such as larger formats and faster access.
* '''Bypass / replacement''': community-developed ROM-based replacements for AMSDOS (e.g. ROMDOS, PARADOS) can be loaded into the AMSDOS socket. These add features such as 80-track double-sided support, larger directory entries, and faster sector access.


== Power Supply ==
== Capacitor health ==


The CPC 664 takes '''5 V DC at 2 A''' and '''+12 V DC at &asymp;0.6 A''' through the DC cord from the matching monitor. The CTM-644 colour monitor and the GT-65 green monitor both supply both rails on a multi-pin DC plug.
The CPC664 carries '''twelve aluminium electrolytics''' across five values, and '''five polystyrene''' capacitors. Values, circuit references and Amstrad part numbers: [[Amstrad CPC 664 Capacitor Replacement Guide]].


Unlike the 464 (which uses a single-pin 2.1 mm DC plug), the 664 / 6128 use a '''DIN-5 power cable''' or a stereo-3.5 mm-style multi-conductor cable, depending on the monitor.
Note two things:


If using a third-party display, a stand-alone '''5 V/2 A + 12 V/1 A''' dual-output PSU is required. The 12 V rail powers the floppy drive motor and stepper; the system unit and the floppy drive logic both run on 5 V.
* The 664's ceramic decoupling runs '''C101–C128 and C201–C213''' — the 200-series is the disc interface section, which the 464 does not have.<ref name="sm664" />
* '''Amstrad gives no values for anything on the drive's own PCB 30001.'''<ref name="sm664" /> Anything you read elsewhere claiming specific capacitor values for the 664's drive board did not come from Amstrad. Read them off your own board.


== Connector Care ==
The polystyrene capacitors (C302, C305, C312, C318, C319) deform at soldering temperatures an electrolytic tolerates easily. Work quickly and keep the iron off the body.


* '''Floppy drive ribbon''': the connector at the drive end is a 26-pin or 34-pin BERG header. Pin 1 is marked with a red stripe on the ribbon. Always align stripe-to-stripe; reversing the cable does not normally damage the drive but the drive will not respond.
== Regular cleaning ==
* '''AMSDOS ROM socket''': inspect the IC socket for bent pins or oxidation. Reseat the ROM if disc commands are unreliable.
* '''Drive power tap''': on most 664s the drive power comes from the same connector as the main PCB power. If the drive motor fails to spin, verify +12 V at the drive power connector with a multimeter.
* '''Expansion port''' (50-pin PCB edge): same as CPC 464 with the exception that internal FDC means /EXP-FDC handshake is now slightly different.


== Capacitor Health ==
* Soft brush and low-pressure air for the main PCB, the disc-controller area and the keyboard mat.
* Clean the drive head with IPA on a foam swab.
* Clean the 6-pin DIN video socket, the 9-pin D joystick socket, the 3.5 mm audio socket, the 5-pin DIN cassette socket and the printer and expansion edge connectors with contact cleaner sparingly on a foam swab.
* Keyboard rubber mats and contact PCB: identical to the 464, and the [[Amstrad CPC 464 Maintenance Guide]] procedure applies unchanged.


The 664 main PCB inherits all the [[Amstrad CPC 464 Capacitor Replacement Guide|CPC 464 capacitors]] in the non-cassette area, with the following changes:
== Recommended tools ==


* '''Cassette sub-PCB caps (C301, C303, C304, C306, C322, C315) are absent''' on the 664 because there is no cassette deck.
* Philips screwdrivers and an anti-static strap.
* The disc-controller area adds bypass capacitors near the NEC uPD765A FDC, near the AMSDOS ROM socket, and on the drive power input. Specific designators vary by board run; the most-failing positions in field service are the '''470 µF/16 V''' on the drive +12 V input and the '''10 µF / 22 µF''' caps near the FDC chip.
* Digital multimeter — the 12 V disc feed is the first thing to check on a non-spinning drive.
* Oscilloscope, ideally double-beam, if you intend to use Amstrad's alignment checks.
* IPA and '''foam''' swabs.
* Replacement drive belt — measure your own pulleys; the community figure is 3 mm × 0.6 mm × 230 mm.
* Small trim tool for VR201.
* A known-good 3-inch disc for testing.
* Fine-tip soldering iron and solder wick for capacitor work.
* A Gotek with FlashFloppy, or an HxC, if the original mechanism is beyond economic repair.
* See [[Recommended Tools]] and [[Floppy Drive Repair]].


