Clean the heads, clean and lightly grease the rails, and find out whether your drive has a belt at all. Some don’t. The A1010 repair at Retro Repairs and Refurbs found a stepper motor and stepper rails, with no belt in sight. Others do have belts, and a perished one is a common reason for a drive that spins and reads nothing.
The symptoms:
- A drive that makes a strange whirring noise and can’t read any disk.
- Read errors on disks that are known to be good.
- A drive that reads but won’t write.
- A grinding noise as the heads hunt for track 0.
Does your drive have a belt?
Open it and look. If a rubber band runs from the motor to the spindle hub, you have one. Steven at Lyonsden found exactly that in a Roctec external drive, and says the original belt perishes after about 30 years. A forum user on Amibay names the Citizen UODC-12A as another drive with a belt. The Mitsumi D357 in the A1010 repair was not belt-driven.
What do you need?
- Isopropyl alcohol (the A1010 repair used 99.9 per cent), cotton buds and a toothbrush.
- A little lithium or white grease.
- Tweezers and a flat screwdriver. Keep metal tools away from the heads.
- A replacement belt, if yours has one, matched by measurement.
- A multimeter, and the Amiga Test Kit disk image for testing.
How do you clean the drive, step by step?
- Remove the drive. Take it out of the machine and open it carefully. Dust inside is a common cause of failure, according to Amibay’s forum users.
- Clean the heads. Cotton buds and isopropyl alcohol, as the A1010 repair did. Use a light touch.
- Clean the rails. Wipe the stepper rails with the same alcohol and buds.
- Grease the moving parts. The A1010 repair used lithium grease on the rails and disk mount. An Amibay user used white grease on the infinite screw. Use very little.
- Check the disk switch. Amibay says the disk-presence switch should show continuity only with a disk inserted.
- Check the power connection. Look for dry or broken solder joints.
- Test it. The A1010 repair used the Amiga Test Kit and ran the read and write tests.
How do you replace a perished belt?
Lyonsden’s Roctec repair is the one worked example I found. It removed six Phillips screws, bent small tabs to take off the plastic fascia, eased the drive out the back and unbolted the motor assembly. It avoided the flat-headed screws. A new flat rubber belt, 71 mm in diameter, 0.6 mm thick and 2.8 mm wide, from Modern Radio, went round the large drive wheel and the small tension wheel.
Belt sizes vary by drive, so measure yours. Check the path by turning the drive wheel by hand and watching the motor armature through the gaps in the motor housing. If the belt runs true, refit the motor and close it up.
What if it still won’t read?
- Grinding. On the Amiga.org forum, a poster called Orange says it is the drive calibrating, going to the last track (79 or 82) and back to 0. He suggests recalibrating with TrackDiskSync from Aminet.
- Heads won’t move. Amibay suggests gently twisting the motor rod. It sometimes restores movement.
- HD disks read as DD. The micro-switch that detects the disk may need cleaning, says an Amibay poster.
- Old capacitors. An Amibay user says through-hole capacitors in these drives are usually 10 or 47 microfarads at 6.3 to 16 volts, and that 25 volts is fine. That is one forum account. Check the board.
- Dead mechanism. The A1010 repair swapped the whole mechanism for a Chinon FB-354 from a donor A500 and had to rewire the activity LED.
Two Amiga.org posters, Argus and K7HTH, blame the even CIA chip when the drive fails after peripherals were connected or removed with the power on, so switch off first.
What should you check afterwards?
- Read and write tests pass.
- The activity LED lights.
- The drive doesn’t grind at power-up.
- The disk-presence switch still works.
