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[[File:Floppy Disk Drives 8 5 3.jpg|thumb|Floppy disk drives]]
= General Floppy Drive Repair Guide =
Floppy disk drives were the main removable storage for vintage computers from the 1970s to the early 2000s. This page covers the faults that are common across manufacturers and the procedures that apply to most 5.25-inch and 3.5-inch mechanisms. For drive-specific figures — spindle speed tolerances, alignment limits, belt part numbers — go to the machine's own service manual; the [[Tandon TM100-2]] page is a worked example with the manufacturer's real numbers.
[[File:Floppy Disk Drives 8 5 3.jpg|thumb|Floppy Disk Drives]]
Floppy disk drives were an essential storage medium in vintage computing systems from the 1970s through the early 2000s. These drives came in several formats:


* '''5.25" Drives''' – Found in early IBM PCs, Commodore, Apple II, Atari, and Tandy computers.
Formats you are likely to meet:
* '''3.5" Double Density (DD, 720KB/800KB)''' – Used in IBM PCs, Macintosh, Atari ST, and Amiga computers.
* '''3.5" High Density (HD, 1.44MB)''' – Common in later IBM PC compatibles, Macintosh, and Amiga systems.


Over time, these drives suffer from '''dust buildup, hardened lubricants, mechanical misalignment, and aging electronics'''. This guide will walk you through diagnosing, cleaning, and repairing these drives for long-term use.
* '''5.25-inch, 48 TPI, 40 tracks''' — IBM PC, Commodore, Apple II, Atari, Tandy. 250 KB unformatted per side; formatted as 160/180 KB single-sided or 320/360 KB double-sided on the PC.
* '''5.25-inch, 96 TPI, 80 tracks''' — the 1.2 MB "HD" drives of the PC/AT era.
* '''3.5-inch double density''' — 720 KB on the PC, 800 KB on the Macintosh and Amiga with different low-level formats.
* '''3.5-inch high density''' — 1.44 MB.


== Disassembly and Cleaning ==
'''The single most useful thing to understand before starting:''' the vast majority of "dead" drives are not electrically dead. They are drives whose rail lubricant has hardened, whose heads are caked in oxide from a perished diskette, or whose belt has perished — and whose owner is testing them with the diskette that caused the problem.


=== Preparing for Maintenance ===
== Before you start ==
Before servicing any floppy drive:
* Power off and unplug the computer or drive enclosure.
* Discharge static electricity using an '''anti-static wrist strap'''.
* Work on a clean, well-lit, static-safe surface.


To remove the drive:
* Power off and unplug the machine or enclosure.
* Unscrew the outer case or bracket holding the drive.
* Wear an anti-static wrist strap with a current-limiting earth lead when handling the logic board — see [[Recommended Tools]].
* Carefully disconnect the '''ribbon data cable''' and '''power cable'''.
* Note the ribbon cable orientation and the terminator/jumper configuration before removing anything.
* Keep at least one '''known-good''' diskette that you have not used in the suspect drive. Testing a cleaned drive with the disk that fouled it is the classic trap.<ref name="mzd">"Tandon TM100-2 in IBM 5150/5155/5160 — Known Problems/Issues", minuszerodegrees.net. Cited for: silicone-based lubricant (grease or spray) on the head carriage rails; the use of isopropyl alcohol on a cotton tip for heavy oxide build-up, against the manufacturer's caution, and the fact that head cleaning diskettes are themselves abrasive; the trap of re-testing with the diskette that fouled the heads; media requirements (double-sided, double-density, soft-sectored for the IBM controller) and the problem of double-density disks written in a high-density drive; spindle speed 295.5–304.5 RPM, the R4 speed adjustment and the 50 Hz / 60 Hz strobe rings on the spindle flywheel; loose spindle flywheel screw as a cause of speed error; C36 and C43 (4.7 µF / 16 V tantalum) as the first suspects when a drive overloads the host power supply; and Chuck(G)'s observation via VCFed that many apparent alignment faults are a dirty track 0 sensor. A strong community reference for IBM PC hardware, cited here as a secondary source.</ref>


=== Cleaning the Drive Mechanism ===
== Cleaning ==
To clean your drive:
* Use '''compressed air''' to remove dust.
* Clean metal rails and gears with '''isopropyl alcohol (90% or higher)'''.
* Remove any old grease and apply a small amount of '''plastic-safe synthetic grease'''.
* Clean read/write heads with a '''cotton swab''' lightly soaked in isopropyl alcohol.
* For 5.25" drives, inspect the '''pressure pad''' opposite the head and replace if worn.


