707
edits
ZX Spectrum +2A/2B, +3/3B: Difference between revisions
Jump to navigation
Jump to search
m
Fix typos
m (→+2B and +3B) |
m (Fix typos) |
||
| Line 40: | Line 40: | ||
=====+2B and +3B===== | =====+2B and +3B===== | ||
The +2A/+3 circuit contains a design flaw in the audio output circuitry which causes serious distortion to AY-3-8912 music. A new design was developed in 1988 with redesigned audio circuits and manufactured as the +2B and +3B. Unlike the +2A/+3, Amstrad did not create one common motherboard for these computers. Instead the +2B board is stepped on the right hand side to allow two boards to be | The +2A/+3 circuit contains a design flaw in the audio output circuitry which causes serious distortion to AY-3-8912 music. A new design was developed in 1988 with redesigned audio circuits and manufactured as the +2B and +3B. Unlike the +2A/+3, Amstrad did not create one common motherboard for these computers. Instead the +2B board is stepped on the right hand side to allow two boards to be panelled side by side and use a much smaller area (hence cheaper to produce) than two +2A/+3 boards. | ||
The identification of models is contested because Amstrad sold large numbers of computers with a Z70833 motherboard in cases bearing the +2A | The identification of models is contested because Amstrad sold large numbers of computers with a Z70833 motherboard in cases bearing the +2A designation. The change to shipping Z70833 boards instead of Z70830 boards appears to have happened fairly early on because most +2A cases encountered contain a Z70833. Z70830 motherboards populated as a +2A are consequently quite rare. | ||
The +2B motherboard is the Z70833 ISSUE 1 or 2 ©1988. There is also an ISSUE 4 ©1990 which has a different FM modulator circuit for the audio (no example of an ISSUE 3 board has surfaced which suggests none were ever produced/sold). | The +2B motherboard is the Z70833 ISSUE 1 or 2 ©1988. There is also an ISSUE 4 ©1990 which has a different FM modulator circuit for the audio (no example of an ISSUE 3 board has surfaced which suggests none were ever produced/sold). | ||