Full list with values and recap procedure: [[Amstrad CPC 664 Capacitor Replacement Guide]].
== Technical specification ==


== Recommended Tools ==
From Amstrad's own specification page.<ref name="sm664" />


* Philips #1 and #2 screwdrivers.
{| class="wikitable styled-table" style="width:90%; text-align:left;"
* Anti-static strap.
|+'''CPC664 — Amstrad's published specification'''<ref name="sm664" />
* Digital multimeter.
! Item !! Figure
* IPA + foam swabs for head and connector cleaning.
|-
* '''54 mm &times; 1 mm flat rubber drive belt''' (or measured equivalent).
| Processor || Z80A at 4 MHz
* Modern silicone replacement pinch roller for the Hitachi 3-inch mechanism.
|-
* Clock oil for the stepper worm drive.
| RAM / ROM || 64 KB RAM (over 41 KB available to the user) / 32 KB ROM for BASIC and OS
* Soldering iron with fine tip + solder wick for capacitor work.
|-
* 3-inch test diskette known to be good (an "Amsoft Demo" disc or a community-archived disc image).
| Video / sound / I/O || 6845 CRT controller · AY-3-8912 (3 voice, 8 octave) · 8255 parallel I/O
* Optional: Gotek + FlashFloppy or Hxc emulator if the original Hitachi mechanism is beyond repair.
|-
| Keyboard || 74 keys
|-
| Disc drive || 3 inch, 12 ms step rate, 30 ms settling time, maximum 2 drives
|-
| Disc formats || Single sided, double density, 512-byte sectors, 40 tracks, 2:1 interleave. '''SYSTEM''' 9 sectors/track, 2 reserved tracks, 169 KB · '''DATA''' 9 sectors/track, no reserved tracks, 178 KB · '''IBM''' 8 sectors/track, 1 reserved track, 154 KB
|-
| Expansion || Up to 252 additional 16 KB ROMs
|-
| Keyboard unit || 580 × 70 × 170 mm, 2.4 kg
|-
| CTM644 monitor || 375 × 340 × 365 mm, 10.6 kg
|-
| GT65 monitor || 305 × 315 × 335 mm, 6.3 kg
|-
| Mains || 240 V AC 50 Hz — '''at the monitor'''; keyboard and disc drive power both come from the screen system
|}


== Related Pages ==
== Related pages ==


* [[Amstrad CPC 664]]
* [[Amstrad CPC 664]] · [[Amstrad CPC 664 Troubleshooting Guide]] · [[Amstrad CPC 664 Capacitor Replacement Guide]]
* [[Amstrad CPC 664 Troubleshooting Guide]]
* '''[[Amstrad CPC 664 Service Manual]]''' — the source for the part numbers, alignment figures and procedures on this page
* [[Amstrad CPC 664 Capacitor Replacement Guide]]
* [[Amstrad CPC 464 Maintenance Guide]] — the keyboard, audio and cleaning sections apply unchanged to the 664
* [[Amstrad CPC 464 Maintenance Guide]] &mdash; the keyboard and audio sections apply identically to the 664
* [[Amstrad DDI-1 / FD-1 Service Manual]] — the same 3-inch drive family, as the external unit
* [[Recommended Tools]]
* [[Floppy Drive Repair]] · [[CRT Discharge Procedure]] · [[Capacitor Failure Symptoms]] · [[Recommended Tools]]


== References ==
== References ==


* [https://archive.org/details/Amstrad_CPC664_Service_Manual_1985_Amstrad_Consumer_Electronics Amstrad CPC664 Service Manual] (1985, Amstrad Consumer Electronics). Authoritative source for the disc drive parts list, the disc-area schematic and the electrical parts list.
<references />
* [https://www.amstrad-noob.com/2020/02/08/replacing-the-fdd-drive-belt-on-the-new-cpc-664/ Replacing the FDD drive belt on the new CPC 664], Amstrad noob. Field-experience source for the drive belt replacement procedure.
* [https://www.cpcwiki.eu/index.php/Service_Manuals Service Manuals], CPCWiki. Index of CPC service-manual PDFs including the 664-specific volumes.


