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= General Floppy Drive Repair Guide =
[[File:Floppy Disk Drives 8 5 3.jpg|thumb|Three generations of floppy drive: a Qume 8-inch drive, a Tandon TM100-2A 5.25-inch drive with IBM badge, and a 3.5-inch drive (photo: Michael Holley, public domain)]]
[[File:Floppy Disk Drives 8 5 3.jpg|thumb|Floppy Disk Drives]]
'''Floppy drive repair''' on vintage machines mostly means cleaning, checking the belt and the spindle speed, and finding the faults that look like drive failures but are not: bad media, a dirty track 0 sensor, a wrong terminator or a dirty connector. The manufacturers disagree on cleaning and lubrication, so the first step is to find the service manual for the drive in front of you. The table below lists drives whose service documents are hosted here, and the sections after it give what each manufacturer says.
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.
== Drives and their documents ==
* '''3.5" Double Density (DD, 720KB/800KB)''' – Used in IBM PCs, Macintosh, Atari ST, and Amiga computers.
<templatestyles src="Template:StyledTable/styles.css" />
* '''3.5" High Density (HD, 1.44MB)''' – Common in later IBM PC compatibles, Macintosh, and Amiga systems.
{| class="wikitable styled-table" style="width:100%; text-align:left;"
|+'''Floppy drives and their service documents'''
! Drive !! Used with !! Media !! Spindle drive !! Speed !! Source
|-
| Apple Disk II || [[Apple II]], II Plus, IIe, IIGS || 5.25-inch || Belt (Apple part U880-0002) || Set with Apple's DSPEED diagnostic || Apple ''Disk II Technical Procedures''<ref name="disk2tp" />
|-
| Tandon TM100-1 and TM100-2 || [[IBM PC (5150)|IBM PC]], [[IBM PC XT (5160)|PC XT]] || 5.25-inch, 48 TPI, 40 tracks || Belt (Tandon 914000-001) from a DC motor || 300 rpm ±1.5 %, adjusted at R4 || Tandon manual<ref name="tandon" />
|-
| Commodore VIC-1541 || [[Commodore 64]], VIC-20 || 5.25-inch || Belt from the drive motor to the flywheel || 300 rpm || Peltier, ''Commodore 1541 Troubleshooting & Repair Guide''<ref name="peltier" />
|-
| Apple PC 5.25 Drive || Apple || 5.25-inch, 48 TPI, 40 tracks, 360K || – || 300 rpm || Apple Service Source<ref name="sspc525" />
|-
| Amstrad DDI-1 and FD-1 (EME-150A mechanism) || [[Amstrad CPC 464|Amstrad CPC]] || 3-inch || Belt (Amstrad part 190015) || Index period 200 ±5 ms; adjust VR201 to 200 ±1 ms || Amstrad service manual<ref name="ddi1" />
|-
| Mitsubishi MF355C || [[IBM PS/2 Model 50|IBM PS/2]] || 3.5-inch, 1.44 MB || DC brushless direct drive, no belt || 300 rpm || Mitsubishi specification<ref name="mf355c" />
|-
| IBM 5120 diskette drives || [[IBM 5120]] || 8-inch || AC drive motor, belt and pulley || – || IBM ''Maintenance Information Manual''<ref name="ibm5120" />
|}


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.
The Tandon, Disk II and 1541 5.25-inch drives and the Amstrad 3-inch drive are belt-driven, so a perished belt is a real fault on them. The 3.5-inch drives of the PS/2 era are direct drive and have no belt.<ref name="mf355c" />


== Disassembly and Cleaning ==
== Before you start ==
* Switch off and unplug the machine. If it has a built-in picture tube (compact Macintosh, Osborne, Commodore PET), read [[CRT Discharge Procedure]] first.
* Use a grounded wrist strap and mat when handling boards, but not on plugged-in equipment or near an undischarged CRT.<ref name="applesg" />
* Check the supply voltages before suspecting the drive. Tandon's troubleshooting section starts there.<ref name="tandon" />
* If you can, prove the drive is the fault by substituting a known working drive. That rules out the controller, the cable, and dirty edge connectors on the controller card or in its slot.<ref name="mzd" />
* Keep a known-good diskette that has never been in the suspect drive. If a diskette is shedding oxide, cleaning the heads and then testing with the same diskette fouls them again.<ref name="mzd" />


