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Capacitor maps · Z70830

ZX Spectrum +2A / +3 · Z70830 (ISSUE 1 e 2)

The Z70830 is the board of the +3 and the first +2A machines: Amstrad made a single board and built it in two ways [2][5]. It has few electrolytics, all radial: three 100 µF and four 1 µF on the +3, with values and voltages from the Amstrad list [1], confirmed on the redrawn schematic [2] and in the Retroleum kit [3]. The positions were measured on a photo of a Z70830 ISSUE 2 [4] and are approximate. Always check the reference on the silkscreen.

7 capacitors

Before you start

  • First of all, check which board you have. Most black +2A machines have the Z70833, which is a different board [5]; this map is only for the Z70830 (the number is printed on the board, next to the AMSTRAD logo).
  • The +2A and +3 power supply is external and provides several voltages (+5 V, +12 V and −12 V) through a DIN plug, and the board has no regulator: it receives the voltages ready-made [6]. Don't swap power supplies between models: the +2A one only gives 200 mA on the +12 V and the +3 needs 700 mA for the disk drive [6], and the 9 V supplies of the 128 and the grey +2 don't work with this plug. Don't open the power supply: the 230 V side is not something to open at home. Bring it to the shop.
  • Always work with the power supply unplugged from the mains and from the board. There are no leaking SMD parts: replace the electrolytics if they are bulging, leaking or if there are symptoms. Apply little heat and take your time, so as not to lift traces.
  • On the +2A built on this board, C41 is not fitted and C48, 1 µF, appears next to C38 [2], and the Retroleum kit for the +2A still has four 1 µF parts [3]. The Amstrad list we have is the +3 one and does not include C48 [1], so we don't put it on the map; a 1 µF 50 V part, like the others, is fine.
  • On ISSUE 1 the factory soldered parts on the underside of the board, including diodes connected to the negative of C41 [7]. When replacing C41 on an ISSUE 1, don't pull them off.
  • Mind the polarity of each one, and the voltage can be the same as or higher than the original, never lower. If you find lifted traces or damaged chips, bring the board to the shop.
RF modulatorRGB videoKeypad (AUX)Serial RS232Expansion portPower (DIN)Parallel (printer)External floppyInternal floppyKeyboard (Y)Tape (datacorder, +2A only)Gate array 40077 (IC1)Z80A (IC2)ROM 27256 (IC7, IC8)AY-3-8912 (IC11)RAM 4464 (IC5, IC6)RAM 4464 (IC3, IC4)µPD765 (IC16, +3 only)
Radial electrolyticBoard seen from above, rear connectors at the top.Approximate positions: always check the reference printed on the board.

All capacitors

Ref.ValueVoltageTypeDiameter[n]
C8100 µF16 VRadial electrolytic[1][2][3]
C131 µF50 VRadial electrolytic[1][2][3]
C271 µF50 VRadial electrolytic[1][2][3]
C29100 µF16 VRadial electrolytic[1][2][3]
C30100 µF16 VRadial electrolytic[1][2][3]
C381 µF50 VRadial electrolytic[1][2][3]
C411 µF50 VRadial electrolytic[1][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.
4×1 µF50 VRadial electrolyticC13, C27, C38, C41
3×100 µF16 VRadial electrolyticC8, C29, C30

Sources

  1. [1]Spectrum +3 Service Manual: Electrical Parts List e Printed Circuit Board Component Layout (Z70830 ISSUE 2) · Amstrad, 1987
  2. [2]ZX Spectrum +2A/+3 Schematic (Z70830), redesenho revisão 20, com as listas de componentes omitidos em cada modelo · Guesser, zxnet.co.uk, 2020
  3. [3]Capacitors for Spectrum 128 models: packs para o +2A (black case) e para o +3 (Z70830 / Z70835) · Retroleum
  4. [4]Fotografia da placa do Spectrum +3 (Z70830 ISSUE 2) · Planet Sinclair
  5. [5]ZX Spectrum +2A/2B, +3/3B: modelos e placas principais · Sinclair Wiki
  6. [6]Replacement PSU for +2A or +3 Machines · Spectrum for Everyone
  7. [7]Factory modifications to Amstrad built ZX Spectrums (Z70830 ISSUE 1) · zxnet.co.uk
  8. [8]Spectrum +2B/+3B Service Manual: Spectrum +2B Electrical Parts List (Z70833) · Amstrad