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Capacitor maps

ZX Spectrum 128 · Version 6K / 6U

The 128 board has fourteen electrolytics, all axial (one lead at each end). Values and voltages from the Sinclair parts list [1], with the µF confirmed on the redrawn schematics of version 6U [2] and in the Retroleum kit [3]. There is no board drawing: we measured the positions on a Version 2-1 board [5] and compared them with photos of a 6K and a 6U [6], so they are approximate. Always check the reference on the silkscreen.

14 capacitors

Before you start

  • Work with the transformer unplugged from the mains and from the board. The 128 uses an external 9 V power supply; if it is faulty, don't open it: the 230 V side is not something to open at home. Bring it to the shop.
  • There are no leaking SMD parts here, but axials dry out with age. The converter that generates the +12 V and −12 V for the RS232, the keypad and the expansion port (TR4, coil, C44 and C80) is the part that works hardest [1][2]. If the RS232 or the keypad doesn't work, start measuring there.
  • The replacement's voltage can be the same as or higher than the original, never lower. Sinclair used many 10 V parts [1], some on 9 V and 12 V lines (C50 on the 9 V input, C44 on the +12 V output [2]). On those, and in general, fit 16 V or 25 V: it works and lasts longer.
  • Mind the polarity. On axials the negative is on the side with the arrows and the positive is on the side with the rim [7]. Before removing each one, note which way round it was fitted.
  • If your kit includes a C131 and your board has no place for it, that is normal: it is on the 6U schematic [2] and in the Retroleum kit [3], but not in the Sinclair list [1] or on the Version 2-1 board we measured [5].
  • C28 is the one people usually swap for a 47 µF to reduce the vertical stripes on RGB, together with 1 µF ceramic C7 and C8 [4]. If you find lifted traces or damaged chips, bring the board to the shop.
RF modulatorRGB videoExpansion portPower (9 V)Z80A (IC2)ULA 7K010 (IC1)ROM (IC5)ZX8401 / PCF1306P (IC27)HAL10H8 (IC29)AY-3-8912 (IC32)RAM 4164Keyboard (KB1)Tape (MIC/EAR)Serial RS232Keypad
Axial electrolyticBoard seen from above, rear connectors at the top.Approximate positions: always check the reference printed on the board.

All capacitors

Ref.ValueVoltageTypeDiameter[n]
C25100 µF10 VAxial electrolytic[1][2][3]
C271 µF50 VAxial electrolytic[1][3]
C2822 µF10 VAxial electrolytic[1][3][4]
C3422 µF10 VAxial electrolytic[1][2][3]
C44100 µF10 VAxial electrolytic[1][2][3]
C45100 µF10 VAxial electrolytic[1][2][3]
C5022 µF10 VAxial electrolytic[1][2][3]
C744.7 µF5 VAxial electrolytic[1][2][3]
C8022 µF10 VAxial electrolytic[1][2][3]
C11147 µF16 VAxial electrolytic[1][2][3]
C11247 µF16 VAxial electrolytic[1][2][3]
C1231 µF10 VAxial electrolytic[1][2][3]
C1271 µF10 VAxial electrolytic[1][2][3]
C13147 µF16 VAxial electrolytic[2][3]

Shopping list

Quantities by value and voltage. Use new capacitors with the same capacitance and the same voltage or higher, that fit in the same space.

QtyValueVoltageTypeRef.
2×1 µF10 VAxial electrolyticC123, C127
1×1 µF50 VAxial electrolyticC27
1×4.7 µF5 VAxial electrolyticC74
4×22 µF10 VAxial electrolyticC28, C34, C50, C80
3×47 µF16 VAxial electrolyticC111, C112, C131
3×100 µF10 VAxial electrolyticC25, C44, C45

Sources

  1. [1]Spectrum 128 Service Manual (Bravemay Ltd para a Sinclair Research), tabela 5.2: componentes da placa principal · Sinclair Research, 1986
  2. [2]ZX Spectrum+ 128k: esquemas redesenhados, circuito analógico (rev 1.0a) e digital (rev 2.0), placa 6U · Ian Worsley, via Spectrum for Everyone, 2001
  3. [3]Capacitors for Spectrum 128 models: Replacement Electrolytic Capacitors for the "Toast Rack" Spectrum 128 · Retroleum
  4. [4]Fixing Vertical 'Jailbars' on your 48K, 128K and Grey Spectrum +2 · Spectrum for Everyone
  5. [5]Fotografia da placa do Spectrum 128 (128K Spectrum Version 2-1) · Planet Sinclair
  6. [6]ZX Spectrum Models: revisões Version 2, 2-1, 6K, 6U e 9G (com fotografias) · Spectrum for Everyone
  7. [7]Recapping your Spectrum · Spectrum for Everyone