== Alignment and Calibration ==
=== The mechanism ===


=== Track 0 Sensor Alignment ===
* Blow out dust with a bulb blower or filtered compressed air.
If the drive constantly clicks or cannot locate disk sectors:
* Clean hardened lubricant off the head carriage rails with isopropyl alcohol and a lint-free cloth.
* Locate the track zero sensor (optical or mechanical).
* Inspect the belt; a belt that is glazed, slack or leaves black dust is finished.
* Loosen its mounting screws and make small adjustments while testing a known-good disk.
* On 5.25-inch single-sided drives, check the '''pressure pad''' opposite the head. A hardened, compressed or missing pad gives weak, intermittent reads.
* Tighten after proper alignment is restored.
[[File:Panasonic JU-268A016C-8166.jpg|thumb|Floppy Drive (Open) Read/Write Head]]


=== Read/Write Head Alignment ===
=== The heads ===
If the drive can read its own formatted disks but not others:
* Loosen the screws on the '''stepper motor'''.
* Rotate slightly to adjust alignment.
* Test using a disk formatted on a different computer for compatibility.


*Note: Proper alignment often requires a factory test disk or alignment software.
{{Warning|'''Do not clean floppy drive heads by hand as a first resort.''' Tandon's service manual for the TM100 series states: '''"Do not use cotton swabs, solvents, or otherwise clean the head(s) by hand. Damage to the head(s) may result."''' Its position is that good media normally keeps the heads clean, and that where contamination is severe a '''cleaning diskette''' should be used according to its manufacturer's instructions.<ref name="tandon">''Tandon TM100-1 / TM100-2 48 TPI Operating and Service Manuals'', Tandon Corporation, manual part number 179022-001 Rev. B, July 1983 — hosted on this wiki as [[:File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf]]. Section 6.1 and 6.2 (symptom diagnostic techniques and soft errors, including the caution against cleaning heads by hand and the soft-error checklist), section 5 (maintenance checks and adjustments, alignment tolerances, the Dysan 224/2A certified alignment diskette and the one-hour temperature stabilisation requirement), Table 2-1 (300 RPM ± 1.5 %, 250 kbit/s, seek and settling times) and Appendix A (spare parts list). Tandon's instructions are specific to its own drives but the head-handling caution reflects general practice of the period.</ref>}}


== Common Floppy Drive Failures ==
In practice:


=== Drive Cannot Read Disks ===
# '''Start with a cleaning diskette.''' This is the manufacturer-sanctioned route. Cleaning diskettes are mildly abrasive, so use them when there is a reason to, not on a schedule.<ref name="mzd" />
Possible causes:
# '''Heavy oxide contamination''' — where a perished diskette has wiped a thick brown layer onto the heads — is beyond what a cleaning diskette will shift in one pass. Restorers do use isopropyl alcohol on a cotton tip here, very carefully, and report that clearing a thick layer can take minutes of patient work.<ref name="mzd" /> That is a considered departure from manufacturer guidance on a drive that is otherwise unusable. It is recorded so you know what you are trading; it is not this page's default advice.
* '''Dirty or oxidized heads'''
# '''Never use a dry swab, abrasive, or a solvent other than isopropyl alcohol''' near the head.
* '''Failed or misaligned stepper motor'''
# '''Throw the offending diskette away.''' A disk that sheds oxide will foul the heads again within seconds.<ref name="mzd" />
* '''Failed spindle motor'''
* '''Worn or demagnetized heads'''
* '''Defective floppy disks'''


Fix:
=== Connectors ===
* Clean heads thoroughly.
* Test motors with a multimeter.
* Replace worn heads or motor with parts from a donor drive.


=== Eject Mechanism Issues ===
Oxidised edge connectors and ribbon headers cause faults that look like drive faults. Clean the drive's edge connector, the controller card's edge connector and the ISA or expansion slot. A dielectric connector grease such as NyoGel 760G is designed for exactly this job — protecting contacts against fretting and corrosion, with a dielectric breakdown of 11.2 kV and a service range of −40 to 135 °C.<ref name="nye">''NyoGel® 760G — The Leading Connector Grease'', Nye Lubricants (Fuchs). Cited for the product being a PAO/silica dielectric '''connector''' grease intended for electrical contacts — preventing fretting wear and corrosion and reducing mating force — with typical properties of −40 to 135 °C service range, kinematic viscosity 400 cSt at 40 °C and dielectric breakdown voltage 11.2 kV. It is '''not''' marketed as a mechanism, rail or gear lubricant.</ref> It is '''not''' a mechanism lubricant, despite being frequently recommended as one.
Symptoms:
* Drive won't eject the disk.
* Constant clicking or eject cycling.