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{{Navbox-Amstrad|state=collapsed}}

Revision as of 19:17, 22 September 2026

Preventive maintenance for the Amstrad CPC 664 (1985), concentrating on the built-in 3-inch disc drive, which is what makes the 664 different from the CPC 464. Fault diagnosis is in the Amstrad CPC 664 Troubleshooting Guide; component values are in the Amstrad CPC 664 Capacitor Replacement Guide.

The 664 had an unusually short life. It was on sale from May to August 1985 before the 6128 replaced it, which is why it is scarcer than either the 464 or the 6128, and why the community knowledge base around it is thinner.[1] The keyboard, audio chain and most of the main board are shared with the 464, so the CPC 464 maintenance procedures apply to everything outside the disc subsystem.

Part numbers, circuit references and alignment figures here are Amstrad's own, from the Amstrad CPC 664 Service Manual hosted on this wiki.[2]

⚠️ The monitor is the power supply

Like the 464, the CPC 664 has no mains connection and no internal power supply. Amstrad's specification lists two separate DC connections on the back of the machine: a 5 mm socket for the CPC664 5 V supply from the monitor, and a 5 mm plug and lead that goes out to the 12 V (disc) power socket on the monitor.[2] The CTM644 colour monitor and GT65 green monitor provide both.

In the parts list these are J301 (DC jack, Amstrad part 170024 — the same part as the 464's J104) and CD301 (DC cord, part 170822).[2] There is no five-pin DIN power connector on this machine; the 5-pin DIN on the back (J302, part 170819) is the external cassette recorder socket, and the 3.5 mm socket (J103) is stereo audio out.[2]

Consequences for servicing:

  • The computer is safe to open. No mains inside the keyboard unit.
  • The monitor is not. CRT anode charge and mains-derived bulk capacitors persist after switch-off — see CRT Discharge Procedure.
  • A drive that will not spin is very often a 12 V problem, not a drive problem. The 12 V comes down a separate lead from the monitor, and that lead is a single point of failure. Check it before opening the drive.

Identifying your board

The CPC 664 main board is Z70205, 475 × 155 mm, in two variants:[3]

Amstrad CPC 664 main PCB variants[3]
Silkscreen Notes
Z70205 MC0005A 8-pin FDC data separator
Z70205 MC0005B German Schneider boards. Usually carries a patch resistor R160 between pin 9 (A0) and pin 14 (/CASADDR) of IC105, which is not labelled on the PCB — do not mistake it for a previous owner's bodge

Z70200 is a CPC 464 board, not a 664 board.[3] If your board is marked Z70200 you are looking at a 464.

Amstrad's parts list gives the key devices:[2]

CPC664 — principal devices[2]
Ref Device Amstrad part no. Role
IC103 TMM-23256P-1952 40022 32 KB OS + Locomotive BASIC 1.1 ROM
IC204 TMM-23128P-1951 40015 16 KB AMSDOS ROM
IC111 Z8400APS 40080 Z80A CPU
IC116 HSG3130 / HSG3170 40010 Gate Array
IC108 HD6845SP 170106 CRTC
IC107 M5L8255AP-5 170105 Parallel I/O
IC102 AY-3-8912 40001 Sound generator
IC117–IC124 HM4864U-2 170110 64 KB DRAM, eight 64K × 1 devices
IC201 µPD765AC 40018 Floppy disc controller
IC202 FDC9216BT 40020 Data separator
IC301 LA4140 170111 Audio power amplifier
IC302 LA63585 170814 Cassette read chain

Opening the unit

Tools: a Philips screwdriver and an anti-static strap.

