Macintosh HDD Maintenance: Difference between revisions
Removed Category:Hard Drive Maintenance |
Verification drive: removed the +5/+12 V rail table and the 'adjust analog board trimmer R56' instruction - R56 is on the 128K/512K/Plus power-sweep board and regulates +12 V, so that advice pushed +12 V out of spec on the few machines that even have it; added Apple's Hard Drives Service Source procedures (run HD SC Setup first; remove terminator resistors or damage the logic board; torque carrier screws to 8.0 in-lb; 20SC Rev A/B like-for-like matching) |
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* '''Never use WD-40''' – it evaporates and gums up over time. | * '''Never use WD-40''' – it evaporates and gums up over time. | ||
=== Head | === Head actuator and stepper mechanism === | ||
* For stepper motors: apply a tiny amount of oil to the shaft. | * For stepper motors: apply a tiny amount of oil to the shaft. | ||
* For linear voice coil actuators: use dry '''PTFE-based lubricant''' on rails. | * For linear voice coil actuators: use dry '''PTFE-based lubricant''' on rails. | ||
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* Bearings may be beyond repair — consider a '''platter transplant''' into an identical donor chassis (with care to preserve alignment). | * Bearings may be beyond repair — consider a '''platter transplant''' into an identical donor chassis (with care to preserve alignment). | ||
=== ROM or | === ROM or controller failures === | ||
* Drive spins but is not | * Drive spins but is not recognised? Run '''HD SC Setup''' before suspecting hardware — a stale driver presents identically.<ref name="hdss">Apple Computer, Inc., ''Hard Drives Service Source'' (SCSI drives and IDE drives): Troubleshooting → HD SC Setup; Upgrades → "Drives in Quadra 900/950" and "Identifying 20SC Rev A & B"; Additional Procedures → Carrier Removal, Torque Sequence and Modifying 5.25-Inch Drives. Hosted on this wiki as [[:File:Macintosh Disk Drive and UniDisk 3.5.pdf]] — the file name on this wiki is wrong; the document inside is the Hard Drives volume.</ref> | ||
* Then check SCSI ID conflicts and termination, which present identically again. | |||
* Only then suspect the drive's own logic board. Replace with an identical board from a working donor; on drives of this era the board carries drive-specific adaptive data, so a board from a different revision may not work even if it fits. | |||
== Component Repair & Replacement == | == Component Repair & Replacement == | ||
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* Install '''Kapton, silicone, or precision-cut rubber tubing'''. | * Install '''Kapton, silicone, or precision-cut rubber tubing'''. | ||
== Voltage and | == Voltage and power supply checks == | ||
A drive that spins up and then drops out, or that will not spin at all while the machine is | |||
otherwise healthy, is often a supply problem rather than a drive problem — the +12 V rail | |||
sags under the spin-up surge. | |||
'''Two things that used to be on this page have been removed, and it matters that they are | |||
not repeated elsewhere.''' | |||
'''The rail table.''' "+5 V 4.85–5.15 V / +12 V 11.9–12.7 V" is Apple's '''Macintosh Plus''' | |||
adjustment procedure. It is genuine ''there'': the ''Macintosh Plus Service Source'' has you | |||
* | fit voltage test cable '''077-0135''' to the external floppy port and read 4.85–5.15 V on the | ||
red lead and '''11.90–12.75 V''' on the orange one — note 12.75, not 12.7. It is not a | |||
general Macintosh specification, and Apple publishes no rail tolerance at all for the SE, | |||
SE/30, Classic, Classic II, Color Classic, the Quadra family, the Power Macintosh family or | |||
any other machine checked so far. | |||
'''The R56 adjustment.''' R56 is the trimmer named in that Macintosh Plus procedure. It lives | |||
on the '''128K/512K/Plus power/sweep board''' and it regulates '''+12 V, not +5 V'''. Telling | |||
a reader to "adjust R56" to fix a hard-drive supply problem is wrong twice over: on most | |||
machines the component does not exist, and on the machines where it does, turning it to chase | |||
a +5 V reading pushes '''+12 V''' out of specification — straight into the drive's spindle | |||
motor supply. | |||
What to do instead: | |||
* Measure at the drive's own power connector, with the drive connected and the machine booted, not at the supply with no load. | |||
* Compare '''+5 V''' against the specification of the 5 V logic it feeds — 5 V ±5 per cent, so '''4.75 V to 5.25 V'''. | |||
* Watch the rails on an oscilloscope while the drive spins up. A rail that dips and recovers points at tired output capacitors in the supply; steady DC with visible ripple points the same way. | |||
* If the supply is out, recap or replace it. There is no adjustment to make on these machines. | |||
== Apple's own procedures for replacing a drive == | |||
Apple's ''Hard Drives Service Source'' is short but contains several things that will damage | |||
hardware if you get them wrong.<ref name="hdss" /> | |||
=== Run HD SC Setup first === | |||
'''Before you replace any drive hardware, run HD SC Setup to update the driver on the | |||
drive.''' It is Apple's first step for a misbehaving drive, and it works with both SCSI and | |||
IDE drives. A drive that will not mount because of a stale or corrupt driver looks exactly | |||
like a dying drive.<ref name="hdss" /> | |||
=== Remove the terminator resistors === | |||
'''Apple's caution is explicit: "failure to remove the terminator resistors can damage the | |||
logic board."''' Service replacement drives shipped terminated, and the terminators have to | |||
come off before the drive goes into a machine that terminates elsewhere.<ref name="hdss" /> | |||
* On the 160 MB drive, pull up on the tab to lift the resistor pack out. | |||
* On the 230 MB drive, use needle-nose pliers and pull the resistors straight up. | |||
* On 5.25-inch external replacements, disconnect the resistors from the component side, again pulling straight up. | |||
Watch the orientation of the SCSI select cable as well: Apple specifies tab-up on the 160 MB | |||
and 230 MB drives and tab '''down''' on the 400 MB drive.<ref name="hdss" /> | |||
=== Torque the carrier screws === | |||
'''Torque the four carrier screws to 8.0 inch-pounds''', in the sequence shown in Apple's | |||
figure. Apple warns that failing to torque the drive to its carrier properly "could damage | |||
the drive"; its own torque driver is preset to 8 in-lb, and the sequence is the same for | |||
every drive and carrier type.<ref name="hdss" /> Over-tightening distorts the HDA casting and can put the | |||
spindle out of true — this is a real failure mode, not a formality. | |||
=== Revision matching === | |||
The '''Hard Drive 20SC 3.5-inch Revision A (661-0373) and Revision B (661-0612)''' must be | |||
replaced like-for-like. Apple's identification is physical: Revision A drives ship in an | |||
internal carrier '''component side up''', Revision B '''component side down'''.<ref name="hdss" /> | |||
== Additional Resources == | == Additional Resources == | ||
* [[Hard Drive Maintenance and Repair]] — the general, non-Macintosh-specific guide | |||
* [[Macintosh SE/30 Troubleshooting]] | * [[Macintosh SE/30 Troubleshooting]] | ||
* [[Macintosh SE General Maintenance]] | * [[Macintosh SE General Maintenance]] | ||
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* [[:Category:Apple Service Source|Apple Service Source]] | * [[:Category:Apple Service Source|Apple Service Source]] | ||
== References == | |||
<references /> | |||
{{Navbox-AppleVintage|state=collapsed}} | |||
[[Category:Apple Vintage Computers]] | [[Category:Apple Vintage Computers]] | ||
[[Category:Apple Maintenance Guides]] | [[Category:Apple Maintenance Guides]] | ||