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Apple Hard Disk 20 Troubleshooting Guide

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HD20 Control Board
Apple Hard Disk 20 controller board

The Apple Hard Disk 20 (HD20) is Apple's 1985 external hard disk for the Macintosh floppy port. Apple documented its faults in the Hard Disk 20 Technical Procedures and in a set of problem-and-cure articles in its Tech Info Library, and the tables here are arranged by symptom from those sources. Apple's full troubleshooting flowchart, the switch-on order and the take-apart procedure are on Apple Hard Disk 20 Maintenance.

Warning: the HD20 has a mains power supply inside the case. Unplug it before removing the cover.

Before you start

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Apple's rules for the HD20:[1]

  • Back up anything readable as soon as the drive comes ready. Do not reinitialise the disk until every recovery step has been tried, because initialising erases everything on it.
  • If the drive never comes ready, the data on it cannot be recovered.
  • Test the HD20 on a known-good Macintosh first, then on the owner's Macintosh.
  • Switch the HD20 on before the Macintosh, and switch it off only when the green light is steady.
  • A Macintosh 128K or 512K needs the Hard Disk 20 Startup diskette in the internal drive. A Macintosh Plus does not.

Check also that the Macintosh supports the drive at all. The SE/30, IIcx, IIsi, LC and the II-family machines without an external floppy port have no HD20 code in ROM, and no Apple II can use an HD20. The compatibility table on the main page lists each model.[2]

Power-up and the ready light

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The HD20 should "whir and chirp" when switched on, and the green light on the front should be on and steady within 15 seconds. The light flashes while the heads move.[1] Apple's specification gives a start-up time of 15 seconds and a spin-down time of 25 seconds.[3]

Power-up faults
Symptom Probable cause Action
Drive silent, no light Power supply or mains lead Check the mains lead and outlet. The supply accepts 85-270 V without a selector switch.[4] Apple's order is to replace the power supply, then the fan.[1]
Drive not heard coming up to speed Power supply or fan With the cover off, check that the fan turns at power-up. Replace the power supply, then the fan.[1]
Drive runs but the light is not on and steady after 60 seconds HDA, controller board or power supply Apple's notes say this usually means the HDA is bad. Apple's order of replacement is controller board, HDA, then power supply.[1]

Macintosh does not see the drive

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Connection faults
Symptom Probable cause Action
No HD20 icon on the desktop Macintosh switched on before the HD20 Switch both off, then switch on the HD20 first and the Macintosh second. Apple's owner's guide gives this as the usual cause.[5]
No HD20 icon, drive ready, switch-on order correct External drive port on the Macintosh Connect a known-good external floppy drive and run the external drive port test on the MacTest diskette. If it fails, Apple's cure is the Macintosh logic board.[1]
Works on one Macintosh, not another Model without HD20 support in ROM See the compatibility check above. On a 128K or 512K, start from the Hard Disk 20 Startup diskette.[1][2]
Intermittent errors with an extension cable Cable too long or unshielded Apple rates 30 inches (76 cm) of shielded cable as safe; longer cables add capacitance and voltage drop, and flat or unshielded cables pick up interference.[6]
Drives chained behind the HD20 not seen, or intermittent Cables, or the expansion port on the HD20's controller board Check the cables. Connect each chained drive directly to the Macintosh. If they all work that way, the expansion port connector on the first HD20's controller board is the likely fault, and Apple's cure is a new controller board.[1]

Initialising and formatting

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Initialisation faults
Symptom Probable cause Action
"Init Failed" on a known-good Macintosh Controller board Replace the controller board, then the HDA with its analogue board.[7]
Will not initialise, applications fail to launch, or files do not copy to the HD20 HAL chip in place of the PAL on the controller board Check the serial number. On units from F619xxx, look at board location C3, which is silkscreened "PAL is 16R6". If a HAL chip is fitted there, Apple's cure was to replace the controller board.[8]
Unsure whether the disk is HFS Formatted under an old system Erase the disk from the Special menu. In the disk window, an HFS volume shows a one-pixel dot at the left of the two thin lines near the top.[9]

Startup problems

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A corrupted Finder on the HD20 shows four symptoms when the Macintosh tries to start from it: the startup does not complete, the diskette is ejected, the Macintosh and HD20 lock up, and no HD20 icon appears. Apple's cures, one at a time and in this order, are:[1]

