Servicing the Amstrad CPC6128 Disk Drive

 

 The built-in disk drive of the Amstrad CPC6128 is a fairly robust (if non-standard) 3” system which is still very reliable some 25 years on. However, if you purchase or acquire a 6128 which has not been maintained it is very unlikely that the drive will function.

Fortunately, the problem is usually down to a perished drive belt, and/or dirty read/write head, and/or dried out lubrication of the worm drive which positions the head. More than likely it will be all three!

 

This article sets out to guide the complete novice through servicing the drive and getting it back on its feet.

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
  • Head cleaning fluid
  • New drive Belt
  • 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 CPC6128 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 CPC 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 CPC case – don’t lose them, they are difficult to find these days!  

Now turn the CPC over so it is face down.  

  

 

There are now six screws to remove from the base.  On some models there is a 7th screw (marked) – if this screw is present, it is longer than the others – make sure it goes back in the same hole.  

Carefully turn the CPC over again holding the top and bottom together to prevent them from falling apart. 

 

  

Now, gently lift the top with both hands for about an inch, then carefully turn the top over from right to left and lay the top down on its keys at the side of the base. 


Take care not to damage the keyboard ribbon which is connected to the motherboard at the left side.

 

The disk drive will now be fully exposed at the right hand end of the base case.

 

 

 

Removing the Disk Drive

The disk drive is held in place by two screws fixing it to two mounting posts.  Remove these and move the earthing wire attached to the nearest post to one side. 

 

 

   

 

 


Loosen the ribbon cable from the plastic cable tie hook, 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

There are various types of drive installed in the CPC6128 but the one shown in this guide is one of the more common.  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.  Also, some drives make use of a write protect pin (the drive in this guide does not) which has caused many people many problems over the years – more of that later!

 

Keeping the disk slot towards you, turn the drive over to give access to the base.

 Remove the two brass screws (take care not to lose any washers) securing the controller board to the drive noting the type and position (they can be different).


 


At the power and ribbon connector end of the drive you will find two or three sets of wires (on other drive models, these may be at either side of the drive) – carefully and gently pull these with your fingers (you may need to ease them out with the pliers first to let you get hold of them properly), so that the connectors are pulled out away from their sockets.
  

 

This stage is not essential, but it does give you a little more room to lift the controller card to allow space to remove the drive belt. 

 


 

 

Replacing the Belt

With the drive entrance furthest away from you, you should now be able to lift and 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 if one is fitted.


What you see now may vary – the drive capstan (brass pulley wheel) may be on the left or the right.

 

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. 

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

This must be removed as it will cause the new belt to slip during operation and also 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 the entire residue has been removed.  You may need to carefully scrape off any stubborn bits of belt with a small flat blade screwdriver.   

Don’t skimp on this cleaning operation even though it’s difficult – it is very important. 

 

When clean, allow the capstan to dry for a minute or two..

 

 

Fitting the New Belt

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 over both capstan and pulley and that 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 brass screws.

Belt replacement is now complete.


Important
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 with the front fascia plate nearest to you.

 

You will see a black plastic bar next to the stepper motor drive worm 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 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-Assembly

Re-fixing of the drive back into and re-assembly of the CPC6128 is the reverse of the removal and disassembly (after giving the inside of the 6128 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 tiny pins 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.

 

 

 

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).

Most drives used in 6128’s detect a write protected disk by a light beam and sensor, and don’t make use of these mechanical pins – but you never know what you will find until you open her up – be careful and watch out for the pin!

 

 

 

 

 

Drive Still Won’t Work?

If after following this service guide carefully your  drive will still not work, then drop me an email 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.