=== Preparing for Maintenance ===
== Head cleaning ==
Before servicing any floppy drive:
The manufacturers' instructions conflict:
* 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:
<templatestyles src="Template:StyledTable/styles.css" />
* Unscrew the outer case or bracket holding the drive.
{| class="wikitable styled-table" style="width:100%; text-align:left;"
* Carefully disconnect the '''ribbon data cable''' and '''power cable'''.
|+'''What each document says about cleaning the heads'''
! Source !! Drive !! Instruction
|-
| Tandon, 1983 || TM100-1, TM100-2 || Quality media is usually enough to keep the heads clean. Where contamination is extreme, use a cleaning diskette according to its maker's instructions. "Do not use cotton swabs, solvents, or otherwise clean the head(s) by hand. Damage to the head(s) may result."<ref name="tandon" />
|-
| Apple, 1987 || Disk II || Clean the head with cotton swabs and isopropyl alcohol (80 % alcohol, 20 % water) whenever the drive is serviced, and inspect it for worn or dull spots in the ceramic.<ref name="disk2tp" />
|-
| Apple Service Source || SuperDrive, HDI-20 || "Clean drive" is the first action for read errors and failure to format; no method is given.<ref name="sssuper" /><ref name="sshdi20" />
|-
| IBM, 1979 || 5120 8-inch drives || The head/carriage assembly is adjusted and tested at the factory; no part of it is to be repaired or cleaned.<ref name="ibm5120" />
|-
| IBM || System/23 Datamaster (5322) drives || No preventive maintenance for the diskette drive; "do not repair or clean any part of" the head/carriage assembly.<ref name="ibm5322" />
|-
| Peltier (Sams), 1986 || Commodore 1541 || A cleaning disk, or manual cleaning with a lint-free cloth or foam and denatured alcohol. Use manual cleaning when a dirty head is causing problems; a cleaning disk can carry abrasive deposits back over the head.<ref name="peltier" />
|-
| Amstrad || DDI-1, FD-1 || Service agents are not to repair or adjust the mechanism or its board (PCB 30001) during warranty; a faulty mechanism goes back to Amstrad.<ref name="ddi1" />
|}


=== Cleaning the Drive Mechanism ===
Heavy oxide from a perished diskette is beyond what a cleaning diskette removes in one pass. minuszerodegrees.net, writing about the TM100-2, uses isopropyl alcohol on a cotton tip for this, very carefully, and reports that a thick layer can take a couple of minutes to remove. That goes against Tandon's caution, and the site also warns that cleaning diskettes are abrasive.<ref name="mzd" /> Throw away any diskette that is shedding oxide.<ref name="mzd" />
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 ==
== Rails and lubrication ==
Apple's Disk II procedure is to clean the head guide rails with isopropyl alcohol and "Do not use grease"; the head assembly should then move along its full travel without blockage or friction, or the mechanical assembly is replaced.<ref name="disk2tp" /> Tandon's TM100 manual gives no lubrication instruction.<ref name="tandon" /> IBM's Datamaster manual lists no preventive maintenance for its drives.<ref name="ibm5322" />


=== Track 0 Sensor Alignment ===
For the Tandon TM100-2, minuszerodegrees.net reports deteriorated lubricant on the head carriage rails as a common fault: the carriage moves badly or not at all. Its author cleans off the old lubricant and applies a silicone grease or spray, and notes that the spray tends to reach places it should not. With the power off, the carriage should move freely by hand against slight resistance from the stepper motor.<ref name="mzd" /> This is that site's own practice on the TM100, not a manufacturer instruction. Do not carry it over to a drive whose manufacturer says otherwise, such as the Disk II.
If the drive constantly clicks or cannot locate disk sectors:
* Locate the track zero sensor (optical or mechanical).
* Loosen its mounting screws and make small adjustments while testing a known-good disk.
* Tighten after proper alignment is restored.
[[File:Panasonic JU-268A016C-8166.jpg|thumb|Floppy Drive (Open) Read/Write Head]]