  1. Run Disk First Aid from the Hard Disk Drive Diagnostic diskette with "Repair Automatically" selected. Switch on the Macintosh first, then the HD20, for this step.
  2. Start from the Hard Disk 20 Startup diskette, holding the mouse button until the desktop appears, and drag the diskette's System and Finder to the HD20. A later Apple article asks for Finder 5.0 or later on the Startup diskette before copying it across, and for the System and Finder to be inside the HD20's System Folder.[10]
  3. Rebuild the desktop: hold Command and Option throughout the start-up from the Startup diskette and answer OK.
  4. As a last resort, initialise the HD20: hold Command, Option and Tab throughout the start-up and answer OK. This erases the disk.

The two Apple documents differ on the desktop rebuild. The Technical Procedures use Command-Option.[1] The Tech Info Library article uses Command-Option-Tab, which first offers to initialise the disk; it tells the reader to click Cancel there and then OK to rebuild the desktop.[10] Holding only Command and Option avoids the erase prompt.

These steps cure software faults. If the symptoms return, work through the hardware checks above.[1]

System software

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System software problems
Symptom Probable cause Action
"File System not found on System Tools" when running Installer on a Macintosh 512K Installer and HFS on the 512K Drag a copy of the System Folder from the Tools disk, or move the System file out of the System Folder while running Installer 2.0. Apple says the Macintosh Plus does not have the problem.[11]
Macintosh 512Ke hangs at start-up with a blank dialog box after an update to System 6.0.3 System 6.0.3 on the 512Ke Start from a System 6.0.1 disk. Apple recommends System 4.1 with Finder 5.5 for the 512Ke.[12]
Odd behaviour with several System Folders on the HD20 More than one System file Apple did not recommend multiple System files on the HD20.[13] Keep one, in the System Folder.
Applications launch slowly, slow start-up Fragmented files after the desktop has been rebuilt, or a nearly full disk With Finder 4.1 or later, copy every file to a second, freshly formatted drive, erase the HD20, and copy the files back.[14]

Diagnostics

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Apple's Hard Disk Drive Diagnostic runs a self-test, an ID test, a random single-block test, a random multi-block read test and a scan of the drive. It offers a 15-minute test and an overnight test of 20 iterations.[1]

  • Version 4.0 of the diagnostic always fails an HD20 tested on a Macintosh SE, even a good one. Test the HD20 on a Macintosh Plus. An HD20 formatted on an SE can still fail on the Plus; format it on the Plus and test again.[15]
  • Hard Disk 20 Test, on the Startup disk, takes about 15 minutes and tests hardware only. Apple's owner's guide suggests running it every month or so.[5]
  • "HD 20 Test" version 1.1 has two hidden functions. Press Command-D at the main dialog for a detailed window with a "Dstrct" option, which writes zeros to every block. Press Command-E for a 24-hour extended test.[16] The Dstrct option destroys all data on the drive.

Getting data off an HD20

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To move files to a Macintosh that cannot use the HD20, such as an SE/30, Apple's procedure is to connect the HD20 and a formatted SCSI drive to a Macintosh Plus or SE, start from a System Tools disk with both drives switched on, check there is only one System file on the HD20, copy everything to the SCSI drive, and then move the SCSI drive to the other Macintosh.[17] Apple also supplied an unsupported Init for reading an HD20 on the SE/30, and warned that writing to the HD20 with it could lose or corrupt data.[17]

Modules and repair

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Apple serviced the HD20 as three exchange modules: the controller board, the power supply, and the hard disk assembly (HDA), which is the hard disk and its analogue board. Apple required the HDA to go back for exchange in Apple-approved packaging.[1] The cable between the controller board and the HDA is not a standard ribbon cable; replace it only with Apple's cable (590-0336), because the wrong cable can damage the drive or the controller board.[1][18]

Apple's documentation stops at module level and gives no schematic or component values for the controller board or power supply.[1] For general drive-side work, see Hard Drive Maintenance and Repair; for failed electrolytic capacitors in the power supply, see Capacitor Failure Symptoms.

