Editing Sinclair ZX Spectrum +2 (section)

== How the +2A and +2B differ ==

The black '''+2A''' and '''+2B''' that followed are '''not''' minor restylings of the grey +2 — they are different machines built on the '''+3''' platform, and repair information does not carry across. The key differences:<ref name="sfe" />

* They use the '''Z70830''' board (shared with the +3, with the floppy components unpopulated) or the '''Z70833''', a cut-down board with the floppy area physically absent.
* Most of the ULA, discrete logic, PCF and 40057 functions are consolidated into a single '''Amstrad 40077''' gate array.
* The '''DC-DC converter is deleted'''. The rails come directly from a new power supply using a '''6-pin DIN''' connector instead of the 2.1 mm barrel jack — so grey +2 and +2A power supplies are '''not interchangeable'''.
* RAM changes from sixteen 64 Kbit × 1 devices to '''four 64 Kbit × 4''' devices.
* The split-bus arrangement moves inside the gate array, so external peripherals can no longer drive the keyboard.
* Contention matches the original 128 specification, which is why some software written on real 128/grey +2 hardware sounds wrong on a +2A.
* The Z70830 has a '''known audio design error''' causing heavily distorted output, corrected on the later Z70833.