Fix:
== Lubrication ==
* Lubricate mechanical eject gears.
* Replace worn or cracked gears (common on Sony drives).
* Clean eject switch contacts or sensors.


=== Mechanical Wear or “Slipping” ===
'''What to use.''' For the head carriage rails, a '''silicone''' grease. That is the restoration-community consensus for the Tandon full-height drives and applies equally to most similar mechanisms.<ref name="mzd" /> Apply a thin film; the carriage should slide with no more resistance than the stepper's own detent.
Symptoms:
* Drive fails intermittently.
* Disk reads fail only under certain angles or temperatures.


Fix:
'''What not to use, and why:'''
* Check head spring tension.
* Ensure rails are lubricated and carriage moves smoothly.
* Verify correct operation of optical or mechanical limit switches.


=== Stepper Motor Failures ===
* '''White lithium grease''' — widely repeated as the right choice for drive rails, but no drive manufacturer document consulted for this page specifies it.
Stepper motors move the head between disk tracks. Symptoms of failure:
* '''NyoGel 760G and other connector greases''' — designed for electrical contacts, not sliding mechanisms.<ref name="nye" />
* Head doesn’t move.
* '''WD-40''' — a water-displacing penetrant, not a lubricant. It thins existing grease, migrates to places you did not intend, and leaves a sticky residue as the carrier evaporates.
* Drive seeks incorrectly or makes erratic noises.
* '''Oil on a stepper motor shaft''' — the shaft bearings are not a user-serviceable part and oil migrates onto the lead screw and into the optics.


Fix:
'''No service interval.''' There is no manufacturer figure for re-greasing a floppy drive, and the honest answer is that a drive that is in regular use and moving freely does not need it. Re-lubricate when the carriage is stiff, when you have cleaned old lubricant off, or when the drive has come out of long storage — not on a calendar.
* Apply a drop of lightweight machine oil to the motor shaft.
* Measure coil resistance with a multimeter.
* Replace the motor if resistance is outside specification.


== Lubrication Tips ==
== Alignment and adjustment ==


For smooth operation:
{{Warning|'''Radial head alignment cannot be done by trial and error, and attempting it makes a drive worse far more often than it makes it better.''' It requires a certified alignment diskette — one that cannot be copied — and an oscilloscope. Tandon specifies the '''Dysan 224/2A''' or equivalent for its 48 TPI drives, and requires both diskette and drive to stabilise at room temperature for '''one hour''' before any check.<ref name="tandon" />}}
* Lubricate rails, gears, and eject cams with '''Nyogel 760G''' or similar synthetic grease.
* Avoid petroleum-based products like '''WD-40''', which break down plastics and gunk up over time.
* Reapply grease every 2–3 years depending on use.


== Troubleshooting Specific Drive Types ==
'''Rule out everything else first.''' Alignment is the diagnosis of last resort. True alignment drift is indicated when '''both''' of these are true:
[[File:Sony MPF920 F 1.44 MB 3.5" Floppy Drive (2).jpg|thumb|Sony 3.5" Floppy Drive]]


=== 3.5" Drives (Sony, Alps, Mitsubishi, Chinon) ===
# Disks formatted in the drive read back correctly '''in that same drive''', and
* Common in Macintosh, Amiga, and IBM PC systems.
# The drive cannot read good disks formatted on a known-good, correctly aligned drive.<ref name="mzd" />
* Check for sticky eject mechanisms and cracked gears.
* Sony drives often suffer from hardened grease and eject gear failure.
[[File:BASF 6108 - 5 ¼” Floppy Disk Drive.jpg|thumb|BASF 5.25" Floppy Drive]]


=== 5.25" Drives (TEAC, Shugart, Epson, Panasonic) ===
Even then, the more likely causes are:
* Used in early IBM PC, Apple II, Commodore, and Tandy systems.
* Pressure pads can wear out and cause low contact force.
* Head alignment is more sensitive and may require factory alignment disks.