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References

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  1. ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 Apple Computer, Hard Disk 20 Technical Procedures (from Apple Service Technical Procedures, Volume Six), hosted as File:Apple Hard Disk 20 Technical Procedures.pdf. Section 1, Basics, pp. 1.2-1.3 (switch-on and switch-off order, the green light, the Startup diskette, reinitialising); Section 2, p. 2.2 (Hard Disk Drive Diagnostic); Section 3, Troubleshooting, p. 3.2 (things to remember, three exchange modules), p. 3.3 (no Startup diskette with the Macintosh Plus; HDA cable caution), p. 3.4 (flowchart), p. 3.5 (flowchart notes), pp. 3.6-3.8 (startup problems), p. 3.9 (daisy-chaining problems).
  2. ↑ 2.0 2.1 Apple Computer, "Apple HD-20 (Non-SCSI): Which Macintosh Computers Support It", Tech Info Library article 4423, revised 4 March 1991, in the archive.org collection Apple's Technical Information Library Articles, https://archive.org/details/APPLE_TIL_ARTICLES, file TIL00001_to_TIL60496.zip.
  3. ↑ Apple Computer, "Hard Disk 20: Specification (Discontinued)", Tech Info Library article 1306, revised 14 September 1993, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip. Start-up 15 s, spin-down 25 s; line voltage 85-270 V AC, 47-64 Hz; 30 W.
  4. ↑ Apple Computer, "HD20: Line voltage", Tech Info Library article 1611, revised 9 January 1986, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  5. ↑ 5.0 5.1 Apple Computer, Macintosh Hard Disk 20 (owner's guide, 1985), Chapter 3, pp. 39-41 (PDF pp. 46-48), hosted as File:Apple Hard Disk 20 Owners Guide 1985.pdf and described at Apple Hard Disk 20 Owner's Guide. Source for the switch-on order as the cause of a missing icon, replacing a damaged System file from the Startup disk, and Hard Disk 20 Test.
  6. ↑ Apple Computer, "Hard Disk 20: Cable length limit with Macintosh", Tech Info Library article 1957, revised 12 October 1987, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  7. ↑ Apple Computer, "Hard Disk 20 P/C: First Time Start-Up = Init Failed", Tech Info Library article 1604, revised 30 January 1992, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  8. ↑ Apple Computer, "Hard Disk 20: Failure To Launch Application Or Format", Tech Info Library article 1962, revised 17 January 1992, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  9. ↑ Apple Computer, "Macintosh Hard Disk 20: How To Verify HFS Formatting", Tech Info Library article 8757, revised 26 September 1991, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  10. ↑ 10.0 10.1 Apple Computer, "Hard Disk 20: Boot From HD20 Locks Up HD20 and Macintosh", Tech Info Library article 1685, revised 10 November 1988, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip. Source for the Finder revision check (5.0 or later), the System Folder check, and the Command-Option-Tab sequence with Cancel at the initialise prompt.
  11. ↑ Apple Computer, "Macintosh 512K: Problems installing new drivers on the HD20", Tech Info Library article 1770, revised 18 September 1987, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  12. ↑ Apple Computer, "System 6.0.3: Incompatible with Macintosh 512Ke and HD20", Tech Info Library article 4437, revised 22 September 1989, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  13. ↑ Apple Computer, "Hard Disk 20: No Multiple System Folders", Tech Info Library article 676, revised 12 October 1987, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  14. ↑ Apple Computer, "Hard Disk 20: Applications Launch Slowly", Tech Info Library article 2017, revised 10 November 1988, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  15. ↑ Apple Computer, "Hard Disk 20: Hard Drive Diagnostic 4.0 Problem/Cure", Tech Info Library article 3100, revised 22 July 1988, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  16. ↑ Apple Computer, "HD-20: Erasing Information to Government Specs", Tech Info Library article 2225, revised 27 August 1992, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
  17. ↑ 17.0 17.1 Apple Computer, "Old HD-20 and New Macintosh SE/30", Tech Info Library article 6182, revised 1 November 1990, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip. Source for the transfer procedure and the warning not to write to the HD20 with Apple's unsupported read Init on the SE/30.
  18. ↑ Apple Computer, Hard Disk 20 Service Source, Take Apart, Hard Drive, hosted as File:Hard disk 20.pdf and described at Apple Hard Disk 20 Service Source.


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