=== ZX Spectrum +2B and +3B ===
The ''ZX Spectrum +2B'' and ''ZX Spectrum +3B'' were functionally similar in design to the Spectrum +2A and +3.<ref>''Spectrum +2B/+3B Service Manual''. AMSTRAD.</ref> The main electronic differences being simply changes to the generation of the audio output signal to resolve problems with [[Clipping (audio)|clipping]] and the removal of the external tape loading input ("ear" pin).
Unlike the +2A the Spectrum +2B motherboard (AMSTRAD part number Z70833) does not have provision for floppy disk controller circuitry so cannot be assembled as a +3B. The +3B motherboard is Amstrad part number Z70835.