Sinclair ZX Spectrum +2 128K

Introduction

The ZX Spectrum +2 was Amstrad's first Spectrum, coming shortly after their purchase of the Spectrum range and "Sinclair" brand in 1986.

Launched in early 1987, the machine featured an all-new grey case featuring a proper spring-loaded keyboard (at last), dual joystick ports, and a built-in cassette recorder dubbed the "Datacorder".

Following on quickly from the dropping of the Spectrum 128, the Amstrad influence was obvious with its design being similar to the CPC464.

However, the built in cassette deck apart, the inernals, in most respects, were identical to the Spectrum 128 it replaced.

The main menu screen lacked the Spectrum 128's "Tape Test" option, and the ROM was altered to account for a new 1986 Amstrad copyright message.

These (and other) slight changes resulted in minor incompatibility problems with software that accessed ROM routines at certain addresses (this had been sorted to a certain degree by the time the Issue 2 boards were fitted in machines.


The new keyboard did not include the BASIC keyword markings that were found on earlier Spectrums, except for the keywords LOAD, CODE and RUN which were useful for loading software.

This was not a major issue however, as the +2 boasted a menu system, almost identical to the ZX Spectrum 128, where one could switch between 48k BASIC programming with the keywords, and 128K BASIC programming in which all words (keywords and otherwise) must be typed out in full (although the keywords are still stored internally as one character each).

Despite these changes, the layout remained identical to that of the 128.

Built in Taiwan, it became the first "Sinclair" product to be built outside the UK. However, with Amstrads greater emphasis on quality control, it was far more reliable than any of the earlier generation Spectrums.

Production costs were lower and the retail price dropped to £149 soon after launch.


Technical Details

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

Problems and Issues

Worn Drive belts
Immediate problems often experienced with a Spectrum +2 which hasn't been used for a long time are usually related to poor program loading performance.

Over time without use, the main drive belt develops a pronounced and very visible (when you turn the pulley) kink where it has been parked stationary over the drive motor capstan wheel. This can cause poor loading performance as the belt "skips" each time the kink passes over the capstan.  The belts also stretch with age and loose their elasticity which causes them to slip.

Replacing the belt is a simple task and we always have them available in the Sinclair section of the website shop. Instructions are available in the Repairs & Servicing section here, including advice on how to check the azimuth (head alignment) and how to cure other cassette loading issues.

The small belt rarely gives problems even now, and certainly doesn't seem to perish in the same way. They are available in the Sinclair Sales section of the shop if you need a replacement though.

Dirty Heads
If your +2 has been in storage in a dusty or dirty environment, the read / write heads will also be dirty.

Clean the heads with a cotton bud (or better, a low loss pointed head cleaning bud or chamois stick) soaked in a few drops of head cleaner (available in the shop).

Pause mechanism
Another common problem is the main drive wheel catching on a the small spring loaded pause mechanism pad positioned just below it. This causes the speed to fluctuate and again adversely affect loading performance.

A little lubrication to the small spring under the pad usually sorts this problem out.

Again, more details on how to put this right in the Servicing & Repairs section here.

Issue 1 Machines
My own experiences of trickier problems with the Spectrum +2 loading performance mostly tend to centre around tape deck issues with early models with Issue one main boards.

Loading was very much a hit and miss affair with some of these early +2's and no amount of head cleaning, belt changing or tweaking the azimuth really helped.

Machines with Issue 2 boards (and onwards) do seem to be very much better, but I'm not compltely sure whether this is due to a board firmware update, or electronic changes (sush as capacitors) on the issue 2 boards, or adjustments to the cassette units themselves.


Dry Solder Joints
Another problem which I seem to be seeing more and more frequently is a complete failure to load a program and no visible loading border or loading sound.

This can be a faulty play head or incorrect head alignment (azimuth), but is often due to dry solder joints.

If this is the case, the problem is often temporarily cured by sharply banging the spectrum against the table it is sat on (go easy trying this). The loading border then appears and the usual loading sound can be heard.

Also, pressing down with your thumb on the case at the bottom left of the cassette flap during during loading also sometimes temporarily cures the problem as the controller board flexes. However, standing there with your thumb aching for 10 minutes is hardy a cure...

The problem is due to a "dry" solder joint in one or more of the soldering lines on the cassette drive controller board - usually the joints for the red and white wires which connect the read and write heads.

Check the point where the leads from the play head meet the cassette drive controller board, if the solder is a dull grey colour, rather than the shiny metallic colour it should be, this may be a dry joint which needs to be remade.

To do this, add a little flux with a fine children's paint brush to the grey solder blob, then hold the tip of a soldering iron against the poor joint. The solder will melt fairly quickly - take away the iron and the solder should high-flown and set again, usually repairing the joint.
Better still, remove the solder completely, clean up the board and remake the joints for both the red and white leads as shown in the photograph from scratch.


Crackling interference
A static-like, noisy crackle heard through the TV speaker during loading is a similar issue to the dry joint problem described above.

In this case, the dry-joint issue is still there, but the joint hasn't broken down completely. However, it is still usually enough to badly impair loading performance. Again, try pressing down on the case again around the cassette unit whilst loading - the crackle may stop, or more likely get worse.

The cure is the same, BUT, the sound may be coming from other solder joints on the cassette controller board. The "crackle" problem seems to be more of an issue on the +2A boards rather than the +2 boards - possibly because the +2A, has more soldered cable joints.

If you have this problem, re-make the joints shown on the photograph to the right.

Fuller instructions, plus other possible issues and guidance are covered in the Repairs and Servicing section for the Spectrum +2 models.
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