  1. Switch off and disconnect both DC leads from the monitor — the 5 V feed and the 12 V lead.
  2. Disconnect joystick, printer and expansion-port peripherals.
  3. Lay the keyboard face-down on a soft cloth and remove the underside screws.
  4. Lift the case halves apart carefully; take photographs as you go rather than relying on memory.
  5. Disconnect the disc drive cable. Amstrad's parts list calls the drive lead CD201 (part 170821). Note pin 1 orientation before unplugging.
  6. Disconnect the keyboard cable.

The 664 keeps the cassette interface even though it has no cassette deck. IC301 (LA4140), IC302 (LA63585), the tape motor relay RY301, the speaker SP301, the volume control and the whole 300-series component population are all present, feeding the 5-pin DIN socket J302 for an external recorder.[2] If you have read elsewhere that the 300-series capacitors are absent on a 664, that is wrong — Amstrad's own parts list has C301, C303, C304, C306, C308, C309, C311, C314, C315, C316 and C317 all fitted.[2]

The disc drive

What is actually fitted

Amstrad's specification describes the drive as "a 3" system, conforming to the Hitachi/Panasonic standard", software-configured for a 12 ms step rate and 30 ms settling time.[2] The mechanism fitted is from the Matsushita EME series — the CPC664 and the early DDI-1 and CPC6128 used the EME-150A on PCB 30001, which is the PCB number Amstrad's own service manual refers to throughout.[2][4] Later machines in the family used the EME-155, EME-156 and EME-156V. All are single-sided, 40 track, 180 KB per side, 300 rpm, and all except the late EME-157 need both 5 V and 12 V.[4]

The FD-1 is the second-drive add-on for the 664, using the same mechanism family.[2] A 3-inch disc is double-sided in the physical sense — both surfaces are usable, and each side has its own reusable write-protect clip — but the drive only reads the side facing it, so you flip the disc by hand.[2]

Amstrad's own position on the mechanism

Printed twice in the manual, in a box: "Service Agents must not carry out any repair or adjustment to the Drive mechanism and its associated PCB 30001 during warranty. Faulty mechanism must be returned to AMSTRAD for exchange."[2] That was Amstrad's commercial policy in 1985, not a statement that the drive is unserviceable. It does mean the manual gives no component values for the drive PCB — the parts list carries the matching note that no part numbers are given for any part on that PCB.[2] What it does give is the mechanical parts breakdown, the alignment checks and the replacement procedures below, all of which remain usable.

Mechanism parts

Amstrad's exploded view numbers the following:[2]

CPC664 3-inch drive mechanism[2]
No. Part
1 Head Assembly
2 Stepper Motor
3 Stepper Motor Rotation Bolt
4 Spindle Motor
5 Flywheel
6 Pulley
7 Read/Write Protect / Index / LED P.C.B.
8 Track 00 Sensor Assembly
9 Spring
10 Loading Unit

The drive belt runs on the underside of the loading unit, from the pulley (6) on the spindle motor to the flywheel (5).

Drive belt

The perished belt is the characteristic 664 fault. After thirty-odd years the original is usually either liquefied into black gum on both pulleys or stretched past useful tension. Symptom: the motor runs, the disc does not spin, and the machine reports a read failure on a known-good disc.

Amstrad publishes no belt dimensions. The community specification for the CPC664 / 6128 / FD-1 3-inch drive belt is 3 mm wide, 0.6 mm thick, 230 mm outer circumference — often advertised as "115 mm", which is the flat length.[5] Measure your own pulleys before ordering.

Procedure, following Amstrad's own spindle-motor sequence:[2]

  1. Remove the drive from the case and take off the top cover.
  2. If the old belt has liquefied, clean both pulleys thoroughly with IPA. New belts will not grip through the residue.
  3. Fit the new belt over pulley and flywheel, and turn it by hand to confirm it sits centred and does not slip.
  4. Check the index period afterwards. Amstrad's spindle-motor procedure ends with "adjust VR201 so index frequency is 200 ± 2 ms" — see below.