== Preventative Maintenance and Storage ==
* '''A dirty track 0 sensor.''' Chuck(G), quoted on minuszerodegrees, notes that many apparent alignment faults on these drives turn out to be a dirty track 0 sensor.<ref name="mzd" /> Clean the optics before touching anything adjustable.
* '''Rail drag''' — the carriage not reaching the commanded cylinder.
* '''Spindle speed out of tolerance.'''
* '''The media.''' A double-density disk written or formatted in a high-density 1.2 MB drive does not meet the double-density standard and often cannot be read in a DD drive.<ref name="mzd" />


* Periodically power up drives to keep lubricants distributed.
=== Spindle speed ===
* Store drives in '''dry, dust-free environments'''.
* Keep test disks on hand for alignment and compatibility testing.
* Avoid storing disks in the drive to prevent spring fatigue.


== Additional Resources ==
The one adjustment that is safe to make. Tandon's specification for the TM100 series is '''300 RPM ± 1.5 %''' — 295.5 to 304.5 RPM — adjusted at R4 on the servo board.<ref name="tandon" /><ref name="mzd" /> Most 300 RPM drives of the period share both the figure and the adjustment method. Three ways to measure:<ref name="mzd" />


* [[Capacitor Replacement Guides]]
# The '''strobe rings''' moulded or printed on the spindle flywheel, one marked 50 Hz and one 60 Hz. Use the ring matching your mains frequency, under strong mains-powered fluorescent light. The pattern should stand still.
* [[CRT Discharge Procedure]]
# '''ImageDisk's Test RPM''' command, or an equivalent utility.
* [[Macintosh HDD Maintenance]]
# A digital oscilloscope with a frequency readout on the tachometer output of the speed-control IC.
* [https://archive.org/details/bitsavers_fullserviceGuide Sony/TEAC/Chinon Floppy Drive Service Manuals – Internet Archive]
 
Check the spindle flywheel's securing screw is tight before adjusting anything — a loose one causes a speed error that no adjustment will fix.<ref name="mzd" />
 
=== Track 0 ===
 
Track 0 detection is an optical or mechanical switch plus a mechanical stop. Clean it first. Adjust it only per the drive's own service procedure — Tandon's is Sections 5.9 and 5.10, with a defined switch position and a separate stop adjustment.<ref name="tandon" />
 
== Common faults ==
 
=== Drive will not read anything ===
 
In rough order of likelihood: fouled heads; perished or slipping belt; hardened rail lubricant; dirty track 0 sensor; spindle speed out of tolerance; bad media; and only then head or electronics failure.
 
Tandon's own checklist for intermittent ("soft") errors is worth following before condemning a drive: ensure proper earthing between power supply, drive and host; check for conducted and radiated electrical noise; confirm the ambient temperature is within specification; and verify the fault on a '''second''' diskette.<ref name="tandon" />
 
=== Drive pulls the machine's power supply down ===
 
Check the drive's own tantalum decoupling capacitors before suspecting the supply. On the Tandon TM100-2A these are '''C36 and C43''', 4.7 µF / 16 V, and they fail short.<ref name="mzd" /> Tantalums fail this way generally — see [[Capacitor Failure Symptoms]].
 
=== Eject and loading mechanism ===
 
* 3.5-inch Sony and Sony-derived mechanisms are known for hardened grease in the eject assembly and for cracked eject gears. The gear is a moulded plastic part that splits along the hub.
* Clean the old grease out completely before re-greasing; adding new grease on top of hardened old grease achieves nothing.
* Check the disk-present and write-protect microswitches or photo-interrupters. A drive that reports every disk as write-protected almost always has a dirty or failed write-protect sensor, not a fault in the host.
 
=== Erratic stepping ===
 
Symptom: read errors that vary with track number, or a carriage that moves unevenly. Cause: rail drag in almost every case. Clean and re-lubricate the rails before measuring the stepper. Measure the stepper's coil resistances only after that, and compare the phases against each other rather than against a remembered figure.
 
=== Termination and drive select ===
 
On Shugart-bus drives the '''terminator resistor pack goes in the last drive on the cable only''' — every other drive must have it removed.<ref name="tandon" /> Incorrect termination gives erratic behaviour rather than a clean failure, which makes it easy to misdiagnose. Drive-select jumpering varies by machine; read the drive's own service manual rather than a remembered convention.
 
== Media ==
 
The drive is only half the problem.
 
