Servicing the Sinclair ZX Spectrum +3 Disk Drive

Servicing the Sinclair ZX Spectrum Disk Drive

Of the Spectrum +3 computers discovered in lofts, or bought from a car boot sale or eBay, 90% will have non-working disk drives.  The drive belt either dries out over time and snaps, or completely self-destructs and turn into a sticky gooey mess all around the drive motor capstan.

Dirty read/write heads, dried out worm drives and missing read/write pins are also common issues.

This paper sets out to guide the complete novice through servicing the +3 disk drive mechanism.  It covers all the most common faults and in most cases will help you get your drive fully working again.

Items and Tools Required

  • Cross head screwdriver
  • Brush to clean out the dust and spiders
  • Long nosed tweezers (or similar)
  • Small pointed pliers (makes life easier)
  • Cleaning buds / swabs / chamois cleaning stick
  • Head cleaning fluid
  • New drive belt (available in shop)
  • Vaseline or other light grease

These are recommendations, other similar tools will do – only the proper belt is essential. Full service kits including cleaning tools, solution and belt are available from the shop.

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 up on the cloth.

Firstly, remove the two small screws on the right of the drive housing on the right hand side of the Spectrum case – don’t lose them, they are difficult to find these days!

Now turn the Spectrum over so it is face down.


There are now five screws to remove from the base.






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 power LED wire which will stop you lifting the top case any further.


Reach inside the case and carefully pull off the LED 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.


Lay the top case face down at the left side of the base – it is not necessary to remove the keyboard ribbon connectors .


The disk drive will now be fully exposed.



Removing the Disk Drive

The disk drive is held in place by a single screw fixing it to the front left mounting post. Remove this and move the earthing wire to one side. It’s possible there may be a screw in the rear mounting post, but they left the factory with just one – Sinclair were tight with their money!

Loosen the metal cable tie to free the power lead, then lift the drive and very carefully disconnect the flat 26 pin ribbon connector and the power supply lead from the rear.

Have patience and take care – if you pull too hard on the ribbon cable you will bend the pins or pull the connector from the cable itself (or both if you really go for it).


 Servicing the Drive

Keeping the disk slot towards you, turn the drive over to give access to the base.   There are various types of drive installed in the Spectrum +3’s but the one shown here is by far the most popular.



Servicing instructions are the same for each drive type, but the screws securing the drive controller board (the drive base) to the drive itself may vary in their position and number. 

Remove the 3 brass screws securing the controller board to the drive noting the type and position (all 3 are different).






On each side of the drive you will find a set of wires – carefully and gently pull these out with the pliers just far enough to be able to get a grip on them with your fingers, then equally gently pull the connectors away from the sockets - DON'T TRY TO PULL THEM AWAY FROM THE SOCKETS WITH THE PLIERS.


Replacing the Belt

With the drive entrance furthest away from you, you should now be able to slide back the controller board towards you slightly (to release the LED from the from drive fascia) and then lift the controller board upwards an inch or so to reveal the drive belt. Don’t turn the drive over with the controller board loose or you will lose the write-protect pin (rare as rocking horse droppings to replace).


What you see now may vary.

If you are lucky the old belt will still be in one piece and you will be able to lift it off the brass capstan of the drive motor and the main pulley with the tweezers.

If you’re not so lucky, the belt will have broken and be wrapped around the capstan as a solid gooey mess.

If so, it is a little more difficult to remove and it will almost certainly leave a sticky black residue on the capstan.

This must be removed as it will cause the new belt to slip during operation and to age very quickly.

The best way to clean off the residue is to apply a few drops of head cleaning solution to a cotton bud (or similar) and rub the capstan, turning it continually with your fingers until all of the residue has been removed.

Don’t skimp on this even though it’s difficult – it is very important. If you have bought a servicing kit from me there will be more than enough head cleaning solution, but you may need more cotton buds depending on how bad the mess is!

When clean, allow the capstan to dry.





To fit the new belt use the tweezers to place the belt over the large pulley first, then finish by stretching it carefully over the capstan.

Ensure that the belt fits snugly and straight over both capstan and pulley - it is essential that it is not twisted.




Now replace the drive controller board, ensuring that the LED fits back into its recess at the front of the drive and fix in place again with the 3 brass screws.

Belt replacement is now complete.



It is essential to use the correct belt – I have had drives sent to me for repair which have 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.



Cleaning the Read/write Head

Turn the drive over again so that the controller board is downwards on the table cover with the front fascia plate nearest to you. You will see a black plastic bar next to the stepper motor worm drive with a felt pad on its tip. Lift this backwards (it is held in place under slight pressure by a small spring) and the read/write head will be exposed. Clean with a swab moistened with head cleaning fluid and then dry, preferably with a chamois stick.


All that needs to be done now is to add a little grease (vaseline is great) to the stepper motor drive worm and the service is complete.

Re-fixing of the drive back and re-assembly of the +3 is the reverse of the removal and disassembly (after giving the inside of the Spectrum a good clean of course).

An important point to remember during re-assembly is to make sure that the ribbon cable is connected to the disk drive the correct way around. The red (or sometimes blue) coloured wire at one edge of the ribbon cable has to be connected to pin 1 of the connector block. Pin 1 is next to the power connector.


 Write-protect Pin


If you find one of these (shown below one of the +3 case screws so you can get a feel for its small size) then you turned the drive over whilst the controller board was loose.
The drive won’t work properly (won’t write) without it and you will need to open her up again to refit it (assuming it hasn't been eaten by a pet or a vacuum cleaner). If you have lost it, then spares are usually available in the on-line shop area of the website.



The pin fits into a small recess just in front of and to the left of the drive belt capstan (viewed from the front of the drive).  See the photograph to the right - it can take some finding.





Re-assembling the Spectrum +3

Remember on all spectrum repairs that when re-assembling you are only screwing into plastic - you are not screwing a shelf to a wall. You only have to over tighten once to strip the thread or crack a pillar - be patient and take care!

Drive Still Won’t Work?

If after following this service guide carefully your drive will still not work, then drop me an email at with the symptoms and I will try to help.

It may need re-alignment of the read/write heads or have a stepper motor problem, both of which need specialist equipment to fix.

However, I have added a section to show how to manually attempt a head alignment repair, but be warned, it can take time and patience.