Sinclair ZX Spectrum +2A and +2B

Introduction

The Spectrum +2A replaced the previous Spectrum +2 model in 1987 and was in fact the last Spectrum model made, being released after the Spectrum +3.

The case was restored to the traditional Spectrum black making it easily distinguishable from the old grey model.

Although it kept the same name, it sported a completely redesigned motherboard based around the new Amstrad +3 4.1 ROM model with a much reduced chip count. 

The board was very similar indeed to the +3 and essentially the +2A was a Spectrum +3 with a cassette deck replacing the disk drive (as can be seen from the reference to +3 BASIC in the start up menu).

The Spectrum +2A had two more 16K ROMs.  One held the second part of the reorganised 128 ROM and the other contained the +3's disk operating system which went unused of course on the the +2A and +2B. The two new ROMs and the original two 16K ROMs were physically combined into two 32K chips. The keypad scanning routines were also removed (not used since the days of the Spanish Spectrum+ 128).

Bank switching of memory was improved allowing the ROM to be paged out for another 16K of RAM at the bottom of the address space to permit the use of CP/M (on the Spectrum +3).

Several changes were also made on the bus and of course all this little lot caused many more incompatibilities with older software - even some written specifically for the 128K machines!

The Spectrum +2B had some minor board revisions over the +2A (the main board was at Issue 4 for the +2B), but the main thing of any significance was a move of manufacture to from Hong Kong to Taiwan. It was the last official Sinclair Spectrum model ever made.


Technical Details

  • CPU: Z80A
  • Speed: 3.5MHz
  • ROM: 64KB (32K for 128K mode, 16K for 48K mode, 16K for +3DOS)
  • RAM: 128KB (8 x 16K banks)
  • Full-stroke 58 key Keyboard (same layout as Spectrum+)
  • Colour Graphics
  • Sound - 3 Channels, 7 Octaves (Yamaha AY-3-8912)
  • RGB, RS232/Midi
  • Local price at launch: £200

Problems and Issues

Worn Drive Belt
The cassette mechanism on the +2A and +2B models was superior to that used on the earlier grey +2 model and generally more reliable.
However, the drive belt does does suffer the same "kink",  stretching and hardening with age as its predecessor on the original +2 and will certainly need changing if you have just bought a +2A.

The +2A and +2B models only have one belt, which is identical to the large belt on the Spectrum +2.


Other Cassette Unit Issues
All the cassette deck problems outlined in the Spectrum +2 section also apply to the Spectrum +2A and +2B - see the Spectrum +2 Technical Information page here.

If the cassette drive does prove to be faulty and you can't repair it,, don't be fooled by the the misleading labelling of the "Tape / Sound" port at the back of the +2A.

This suggests that an external cassette player can be connected via this port in the same way as it can with a Spectrum +3. It is not the case - the port on the +2A (and +2B) is wired only for sound out on the main board - it will not accept sound in.

Disk Drives
Don't expect to be able to connect an Amstrad external FD-1 or DDI-1 to the back of the computer as the interface advertised by Amstrad before its launch was never implemented.
The external interface which was available for the Amstrad CPC464 is not compatible either, so there is no way to attach an external 3" disk drive to this model.

All is not lost though if you're desperate for a disk drive - the Spectrum +3e ROMs from Garry Lancaster will work with the +2A which (with a suitable interface such as the DIVIDE or DIVMMC units) will allow you to connect a standard density IDE 3.5" disk drive, a hard drive or even a micro SD card drive.


See also the the Spectrum +2 Servicing and Repairs section for more comprehensive and detailed coverage of Spectrum +2 issues.

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