=== Read/Write Head Alignment ===
== Belts ==
If the drive can read its own formatted disks but not others:
Apple's Disk II procedure checks the motor drive belt for cracks, slippage and loss of elasticity whenever the drive is serviced, and replaces a belt that is dry, cracked or slipping.<ref name="disk2tp" /> Tandon lists "drive belt loose or missing" in its troubleshooting guide, and gives the belt removal and fitting procedure in section 6.4.<ref name="tandon" /> Peltier's 1541 guide says to inspect the belt for wear whenever the drive is open.<ref name="peltier" /> Amstrad's spindle motor replacement on the 3-inch drive starts by removing the belt, and ends with the index period reset at VR201.<ref name="ddi1" />
* 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.
== Spindle speed ==
* Tandon TM100: 300 rpm ±1.5 % (295.5 to 304.5 rpm), adjusted at R4 on the servo board.<ref name="tandon" /> minuszerodegrees describes three ways to measure it: the 50 Hz and 60 Hz strobe rings on the spindle flywheel under strong mains-powered fluorescent light, the Test RPM command in ImageDisk, or a digital oscilloscope on pin 2 of the servo board's LM2917. It also found a loose flywheel securing screw causing a speed error.<ref name="mzd" />
* Apple Disk II: run the DSPEED test of Apple's 5.25-inch Disk Drive Diagnostic with a known-good drive as drive 1 and the drive under test as drive 2, keep the drive flat, and turn the potentiometer on the motor control board at the back of the mechanism very slowly. If DSPEED cannot be brought into the "good" range, the mechanical assembly is replaced.<ref name="disk2tp" />
* Amstrad DDI-1 and FD-1: check that the index period is 200 ±5 ms; if not, adjust VR201 to 200 ±1 ms, and if it cannot be adjusted, check the supply and then the motor.<ref name="ddi1" />


== Common Floppy Drive Failures ==
== Alignment ==
{{Warning|'''Radial head alignment needs a certified alignment diskette, which 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 stand at room temperature for one hour before any check.<ref name="tandon" /> Amstrad's checks for the 3-inch drive use its EME-CF2 test disk and a double-beam oscilloscope.<ref name="ddi1" />}}


=== Drive Cannot Read Disks ===
minuszerodegrees gives the signs that a TM100-2 really has drifted: diskettes formatted in the drive work in that drive, but the drive will not read good diskettes formatted on a known-good drive. It advises against attempting alignment unless that is established, because the procedure can make the drive worse. It also quotes Chuck(G) on the VCFed forum: many apparent alignment faults on Tandon drives are "not alignment per se, but a dirty track 0 sensor".<ref name="mzd" /> Tandon's own track 0 procedures are sections 5.9 (track 0 switch) and 5.10 (track 0 stop).<ref name="tandon" />
Possible causes:
* '''Dirty or oxidized heads'''
* '''Failed or misaligned stepper motor'''
* '''Failed spindle motor'''
* '''Worn or demagnetized heads'''
* '''Defective floppy disks'''