Spindle speed — VR201

This is the single most useful thing in the 664 manual and it is widely missed: the spindle speed is adjustable, on the drive's own control PCB, at VR201.[2]

  • Target: index period 200 ± 1 ms in the diagnostic flow chart, 200 ± 2 ms in the spindle-motor replacement procedure. 200 ms is one revolution at 300 rpm.
  • If the motor rotates but the period is out and VR201 will not bring it in, Amstrad's chart sends you to substitute a known-good motor: if the drive then runs correctly, replace the motor; if not, replace the drive.
  • If the motor does not rotate at all, check that power is arriving before anything else.

Set the speed after any belt change. A belt that grips but runs slow decodes as read errors, not as a mechanical fault.

Stepper and head

  • The head carriage runs on a rod, moved by the stepper through a lead screw. Amstrad's head-replacement procedure involves removing the control PCB, unplugging the stepper and LED PCB, freeing the loading unit, then sliding the head off the rod — and it ends with "check alignment of Azimuth Burst / Track 00 Positioning".[2] Do not take the head off casually.
  • After replacing the stepper motor, index and positioning must be checked and amended as necessary.[2]
  • The Track 00 sensor assembly (8) is an optical part. Dust in it produces a track-0 fault that looks like a stepper failure.

Alignment checks

Amstrad gives a real alignment procedure. Equipment: a double-beam oscilloscope and the EME-CF2 test disk.[2]

Amstrad's alignment checks[2]
Check Track used
Radial adjustment Track 19
Adjustment of the index burst Track 39
Azimuth check Track 39
Drive test points[2]
TP Signal
TP1, TP2 Read signal of filter outlet
TP3, TP11 Signal ground
TP5 Track 00 sensor output
TP9 Index signal

Amstrad's framing is worth repeating: "If the wave patterns do not appear this confirms a fault with the mechanism. Before attempting any replacement check these waveforms thoroughly."[2]

In practice, for a machine you are restoring rather than servicing under warranty: alignment rarely drifts on its own. If the drive reads commercial discs but not discs you wrote on another machine, the other machine is the misaligned one. Work through belt, speed, head cleanliness and the Track 00 sensor before suspecting alignment.

Head cleaning

IPA on a foam swab. Do not use cotton — fibres in the head gap cause CRC errors and intermittent reads. Amstrad's note in the error section is blunt: "Always ensure the head is clean."[2]

AMSDOS ROM

AMSDOS lives in a separate 16 KB ROM at IC204 (TMM-23128P-1951, Amstrad part 40015), alongside the 32 KB OS+BASIC ROM at IC103 (part 40022).[2]

  • Socket contact failure is the common AMSDOS fault, not chip failure. Mask ROMs do not degrade. Reseat before suspecting anything.
  • Unexpected disc behaviour is almost never the ROM. Check the disc, the drive cable and the mechanism first.
  • Community-developed replacements (ROMDOS, PARADOS) fit the same socket and add features such as larger formats and faster access.

Capacitor health

The CPC664 carries twelve aluminium electrolytics across five values, and five polystyrene capacitors. Values, circuit references and Amstrad part numbers: Amstrad CPC 664 Capacitor Replacement Guide.

Note two things:

  • The 664's ceramic decoupling runs C101–C128 and C201–C213 — the 200-series is the disc interface section, which the 464 does not have.[2]
  • Amstrad gives no values for anything on the drive's own PCB 30001.[2] Anything you read elsewhere claiming specific capacitor values for the 664's drive board did not come from Amstrad. Read them off your own board.

The polystyrene capacitors (C302, C305, C312, C318, C319) deform at soldering temperatures an electrolytic tolerates easily. Work quickly and keep the iron off the body.

