Amstrad PCW 8256 Capacitor Replacement Guide

The Amstrad PCW 8256 keeps its power supply on the monitor board, so the electrolytic capacitors that matter most for the whole machine, printer included, are in the monitor unit. Amstrad's service manual lists every electrolytic with its value, voltage and part number. The list of parts that differ on the Amstrad PCW 8512 contains no electrolytic capacitors, so the same list covers both machines.

PCW8256/8512 monitor board; the outlined area is at mains potential (service manual p. 21)

Safety

Warning: the monitor unit runs from the mains and contains a CRT. The 100 µF 400 V reservoir C5005 holds a dangerous charge after the plug is pulled.

• Unplug the machine, remove the back and discharge the tube; see CRT Discharge Procedure.
• Measure across C5005 and discharge it through a suitable resistor before touching the board. Amstrad's board drawing outlines the mains area and marks it "danger mains voltage".
• After the work, run Amstrad's safety tests: a 4 kV flash test, and an insulation resistance of at least 4 MΩ, both between the joined mains live and neutral and all accessible metal on the outside.

How the parts are numbered

Amstrad numbers parts in series by area. The 5000 series is the power supply (IC5001 STK7308, switching transformer T5001, mains fuse F5001); the 4000 series is the deflection circuit (IC4001 LA1385, IC4002 AN5753, horizontal drive transformer T4001); the 100 series is the CPU board (IC101–IC120); the 800 series is the keyboard (keyboard controller IC801); the 8000 series includes the CRT socket J8001; and the 2000 series includes the brightness control VR2001. The printer's own board uses the 700 series and has its own parts list.

Electrolytic capacitors

Electrolytic capacitors, monitor, CPU and keyboard (service manual p. 34)

Ref	Value	Voltage	Amstrad part no.
C5028	0.33 µF	50 V	171086
C4001	0.47 µF	50 V	150909
C803	1 µF	50 V	20062
C4029	1 µF	160 V	1422151
C5006	1 µF	250 V	1400152
C4006, C4020	4.7 µF	50 V	1400240
C122, C4010, C4015	10 µF	16 V	20024
C4032	10 µF	25 V	20037
C2001, C5020–C5023	10 µF	50 V	1400242
C4030	10 µF	160 V	170608
C4008	22 µF	16 V	20025
C8001	22 µF	63 V	170609
C4012	33 µF	10 V	170610
C5024	33 µF	50 V	171087
C121, C124, C805	47 µF	10 V	1400244
C4031	47 µF	50 V	171088
C2002	100 µF	16 V	20028
C5012	100 µF	50 V	171089
C5005	100 µF	400 V	171090
C4011	220 µF	10 V	170611
C4021, C4025, C4026, C4033	220 µF	16 V	20029
C5007	220 µF	35 V	20055
C5025	470 µF	10 V	20031
C5017, C5027	470 µF	16 V	1400248
C5018, C5026	470 µF	35 V	171091
C5019	470 µF	50 V	171092
C4014	1000 µF	10 V	800372

The same list gives two tantalum capacitors, C4007 (1 µF 50 V, 171100) and C4009 (10 µF 16 V, 1422167), and a 0.1 µF 250 V "special type" at C5001 (171102).

Electrolytic capacitors, printer board MS0030B (service manual p. 34)

Ref	Value	Voltage	Amstrad part no.
C719	47 µF	10 V	20027
C720	1000 µF	35 V	171207

The manual's short Mk II parts list changes the mains filter coil (L500), the switching transformer (T5001, part 171227), the vertical hold control and two ceramic resonators, and lists no different capacitors. Boards in the field may still differ from the drawings, so read the value and voltage printed on each part before removing it.

Where to start

The 5000-series electrolytics belong to the power supply, which feeds the whole machine including the printer. If the 12 V or 5 V output is low, noisy or will not adjust into tolerance, start with these. The 4000-series parts are in the deflection circuit. See Capacitor Failure Symptoms for what failed parts look like.

Procedure

1. Unplug the machine, remove the back of the monitor unit, and discharge the CRT and C5005.
2. Photograph the board and note the value, voltage and polarity of each electrolytic before removing it.
3. Remove each capacitor and clean the pads. Check under the larger supply capacitors for leaked electrolyte and corroded tracks.
4. Fit new parts of the same capacitance and the same or a higher voltage rating, observing polarity. For C5005, use a 400 V part.
5. Inspect and reflow any cracked joints on the switching transformer, the STK7308 and the other heavy parts.
6. Reassemble, then check and set the supply outputs before refitting the back.

After the recap

Set the supply outputs as Amstrad's alignment chart specifies, with connector CD101 disconnected and the brightness control VR2001 at maximum:

Supply settings (service manual p. 17)

Output	Measure at	Set with	Tolerance
12 V	Pin 2 of CD102	VR5002	±2%
5 V	Pin 3 of CD102	VR5001	±2%

Then reconnect CD101, check the picture adjustments in the Amstrad PCW 8256 Maintenance Guide, and repeat Amstrad's safety tests.

Related pages

• Amstrad PCW 8256 · Amstrad PCW 8256 Maintenance Guide · Amstrad PCW 8256 Troubleshooting Guide
• Amstrad PCW 8512 · Amstrad PCW 9256 Capacitor Replacement Guide
• Capacitor Failure Symptoms · CRT Discharge Procedure · Recommended Tools