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.
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.
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).
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 soon dropped as they consolidated the operation. As such, the Spectrum+ 128 sold only a comparatively few numbers making them a little rare today and sought after by collectors.
Problems and Issues
Sharing the same case and keyboard assembly as the Spectrum+ 48K, keyboard issues frequently found with the smaller brother are all present with the 128 as well.
Keyboard membrane problems are probably the most common of the Spectrum+ faults and fortunately one of the easiest to put right. Unfortunately though, new membranes are expensive as they are larger and much more complex than the previous model's equivalent. Getting them manufactured these days in sensible numbers is not easy. There are a few people selling them, but quality is very variable - mine are very good (of course), but others, (especially those from Poland) are poor and I have had a lot of Spectrum+'s with new membranes sent to me for replacement.
Splits in the keyboard bubble mat can also cause similar problems, but the most common issues from worn out bubble mats are "spongy" feeling keys, or keys which do not spring back to where they should be (usually a fault caused by too many games of Daley Thompson's Supertest!).
New keyboard membranes and occasionally , bubble mats and keyboard assemblies themselves are usually available in the Sinclair Sales pages of the Sinclair section of the website and fairly easy to fit provided you have patience.
Detailed instructions on how to replace the membrane and/or bubble mat can be found in the Repairs & Servicing pages of the Sinclair section of the website here.
Be very careful when taking the cases apart for whatever reason - the case assemblies were made in various locations around the world with different quality plastics. Many are very soft and stripping the thread of the mounting posts when re-assembling is very easy indeed.
See the Sinclair ZX Spectrum+ 48K page of the Sinclair Repairs & Servicing section for instructions on replacing the membrane and bubble mat.
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 Sales pages of this Sinclair section of the website, but if your soldering skills aren't up to removing the old and fitting the new then a gentle push with a small flat blade screwdriver is often successful in re-tensioning the spring contact.
The ULA did tend to overheat and it is also now impossible to find should it die.
I occasionally have ULA's for the first Spectrum +2 model and to all intents and purposes, below that aluminium heatsink they are identical to the Spectrum+ 128. I have put these in many machines without problem.