Regular cleaning

  • Soft brush and low-pressure air for the main PCB, the disc-controller area and the keyboard mat.
  • Clean the drive head with IPA on a foam swab.
  • Clean the 6-pin DIN video socket, the 9-pin D joystick socket, the 3.5 mm audio socket, the 5-pin DIN cassette socket and the printer and expansion edge connectors with contact cleaner sparingly on a foam swab.
  • Keyboard rubber mats and contact PCB: identical to the 464, and the Amstrad CPC 464 Maintenance Guide procedure applies unchanged.
  • Philips screwdrivers and an anti-static strap.
  • Digital multimeter — the 12 V disc feed is the first thing to check on a non-spinning drive.
  • Oscilloscope, ideally double-beam, if you intend to use Amstrad's alignment checks.
  • IPA and foam swabs.
  • Replacement drive belt — measure your own pulleys; the community figure is 3 mm × 0.6 mm × 230 mm.
  • Small trim tool for VR201.
  • A known-good 3-inch disc for testing.
  • Fine-tip soldering iron and solder wick for capacitor work.
  • A Gotek with FlashFloppy, or an HxC, if the original mechanism is beyond economic repair.
  • See Recommended Tools and Floppy Drive Repair.

Technical specification

From Amstrad's own specification page.[2]

CPC664 — Amstrad's published specification[2]
Item Figure
Processor Z80A at 4 MHz
RAM / ROM 64 KB RAM (over 41 KB available to the user) / 32 KB ROM for BASIC and OS
Video / sound / I/O 6845 CRT controller · AY-3-8912 (3 voice, 8 octave) · 8255 parallel I/O
Keyboard 74 keys
Disc drive 3 inch, 12 ms step rate, 30 ms settling time, maximum 2 drives
Disc formats Single sided, double density, 512-byte sectors, 40 tracks, 2:1 interleave. SYSTEM 9 sectors/track, 2 reserved tracks, 169 KB · DATA 9 sectors/track, no reserved tracks, 178 KB · IBM 8 sectors/track, 1 reserved track, 154 KB
Expansion Up to 252 additional 16 KB ROMs
Keyboard unit 580 × 70 × 170 mm, 2.4 kg
CTM644 monitor 375 × 340 × 365 mm, 10.6 kg
GT65 monitor 305 × 315 × 335 mm, 6.3 kg
Mains 240 V AC 50 Hz — at the monitor; keyboard and disc drive power both come from the screen system

References

  1. ↑ "CPC664", CPCWiki, citing Amstrad Action issue 1 (October 1985) page 8 for the May–August 1985 production window. CPCWiki gives no production figure for the 664 and none was found elsewhere. Secondary source.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 2.16 2.17 2.18 2.19 2.20 2.21 2.22 2.23 2.24 2.25 2.26 2.27 2.28 2.29 Amstrad Consumer Electronics plc, CPC664 Micro Computer / CTM644 Colour Monitor / GT65 Green Monitor Service Manual. Hosted at Amstrad CPC 664 Service Manual. Source for the CPC664 Basic Hardware Analysis (page 4), Software Errors (page 7), Diagnostic Flow Chart (pages 8–11), Alignment Checks including test points and the EME-CF2 test disk (pages 12–15), the Electrical Parts List (page 21), the Mechanism drawing and Mechanical Replacements procedures (page 37) and the Technical Specification (back page).
  3. ↑ 3.0 3.1 3.2 "Mainboard Versions", CPCWiki. Community catalogue of silkscreen markings, board dimensions and per-version differences across the CPC range. Gives the CPC664 board as Z70205 / MC0005A and MC0005B, and notes the MC0005B's unlabelled patch resistor R160. Secondary source, compiled from observed boards.
  4. ↑ 4.0 4.1 "Amstrad FDD part", CPCWiki — catalogue of the Matsushita EME-series 3-inch mechanisms Amstrad fitted: EME-150A (PCB 30001, 1984 to early 1985, CPC664 / early DDI-1 / early 6128), EME-155 (PCB 30002), EME-156 (PCB Z70312), EME-156V (PCB Z80264) and the 5 V-only EME-157 (PCB Z80425). All single-sided, 40 track, 180 KB per side, 300 rpm. Secondary source.
  5. ↑ "Changing the drive belt", CPCWiki — gives the replacement belt as 3 mm wide, 0.6 mm thick and 230 mm outer circumference (commonly advertised as 115 mm), with the removal procedure. Secondary source; Amstrad published no belt dimensions.


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