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Last modified on 6 March 2021, at 12:20

Keyboard Membrane Repair/Replacement Guide

The CPC keyboards contain fragile keyboard membranes, which have a rather low lifetime of maybe 5-10 years.

The east-german CPC clone KC Compact and apparently at least early CPC 464s as well contain a more robust real keyboard circuit board, which should give it an infinite lifetime.

Cleaning

Dual-foil membrane keyboards (as found in CPC 6128, CPC Plus, and 3rd generation CPC 464 keyboards) often only need to be cleaned.

Repair

Leitsilber 3g.jpg
Leitsilber L100.jpg

Broken wires are most often occuring on single-foil keyboards (as found in CPC 664, and 2nd generation CPC 464 keyboards). There is no chance to repair broken wires on the membrane by soldering (either the wire vaporizes, or the foil melts). However, one can repaint broken wires using conductive silver, which is sold as:

  • English: conductive silver (or conductive paint)
  • German: Leitsilber (or Silber Leitlack)
  • French: vernis conducteur / résine à l'argent / colle conductrice
  • Spanish/Catalan: pasta conductiva de plata o tinta conductiva

the silver should be available anywhere where you can buy electronic components. It may be also available as car equipment (for repairing the rear-window heating).

Replacement

New Membranes

New membranes are available for the CPC664 (as of December 2012), but no new ones are currently available for other CPCs. Old stocks of replacement membranes are however, still available for the CPC464+ and CPC6128+.

Adapters for PC Keyboards

The CPCKey circuit translates the serial PC Keyboard signals to CPC keyboard matrix signals (the circuit uses a lot of components though). A simplified solution may be a single chip with built-in microprocessor, flash memory, and I/O ports.

Rewired PC Keyboards

Cut all wires on the circuit board, and rewire them as in the CPCs keyboard matrix. Sounds simple, but it's quite a lot of work. Of course it works only with keyboards that do have a real circuit board, not with membrane based keyboards. Both expensive and inexpensive keyboards may contain either type.

Pictures

  • CPC 664 (single-foil)

  • CPC 6128 (dual-foil)

  • CPC Plus (dual-foil)

  • KC Compact with robust circuit board

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