Sinclair ZX spectrum 48K

Causes

 * Keyboard non functional

Solutions

 * Replaced decayed keyboard membrane

Opening the case
Firstly undo the 5 Philips head screws on the bottom then carefully lift the top case off while mindful of the keyboard ribbons as these can easily get torn.

Removing the keyboard membrane

 * To remove the old keyboard membrane after you have removed the top part of the case use a heat gun on the lowest setting to loosen up the adhesive under the metal plate to help prevent damage to the metal cover.
 * After removing the metal plate lift the rubber key mat off the shell and then slide the old membrane out.
 * To reassemble follow the steps in reverse and reattach the metal plate with new double sided tape.

Mainboard
This is the list for a issue two 48K PCB

This is the list for a issue 6A 48K PCB

Mainboard
Issue two 48K

Issue 6A 48K

If parts are not available or different selection is preferred, you can use the values in the Original Parts section to perform a parametric search.

Kits

 * Digikey BOM: https://www.digikey.com/

Related Links

 * https://spectrumforeveryone.com/wp-content/uploads/2017/08/ZX-Spectrum-Service-Manual.pdf