* '''Use the right disk.''' Double-density drives need double-density media; the IBM controller additionally requires '''soft-sectored''' disks.<ref name="mzd" />
* '''A disk that sheds oxide is finished''' and will foul the heads of every drive you put it in. Brown residue on the head, or a visible ring worn into the disk surface, is the sign.
* '''Never store a disk in the drive.''' On drives with a mechanical head-load or clamp this leaves the mechanism under load indefinitely.
* '''Image before you rely on it.''' Flux-level imaging hardware such as Greaseweazle or Kryoflux reads the raw transitions, which is both the best way to preserve original media and a good way to test a repaired drive against known-good images — see [[Recommended Tools]].
 
== Storage ==
 
Store drives dry, dust-free and at stable temperature. There is no evidence that periodically powering a drive "keeps the lubricant distributed": lubricant hardens with time and oxidation, not with disuse, and running a drive with hardened lubricant on its rails wears the rails.
 
== Manufacturer manuals on this wiki ==
 
* '''[[Service Support Tranning Programs Laserwriter Technical Procedures Jan 1985]]''' — despite its
  title, this Apple binder contains the '''DuoDisk''' and '''UniDisk Technical Procedures''', including
  the '''DuoDisk Analog Card Chip Swapping Chart''' (symptom → chip by grid position) and both drives'
  illustrated parts lists with Apple part numbers. It also carries Apple's warning that a DuoDisk
  analogue card connected to a computer '''with the power on''' will show "fuzz" and an exploded
  '''C21'''.<ref name="lwtp85">Apple Computer, ''Apple LaserWriter Printer Technical Procedures'', preliminary version for internal use only, sections stamped rev. Jan 85 and rev. Feb 85. Held on this wiki inside the Service Support Training Programs binder scan, described at [[Service Support Tranning Programs Laserwriter Technical Procedures Jan 1985]] ([[:File:Service_Support_Tranning_Programs_Laserwriter_Technical_Procedures_Jan_1985.pdf]]).</ref>
* '''[[Macintosh HDI-20 1.4 MB Drive Service Source]]''' — Apple's 18-page volume for the HDI-20
  external floppy drive. It is '''Troubleshooting and Take Apart only''': there is no Basics and no
  Specifications chapter, so it gives no capacity, data rate, current draw or mechanism part number.
  What it does give is the take-apart for the '''cable interface board''' and the HDI-20 external
  cable, which is the part that actually fails on these because the connector takes the strain.
* '''[[The Dead Mac Scrolls]]''' — Larry Pina's chapter 4 covers floppy drives, including
  '''replacing drive heads without test instruments''' (p. 265), which is the only published
  procedure of its kind held here.
For Apple's own external drives, the manufacturer's symptom chart is on this wiki: [[Apple SuperDrive/HDI-20 Service Source]] covers the external 1.4 MB SuperDrive and the HDI-20, and it is worth reading before condemning a mechanism because two of its entries are normal behaviour rather than faults.<ref name="sssuperfdr">''Apple SuperDrive'', Apple ''Service Source'', 21 pages - hosted on this wiki as [[Apple SuperDrive/HDI-20 Service Source]]. "MS-DOS drive does not recognize disk formatted on 1.4 MB SuperDrive" is answered by formatting all disks on the MS-DOS drive first, and "drive reads/writes to 800K disks but not to HD disks" begins with "verify that drive is 1.4 MB SuperDrive".</ref> The specifications for the 800K mechanism are in [[Apple 3.5 Drive Service Source]], and the 5.25-inch drive's 300 rpm and current figures in [[Apple PC 5.25 Drive Service Source]].
 
== Related pages ==
 
* [[Tandon TM100-1]] and [[Tandon TM100-2]] — worked examples with manufacturer figures
* [[IBM PS2 FDD Technical Reference (S42G-2194)]] — IBM's own 3.5-inch diskette drive technical reference, hosted here: the three interface pinouts, and a plain statement that IBM published no mechanical service data for these drives
* [[Hard Drive Maintenance and Repair]]
* [[Capacitor Failure Symptoms]]
* [[:Category:Capacitor Replacement Guides]]
* [[CRT Discharge Procedure]] — before opening any machine with a picture tube
* [[Recommended Tools]]
 
== References ==
<references />


[[Category:Repair Guides]]
[[Category:Repair Guides]]
[[Category:Storage Device Maintenance]]
[[Category:Storage Devices]]
[[Category:Floppy Drives]]

Latest revision as of 08:54, 25 September 2026

Floppy disk drives

Floppy disk drives were the main removable storage for vintage computers from the 1970s to the early 2000s. This page covers the faults that are common across manufacturers and the procedures that apply to most 5.25-inch and 3.5-inch mechanisms. For drive-specific figures — spindle speed tolerances, alignment limits, belt part numbers — go to the machine's own service manual; the Tandon TM100-2 page is a worked example with the manufacturer's real numbers.

