Editing Sinclair ZX Spectrum 128 Capacitor Replacement Guide (section)

== The jailbars modification ==

Faint '''vertical banding on plain, light-coloured areas''', visible on the '''RGB output but not over RF or composite''', is a well-known Toastrack characteristic. It is a noise and ground-plane artefact, so an ordinary recap does not cure it. The established modification is:<ref name="jail">[https://spectrumforeveryone.com/technical/fixing-vertical-jailbars-48k-128k-spectrum/ "Fixing Vertical 'Jailbars' on your 48K, 128K and Grey Spectrum +2"], Spectrum for Everyone.</ref>

* Replace '''C28''' with a '''47 µF axial''' electrolytic in place of the original 22 µF. C28 sits to the right of the 5-way keyboard connector.
* Replace '''C7''' and '''C8''' with '''1 µF ceramic''' capacitors in place of the original 22 nF parts. These sit next to the IC12 and IC13 RAM devices at the bottom left of the board.

This significantly reduces the banding without eliminating it entirely. On the 48K machines the equivalent change is C5–C8 to 150–220 nF; on a grey [[Sinclair ZX Spectrum +2|+2]] it is C52.<ref name="jail" />