Servicing the Sinclair ZX Spectrum +2 Cassette Drive
The built-in cassette mechanism of the Spectrum +2 is a fairly robust system which is still very reliable some 25 years on. However, if you purchase or acquire a Spectrum +2 which has not been maintained it is likely that the cassette loading performance will be unreliable.
Fortunately, the problem is usually down to a worn/kinked drive belt, and/or dirty read/write head, and/or incorrect head alignment (azimuth). Often it may be all three!
There were two main models of the Spectrum +2 (plus a few minor revisions).
The first on the scene was the grey model which was the first Spectrum produced by Amstrad. Apart from the added cassette mechanism, it was virtually identical internally to the genuine Sinclair Spectrum+ 128.
The second model released was the black Spectrum +2A. This was a major revision and the main board was completely different and ran on through the +2B and +3 models (the +3 had the disk drive rather than the cassette of course).
However, for the purposes of this paper, the cassette mechanisms were very similar on all models and the servicing is the same. The paper sets out to guide the complete novice through servicing the mechanism on any model of spectrum to improve loading and saving performance. All photographs used are from the black +2A model.
The earlier Spectrum +2 had a smaller belt as part of its drive mechanism and replacement of this is covered at the end of the article.
Items and Tools Required
These are recommendations, other similar tools will do – only the proper belt is essential.
Opening the Spectrum Case
Work on a table or workbench with plenty of space and good lighting. Lay a cloth over the table to protect it (if your partner is watching) and then place the Spectrum face down on the cloth.
Firstly, remove the six screws from the base of Spectrum case – don’t lose them, they are difficult to find these days!
Carefully turn the Spectrum over again holding the top and bottom together to prevent them from falling apart.
Now, gently lift the top from the right hand end until you start to feel some resistance – this will be the cassette power & LED wire which will stop you lifting the top case any further.
Reach inside the case and carefully pull off the lead from its connector on the motherboard - this will free the case top which should now be lifted open fully, in an arc from the right hand end from right to left.
Be careful not to damage the keyboard ribbon which is connected to the motherboard at the left side.
The cassette unit which is housed in the top case will now be fully exposed.
Servicing the Cassette Mechanism
Give the innards a good (but gentle) brush out (holding the nozzle of a vacuum cleaner over the case as you brush helps take the dust and debris away), try and remove all fluff etc from the pulleys, keys and sensors. Light grease was used to lubricate the pulleys, so you may need to wipe them carefully if fluff and dust is stuck to the wheels.
If you turn the large pulley wheel the drive belt passes over, the belt will move – one of the most common problems is a kink in the belt where it has sat stationary over the small capstan motor pulley whilst in storage for many years – you will see this clearly.
Remove the old drive belt with the tweezers.
Now remove the new belt from its pack and open out removing any twists which may have been introduced when it was packaged.
Carefully fit the new belt making sure it is fitted straight and fits snugly with no kinks or twists. If you move the large pulley, the belt should move smoothly.
It is essential to use the correct belt – I have had +2s sent to me for repair which has been fitted with belts which are too small, and some even bodged up with a tight elastic band. Usually it is then too late for repair as the 25 year old drive bearings have been ruined by the excess pressure exerted by the non-standard belt.
The case can now be re-assembled (remember to refit the power/LED lead), again taking care not to damage the keyboard membrane tails.
Replace all of the case screws – be careful not to over tighten, the posts the screws attach to are easy to break, you only get one chance!
Cleaning the Recording Heads
Open the cassette door and press the [Play] key – the play/recording heads will move out and lock.
Add a few drops of alcohol to the chamois cleaning stick and rub both of the heads thoroughly to remove and iron oxide deposits.
Press the [Off] key and leave a minute for the alcohol to dry.
It is possible buy special head cleaning cassettes, but I find these are not particularly good at cleaning off oxide deposits which have sat there on the heads for years. They are fine however for regular maintenance cleaning following a service.
Replacing the smaller belt on the Spectrum +2 grey model
The earlier Spectrum +2 had a smaller belt as part of its drive mechanism. This belt is pretty robust and rarely needs to be changed, but if your +2 has a particularly slack belt, or you suspect that it is slipping, or past its best I can supply a replacement either on its own, or as part off a belt kit (available from the shop).
The belt is a little more tricky to remove - using the tweezers, lift it from the small upper black pulley wheel first.
This peg itself can be a cause of poor loading performance as can catch on the aluminium base of the large pulley wheel causing it to slow down. This problem can usually be heard when loading data from cassettes.
It is possible to lubricate the spring and pin on this peg with careful application of WD40 which usually cures the problem.
Checking the Head Alignment (azimuth)
The azimuth angle can be checked accurately with one of the bespoke kits to do this, but these are hard to find now (keep an eye on the Sales pages in the Sinclair section of the website, I have them occasionally).
A quick method is to adjust the head angle as a tape is starting to load.
You will need the +2 connected up and turned on to do this and a tape which you know to be good.
This method is a little rough and ready, but effective with a bit of practise. Indeed, you may not need to adjust the azimuth, often just cleaning the heads and changing the belt makes all the difference.
Loading Performance Still Poor?
It may need more careful re-alignment of the read/write heads or have a motor problem, both of which need more specialist equipment to fix.