Formats you are likely to meet:

  • 5.25-inch, 48 TPI, 40 tracks — IBM PC, Commodore, Apple II, Atari, Tandy. 250 KB unformatted per side; formatted as 160/180 KB single-sided or 320/360 KB double-sided on the PC.
  • 5.25-inch, 96 TPI, 80 tracks — the 1.2 MB "HD" drives of the PC/AT era.
  • 3.5-inch double density — 720 KB on the PC, 800 KB on the Macintosh and Amiga with different low-level formats.
  • 3.5-inch high density — 1.44 MB.

The single most useful thing to understand before starting: the vast majority of "dead" drives are not electrically dead. They are drives whose rail lubricant has hardened, whose heads are caked in oxide from a perished diskette, or whose belt has perished — and whose owner is testing them with the diskette that caused the problem.

Before you start

[edit | edit source]
  • Power off and unplug the machine or enclosure.
  • Wear an anti-static wrist strap with a current-limiting earth lead when handling the logic board — see Recommended Tools.
  • Note the ribbon cable orientation and the terminator/jumper configuration before removing anything.
  • Keep at least one known-good diskette that you have not used in the suspect drive. Testing a cleaned drive with the disk that fouled it is the classic trap.[1]

Cleaning

[edit | edit source]

The mechanism

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  • Blow out dust with a bulb blower or filtered compressed air.
  • Clean hardened lubricant off the head carriage rails with isopropyl alcohol and a lint-free cloth.
  • Inspect the belt; a belt that is glazed, slack or leaves black dust is finished.
  • On 5.25-inch single-sided drives, check the pressure pad opposite the head. A hardened, compressed or missing pad gives weak, intermittent reads.

The heads

[edit | edit source]

In practice:

  1. Start with a cleaning diskette. This is the manufacturer-sanctioned route. Cleaning diskettes are mildly abrasive, so use them when there is a reason to, not on a schedule.[1]
  2. Heavy oxide contamination — where a perished diskette has wiped a thick brown layer onto the heads — is beyond what a cleaning diskette will shift in one pass. Restorers do use isopropyl alcohol on a cotton tip here, very carefully, and report that clearing a thick layer can take minutes of patient work.[1] That is a considered departure from manufacturer guidance on a drive that is otherwise unusable. It is recorded so you know what you are trading; it is not this page's default advice.
  3. Never use a dry swab, abrasive, or a solvent other than isopropyl alcohol near the head.
  4. Throw the offending diskette away. A disk that sheds oxide will foul the heads again within seconds.[1]

Connectors

[edit | edit source]

Oxidised edge connectors and ribbon headers cause faults that look like drive faults. Clean the drive's edge connector, the controller card's edge connector and the ISA or expansion slot. A dielectric connector grease such as NyoGel 760G is designed for exactly this job — protecting contacts against fretting and corrosion, with a dielectric breakdown of 11.2 kV and a service range of −40 to 135 °C.[3] It is not a mechanism lubricant, despite being frequently recommended as one.

Lubrication

[edit | edit source]

What to use. For the head carriage rails, a silicone grease. That is the restoration-community consensus for the Tandon full-height drives and applies equally to most similar mechanisms.[1] Apply a thin film; the carriage should slide with no more resistance than the stepper's own detent.

What not to use, and why:

  • White lithium grease — widely repeated as the right choice for drive rails, but no drive manufacturer document consulted for this page specifies it.
  • NyoGel 760G and other connector greases — designed for electrical contacts, not sliding mechanisms.[3]
  • WD-40 — a water-displacing penetrant, not a lubricant. It thins existing grease, migrates to places you did not intend, and leaves a sticky residue as the carrier evaporates.
  • Oil on a stepper motor shaft — the shaft bearings are not a user-serviceable part and oil migrates onto the lead screw and into the optics.

No service interval. There is no manufacturer figure for re-greasing a floppy drive, and the honest answer is that a drive that is in regular use and moving freely does not need it. Re-lubricate when the carriage is stiff, when you have cleaned old lubricant off, or when the drive has come out of long storage — not on a calendar.