Fix:
== Common faults ==
* Clean heads thoroughly.
<templatestyles src="Template:StyledTable/styles.css" />
* Test motors with a multimeter.
{| class="wikitable styled-table" style="width:100%; text-align:left;"
* Replace worn heads or motor with parts from a donor drive.
|+'''Faults and the manufacturer's or reference's action'''
! Drive !! Symptom !! Action, in the source's order
|-
| Disk II || Comes on but will not boot; I/O errors || Clean the head; adjust DSPEED; exchange the interface cable, then the analog card, then the mechanical assembly<ref name="disk2tp" />
|-
| Disk II || High-pitched whining || Exchange the mechanical assembly<ref name="disk2tp" />
|-
| Disk II || Writes to a write-protected diskette || Adjust the write-protect switch; exchange the analog card, then the mechanical assembly<ref name="disk2tp" />
|-
| DuoDisk || Fuzz on the analog card || Capacitor C21 has exploded, usually because the card was connected with the computer on; Apple returns the card<ref name="duodisk" />
|-
| DuoDisk (analog cards 676-[ ]101 and 676-[ ]102) || Data damaged when rebooting with Open Apple-Control-Reset, or with some copy-protected software, on a unit that passes the Drive Acceptance Program || Cut out C29 and C30 and do not replace them<ref name="duodisk" />
|-
| TM100 || Intermittent (soft) errors || Check grounding between supply, drive and host; check for conducted and radiated noise; check the ambient temperature; repeat on a second diskette<ref name="tandon" />
|-
| TM100-2A || Drive overloads the host's power supply || Suspect tantalum capacitors C36 and C43 (4.7 µF 16 V) first<ref name="mzd" />
|-
| Apple 3.5 Drive || Internal drive in a Macintosh Plus ejects continuously || The drive cable must have a yellow stripe, not a red one<ref name="ss35" />
|-
| Apple 3.5 Drive || Drives chained to a DuoDisk or UniDisk 5.25 spin up and become inaccessible from an Apple IIGS || Replace a Revision A daisy-chain board (gate array CXD1085A) with Revision B (CXD1085B)<ref name="ss35" />
|-
| SuperDrive || A PC drive will not read a disk formatted on the SuperDrive || Format the disk on the MS-DOS drive first<ref name="sssuper" />
|}


=== Eject Mechanism Issues ===
For the [[Disk II]] analog card, Apple's Technical Procedures go down to the chip: see the Disk II page. The DuoDisk analog card's chip-swapping chart is on [[Apple Floppy Disk Drive]].
Symptoms:
* Drive won't eject the disk.
* Constant clicking or eject cycling.


Fix:
== Termination and configuration ==
* Lubricate mechanical eject gears.
On Shugart-interface drives such as the TM100, the terminator resistor pack is fitted only in the last drive on the daisy chain; every other drive must have it removed.<ref name="tandon" /> Osborne's Field Service Manual notes the same arrangement inside the Osborne 1: the A drive carries an 8-pin 150 Ω terminator and the B drive does not, so a replacement A drive needs the terminator moved across from the old one.<ref name="osbfsm" /> Some wrong termination arrangements cause improper drive operation.<ref name="mzd" />
* Replace worn or cracked gears (common on Sony drives).
* Clean eject switch contacts or sensors.


=== Mechanical Wear or “Slipping” ===
Upgrading a machine to a high-density drive can need more than the drive. Atari's 1.44 MB kit for the [[Atari Mega STE]] (CA401229-001) also replaces the floppy controller at U405 with the AJAX chip, the PAL at UA2, and the TOS ROMs (to 2.06), and on main boards below revision B adds a jumper from U7 pin 32 to UA2 pin 19.<ref name="atarihd" />
Symptoms:
* Drive fails intermittently.
* Disk reads fail only under certain angles or temperatures.


Fix:
== Connectors ==
* Check head spring tension.
Dirty edge connectors on the controller card or in its slot cause faults that look like a failed drive.<ref name="mzd" /> Apple's Disk II procedure says not to use an eraser on gold contacts: use only a liquid or spray contact cleaner and a clean cloth.<ref name="disk2tp" />
* Ensure rails are lubricated and carriage moves smoothly.
* Verify correct operation of optical or mechanical limit switches.


