With age the Citizen/NEC Sam Drive drive belt can stretch, break or even turn into a gelatinous mess depending on it’s composition.
A suitable replacement belt is a 71mm diameter flat belt 2.8mm high and 0.6mm thick although there have been reports of mixed reliability.
To replace the belt you must remove the drive from its plastic shell, unscrew the metal shield and the motor bracket to get access to the drive flywheel.
Clean the drive thoroughly to remove dust and fluff from the unit, clean the edges of the flywheel, jockey wheel and the motor spindle with a suitable cleaner such as isopropyl alcohol on a cotton bud - also check the drive head worm gear for fluff build up and re-grease if required.
Take the opportunity to clean the drive heads using isopropyl alcohol and a foam/chamois bud (not cotton), and clean the skid plate under the head assembly.
Fitting the belt can be done as demonstrated here but it can be done without having to remove the drive cage if you have two pairs of tweezers to hold the belt:
With the drive slot facing you:
- As above post cleaning with the top and bottom sheilds removed and the motor assembly popped out.
- Place the new belt around the flywheel.
- Using one pair of tweezers grip the belt about 10mm from the loose end so that it forms a small loop and bring the left side of the belt around the outside and under the silver jockey wheel and to the right hand side towards the right of the post so that they come almost together.
- Bring the loop to the hole below where the motor spindle sits.
- Bring the other pair of tweezers up through the hole and grip the belt loop and release the first pair of tweezers.
- Whilst holding the loop from the bottom, drop the motor back into position, guiding the motors pulley through the loop you are holding, push the loop up as you bring the motor down and it should hook on.
- Screw the motor assembly back down.
With age it has been noted that the surface mount capacitors on the Citizen drives can fail and/or start leaking causing the drive to fail to boot/read/write/format.
As with all capacitor leaks it is essential that the units are replaced and the corrosive electrolyte is removed before it damages the PCB, plus with surface mounts it is often hard to see if they have leaked under the cans but a dull patch or dulled solder points are often an indicator of this.
These can be 3D printed for either a 3.5" standard PC drive or a blanking plate see https://www.thingiverse.com/thing:873336/files