Sinclair ZX Spectrum 128


By 1985, sales of the Spectrum had started to slide and so the Spectrum+ was updated considerably to produce the Sinclair ZX Spectrum+ 128.

Although the new machine had the keyboard and case of the Spectrum+, internally it was a major upgrade.

A much upgraded sound system powered by the AY-3-8912 chip gave the new Spectrum three sound channels over seven octaves. A new PLAY command was added to 128 BASIC which could also control up to 8 channels of music via the new Midi port (also the same socket as the RS232 port).

There was 128K of RAM (which could be used as a RAM disk) and a new 128 BASIC which finally did away with the single key entry system

However there was a 48K compatibility mode which switched in the old 48K ROM for older games and conventional BASIC (if you could remember the key presses). Things weren't quite as clear as that though and the use of some previously unused (on the Spectrum 48K) ROM locations meant incompatibility for some software (mainly games) which relied on ROM routines.

Other niceties included were a full screen editor calculator and a built in Tape Tester.

Another key addition was video output to RGB or Composite monitors for much improved picture quality.

There was an optional add-on keypad, but these are very rare indeed - they may have only been released for the Spanish market where the 128+ was launched in September 1985.

The Spectrum+ 128 was finally released in February 1986, but by then Sinclair were in severe financial difficulties.

 A few months later, Amstrad took over Sinclair and the new 128 was quickly dropped as Amstrad consolidated operation and reviewed their combined model range..

 As such, the Spectrum 128 was only in the market place for a short time and sold only a comparatively few numbers, making them a little rare today and sought after by collectors.

Technical Details

  • CPU: Z80A
  • Speed: 3.5MHz
  • ROM: 32KB (16K for 128K mode, 16K for 48K mode)
  • RAM: 128KB (8 x 16K banks)
  • Rubber Keyboard
  • Colour Graphics
  • Sound - 3 Channels, 7 Octaves
  • RGB, Keypad, RS232/Midi
  • Local price at launch: £180

Problems and Issues

Keyboard Problems
Sharing the same case and keyboard assembly as the Spectrum+ 48K, keyboard issues frequently found with the smaller brother are all still present with the 128 as well!

Keyboard membrane and bubble mat issues are all covered in the Spectrum+ 48K section here.

Loose Cassette Connector Sockets
Another very common problem with all Spectrums using cassette leads are loose clamps inside the connector sockets.

This causes the leads to slip out of the socket, or move around affecting program loading or saving performance.

I usually have spare sockets in the Sinclair Shop pages here, but if your soldering skills aren't up to removing the old and fitting the new then a gentle push with a small screwdriver is often successful in re-tensioning the spring contact.

Overheating ULA
The ULA did tend to overheat and cause odd behaviour and such as freezing and crashes.  This led to the aluminium heat sink being fitted to the first Spectrum +2 models which used essentially the same ROM.


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