Alignment and adjustment

[edit | edit source]

Rule out everything else first. Alignment is the diagnosis of last resort. True alignment drift is indicated when both of these are true:

  1. Disks formatted in the drive read back correctly in that same drive, and
  2. The drive cannot read good disks formatted on a known-good, correctly aligned drive.[1]

Even then, the more likely causes are:

  • A dirty track 0 sensor. Chuck(G), quoted on minuszerodegrees, notes that many apparent alignment faults on these drives turn out to be a dirty track 0 sensor.[1] Clean the optics before touching anything adjustable.
  • Rail drag — the carriage not reaching the commanded cylinder.
  • Spindle speed out of tolerance.
  • The media. A double-density disk written or formatted in a high-density 1.2 MB drive does not meet the double-density standard and often cannot be read in a DD drive.[1]

Spindle speed

[edit | edit source]

The one adjustment that is safe to make. Tandon's specification for the TM100 series is 300 RPM ± 1.5 % — 295.5 to 304.5 RPM — adjusted at R4 on the servo board.[2][1] Most 300 RPM drives of the period share both the figure and the adjustment method. Three ways to measure:[1]

  1. The strobe rings moulded or printed on the spindle flywheel, one marked 50 Hz and one 60 Hz. Use the ring matching your mains frequency, under strong mains-powered fluorescent light. The pattern should stand still.
  2. ImageDisk's Test RPM command, or an equivalent utility.
  3. A digital oscilloscope with a frequency readout on the tachometer output of the speed-control IC.

Check the spindle flywheel's securing screw is tight before adjusting anything — a loose one causes a speed error that no adjustment will fix.[1]

Track 0

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Track 0 detection is an optical or mechanical switch plus a mechanical stop. Clean it first. Adjust it only per the drive's own service procedure — Tandon's is Sections 5.9 and 5.10, with a defined switch position and a separate stop adjustment.[2]

Common faults

[edit | edit source]

Drive will not read anything

[edit | edit source]

In rough order of likelihood: fouled heads; perished or slipping belt; hardened rail lubricant; dirty track 0 sensor; spindle speed out of tolerance; bad media; and only then head or electronics failure.

Tandon's own checklist for intermittent ("soft") errors is worth following before condemning a drive: ensure proper earthing between power supply, drive and host; check for conducted and radiated electrical noise; confirm the ambient temperature is within specification; and verify the fault on a second diskette.[2]

Drive pulls the machine's power supply down

[edit | edit source]

Check the drive's own tantalum decoupling capacitors before suspecting the supply. On the Tandon TM100-2A these are C36 and C43, 4.7 µF / 16 V, and they fail short.[1] Tantalums fail this way generally — see Capacitor Failure Symptoms.

Eject and loading mechanism

[edit | edit source]
  • 3.5-inch Sony and Sony-derived mechanisms are known for hardened grease in the eject assembly and for cracked eject gears. The gear is a moulded plastic part that splits along the hub.
  • Clean the old grease out completely before re-greasing; adding new grease on top of hardened old grease achieves nothing.
  • Check the disk-present and write-protect microswitches or photo-interrupters. A drive that reports every disk as write-protected almost always has a dirty or failed write-protect sensor, not a fault in the host.

Erratic stepping

[edit | edit source]

Symptom: read errors that vary with track number, or a carriage that moves unevenly. Cause: rail drag in almost every case. Clean and re-lubricate the rails before measuring the stepper. Measure the stepper's coil resistances only after that, and compare the phases against each other rather than against a remembered figure.

Termination and drive select

[edit | edit source]

On Shugart-bus drives the terminator resistor pack goes in the last drive on the cable only — every other drive must have it removed.[2] Incorrect termination gives erratic behaviour rather than a clean failure, which makes it easy to misdiagnose. Drive-select jumpering varies by machine; read the drive's own service manual rather than a remembered convention.

Media

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The drive is only half the problem.

  • Use the right disk. Double-density drives need double-density media; the IBM controller additionally requires soft-sectored disks.[1]
  • A disk that sheds oxide is finished and will foul the heads of every drive you put it in. Brown residue on the head, or a visible ring worn into the disk surface, is the sign.
  • Never store a disk in the drive. On drives with a mechanical head-load or clamp this leaves the mechanism under load indefinitely.
  • Image before you rely on it. Flux-level imaging hardware such as Greaseweazle or Kryoflux reads the raw transitions, which is both the best way to preserve original media and a good way to test a repaired drive against known-good images — see Recommended Tools.

