Amstrad PCW 9512+ Capacitor Replacement Guide

PCW9512+ monitor/CRT board MM0041A; the supply's electrolytics are in the 5000 series (service manual p. 18)

The Amstrad PCW 9512+ has its power supply on the monitor board, and the supply also powers the daisywheel printer. Amstrad's electrical parts list gives every electrolytic capacitor in the machine with value, voltage and part number: 29 entries covering 52 positions, plus two tantalum capacitors.

Safety

Warning: the main unit runs from the mains and contains a CRT. C5005, 150 µF 400 V, holds a dangerous charge after the plug is pulled.

• Unplug the machine 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 area at mains potential.
• After the work, run Amstrad's safety tests: a 4 kV flash test and an insulation resistance of at least 4 MΩ between the joined mains live and neutral and all accessible metal on the outside.

How the parts are numbered

The 5000 series is the power supply (IC5001 STK7309, the regulators IC5002–IC5005, switching transformer T5001, fuse F5001); the 4000 series is the deflection circuit (IC4001 LA1385, IC4002 AN5753, horizontal drive transformer T4001, flyback FB4001); the 700 series is the printer control circuit (IC701 AMS40088 and the hammer current control VR701); the 800 series is the keyboard (IC801 AMS40027); the 100 series is the main board logic and memory (IC102–IC126), with the processor at IC501; and the 8000 series includes the CRT socket J8001.

Electrolytic capacitors

PCW9512+ electrolytic capacitors (service manual, electrical parts list, PDF p. 30)

Ref	Value	Voltage	Amstrad part no.
C5027, C5031	0.33 µF	50 V	171086
C4001, C5022	0.47 µF	50 V	150909
C803, C5028, C5032	1 µF	50 V	20062
C4029	1.0 µF	160 V	1422151
C5006	1 µF	250 V	1400152
C4006, C4020	4.7 µF	50 V	1400240
C135, C713, C4010, C4024	10 µF	16 V	20024
C4032	10 µF	25 V	20037
C2001, C5023, C5025, C5029, C5033	10 µF	50 V	1400242
C4008	22 µF	16 V	20025
C8001, C8003	22 µF	63 V	170609
C4012	33 µF	10 V	170610
C134, C136, 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	150 µF	400 V	177147
C4011	220 µF	10 V	170611
C4021, C4025, C4033	220 µF	16 V	20029
C4026, C5007	220 µF	35 V	20055
C5024	470 µF	10 V	20031
C4035, C5034	470 µF	16 V	1400248
C5019, C5030	470 µF	35 V	171091
C4014	1000 µF	10 V	800372
C705	1000 µF	16 V	1400158
C706, C5021	1000 µF	25 V	177148
C707	1000 µF	35 V	1422159
C5018, C5026	2200 µF	25 V	177149
C701, C5020	2200 µF	35 V	1422160

The list also gives two tantalum capacitors: C4007, 1 µF 25 V (171100), and C4009, 10 µF 16 V (1422167). The PCW 8256/8512 list gives the same part number, 171100, for its C4007 but rates it at 50 V; read the part on the board before ordering.

Many of the 4000-series positions carry the same values and part numbers as on the PCW 8256's monitor board, for example C4011, C4012, C4014 and C4031. The supply is different: the 9512+ has 2200 µF capacitors at C5018, C5020 and C5026, and a 150 µF reservoir where the 8256 has 100 µF. The 700-series parts, including C701 (2200 µF 35 V) and C705–C707, are in the printer control circuit.

Where to start

The 5000-series parts belong to the power supply. If an output is low, noisy or out of reach of its adjuster, start with these, and with the 700-series parts if the printer misbehaves. See Capacitor Failure Symptoms for what failed parts look like.

Procedure

1. Unplug the machine, open the case, and discharge the CRT and C5005.
2. Photograph the boards 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 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. Use a 400 V part at C5005.
5. Inspect and reflow any cracked joints round T5001, the STK7309 and the heat-sinked regulators.
6. Reassemble, then check the supply outputs before refitting the cover.

After the recap

Check and set the outputs at connector A as Amstrad's chart specifies, with CP102 disconnected, VR401 at maximum and an electronic load on each output (Fig. 2-1 of the manual):

Supply settings (service manual p. 3)

Output	Load	Setting	Adjuster
24 V	1.2 A	24 V ±1.2 V	None; check only
12 V	1.2 A	12 V ±0.01 V	VR5002
5 V	1.8 A	5 V ±0.05 V	VR5001

Reconnect CP102, check the picture adjustments and the hammer current (VR701, 2.4 V pulse) in the Amstrad PCW 9512+ Maintenance Guide, and repeat the safety tests.

Related pages

• Amstrad PCW 9512+ · Amstrad PCW 9512+ Maintenance Guide · Amstrad PCW 9512+ Troubleshooting Guide
• Amstrad PCW 9256 Capacitor Replacement Guide · Amstrad PCW 8256 Capacitor Replacement Guide
• Capacitor Failure Symptoms · CRT Discharge Procedure · Recommended Tools