Storage

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Store drives dry, dust-free and at stable temperature. There is no evidence that periodically powering a drive "keeps the lubricant distributed": lubricant hardens with time and oxidation, not with disuse, and running a drive with hardened lubricant on its rails wears the rails.

Manufacturer manuals on this wiki

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 title, this Apple binder contains the DuoDisk and UniDisk Technical Procedures, including
 the DuoDisk Analog Card Chip Swapping Chart (symptom → chip by grid position) and both drives'
 illustrated parts lists with Apple part numbers. It also carries Apple's warning that a DuoDisk
 analogue card connected to a computer with the power on will show "fuzz" and an exploded
 C21.[4]

 external floppy drive. It is Troubleshooting and Take Apart only: there is no Basics and no
 Specifications chapter, so it gives no capacity, data rate, current draw or mechanism part number.
 What it does give is the take-apart for the cable interface board and the HDI-20 external
 cable, which is the part that actually fails on these because the connector takes the strain.

 replacing drive heads without test instruments (p. 265), which is the only published
 procedure of its kind held here.

For Apple's own external drives, the manufacturer's symptom chart is on this wiki: Apple SuperDrive/HDI-20 Service Source covers the external 1.4 MB SuperDrive and the HDI-20, and it is worth reading before condemning a mechanism because two of its entries are normal behaviour rather than faults.[5] The specifications for the 800K mechanism are in Apple 3.5 Drive Service Source, and the 5.25-inch drive's 300 rpm and current figures in Apple PC 5.25 Drive Service Source.

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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 "Tandon TM100-2 in IBM 5150/5155/5160 — Known Problems/Issues", minuszerodegrees.net. Cited for: silicone-based lubricant (grease or spray) on the head carriage rails; the use of isopropyl alcohol on a cotton tip for heavy oxide build-up, against the manufacturer's caution, and the fact that head cleaning diskettes are themselves abrasive; the trap of re-testing with the diskette that fouled the heads; media requirements (double-sided, double-density, soft-sectored for the IBM controller) and the problem of double-density disks written in a high-density drive; spindle speed 295.5–304.5 RPM, the R4 speed adjustment and the 50 Hz / 60 Hz strobe rings on the spindle flywheel; loose spindle flywheel screw as a cause of speed error; C36 and C43 (4.7 µF / 16 V tantalum) as the first suspects when a drive overloads the host power supply; and Chuck(G)'s observation via VCFed that many apparent alignment faults are a dirty track 0 sensor. A strong community reference for IBM PC hardware, cited here as a secondary source.
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 Tandon TM100-1 / TM100-2 48 TPI Operating and Service Manuals, Tandon Corporation, manual part number 179022-001 Rev. B, July 1983 — hosted on this wiki as File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf. Section 6.1 and 6.2 (symptom diagnostic techniques and soft errors, including the caution against cleaning heads by hand and the soft-error checklist), section 5 (maintenance checks and adjustments, alignment tolerances, the Dysan 224/2A certified alignment diskette and the one-hour temperature stabilisation requirement), Table 2-1 (300 RPM ± 1.5 %, 250 kbit/s, seek and settling times) and Appendix A (spare parts list). Tandon's instructions are specific to its own drives but the head-handling caution reflects general practice of the period.
  3. ↑ 3.0 3.1 NyoGel® 760G — The Leading Connector Grease, Nye Lubricants (Fuchs). Cited for the product being a PAO/silica dielectric connector grease intended for electrical contacts — preventing fretting wear and corrosion and reducing mating force — with typical properties of −40 to 135 °C service range, kinematic viscosity 400 cSt at 40 °C and dielectric breakdown voltage 11.2 kV. It is not marketed as a mechanism, rail or gear lubricant.
  4. ↑ Apple Computer, Apple LaserWriter Printer Technical Procedures, preliminary version for internal use only, sections stamped rev. Jan 85 and rev. Feb 85. Held on this wiki inside the Service Support Training Programs binder scan, described at Service Support Tranning Programs Laserwriter Technical Procedures Jan 1985 (File:Service_Support_Tranning_Programs_Laserwriter_Technical_Procedures_Jan_1985.pdf).
  5. ↑ Apple SuperDrive, Apple Service Source, 21 pages - hosted on this wiki as Apple SuperDrive/HDI-20 Service Source. "MS-DOS drive does not recognize disk formatted on 1.4 MB SuperDrive" is answered by formatting all disks on the MS-DOS drive first, and "drive reads/writes to 800K disks but not to HD disks" begins with "verify that drive is 1.4 MB SuperDrive".
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