=== Stepper Motor Failures ===
== Media ==
Stepper motors move the head between disk tracks. Symptoms of failure:
* Use the media the drive was designed for. The TM100-2 needs double-sided, double-density diskettes, and the IBM PC controller also needs them soft-sectored.<ref name="mzd" />
* Head doesn’t move.
* A double-density diskette written or formatted in a high-density drive does not meet the double-density standard and may not read in a double-density drive.<ref name="mzd" />
* Drive seeks incorrectly or makes erratic noises.
* IBM's PS/2 diskette reference warns that 1.0 MB media can be reliably formatted only to 720 KB, 2.0 MB media only to 1.44 MB, and 4.0 MB media only to 2.88 MB.<ref name="ibmfdd" />
* Peltier lists handling rules for the 1541: do not touch the head, keep diskettes away from transformers, motors and monitors, and do not put a defective diskette in the drive.<ref name="peltier" />


Fix:
Flux-level readers such as Greaseweazle read the raw data on almost any type of floppy disk, which is useful both for preserving original media and for testing a repaired drive.<ref name="gw" />
* 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 ==
== Manufacturer manuals on this wiki ==
* [[Tandon TM100-1]] and [[Tandon TM100-2]]: the drive pages, with Tandon's figures.
* [[Apple 3.5 Drive Service Source]], [[Apple 800K Drive Service Source]], [[Apple PC 5.25 Drive Service Source]], [[Apple SuperDrive/HDI-20 Service Source]] and [[Macintosh HDI-20 1.4 MB Drive Service Source]]: Apple's symptom charts and take-apart procedures for its external drives.
* [[Service Support Training Programs LaserWriter Technical Procedures Jan 1985]]: despite the title, this Apple binder also holds the DuoDisk Technical Procedures and the UniDisk 5.25 section.<ref name="duodisk" />
* [[IBM PS2 FDD Technical Reference (S42G-2194)]]: IBM's interface and programming reference for the 720 KB, 1.44 MB and 2.88 MB PS/2 drives, with the connector pin assignments. It contains no mechanical service information.<ref name="ibmfdd" />
* [[Amstrad DDI-1 / FD-1 Service Manual]]: flowcharts, alignment checks and parts lists for the 3-inch drives.<ref name="ddi1" />
* [[Commodore 1541 Troubleshooting & Repair Guide]] and [[The Anatomy of the 1541 Disk Drive]] for the Commodore 1541.
* [[Atari Mega STE 1.44MB Floppy Drive Installation Manual]].<ref name="atarihd" />
* [[The Dead Mac Scrolls]]: chapter 4 covers floppy drives, including replacing drive heads without test instruments (p. 265).<ref name="dms" />


For smooth operation:
== Related pages ==
* Lubricate rails, gears, and eject cams with '''Nyogel 760G''' or similar synthetic grease.
* [[Hard Drive Maintenance and Repair]]
* Avoid petroleum-based products like '''WD-40''', which break down plastics and gunk up over time.
* [[Capacitor Failure Symptoms]]
* Reapply grease every 2–3 years depending on use.
* [[:Category:Capacitor Replacement Guides]]
 
* [[CRT Discharge Procedure]]
== Troubleshooting Specific Drive Types ==
* [[Recommended Tools]]
[[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) ===
* Common in Macintosh, Amiga, and IBM PC systems.
* 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) ===
* 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 ==
 
* Periodically power up drives to keep lubricants distributed.
* 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 ==


* [[Capacitor Replacement Guides]]
== References ==
* [[CRT Discharge Procedure]]
<references>
* [[Macintosh HDD Maintenance]]
<ref name="tandon">Tandon Corporation, ''OEM Operating and Service Manual, TM100-1, TM100-2 Disk Drives, 48 Tracks per Inch'', part number 179022-001, July 1983: section 1 (daisy chaining; last drive terminates), Table 2-1 (300 rpm ±1.5 %), section 3 (terminator resistor pack RP1), section 5 (alignment with the Dysan 224/2A, one-hour stabilisation; 5.9 and 5.10 track 0 switch and stop; R4 speed control), section 6.1–6.4 (check supply voltages first; soft errors; head-cleaning caution; troubleshooting guide; drive belt replacement) and Appendix A (drive belt 914000-001). The manual has no lubrication instruction. Hosted as [[:File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf]].</ref>
* [https://archive.org/details/bitsavers_fullserviceGuide Sony/TEAC/Chinon Floppy Drive Service Manuals – Internet Archive]
<ref name="disk2tp">Apple Computer, ''Disk II Technical Procedures'' (rev. Feb 87), from ''Apple Service Technical Procedures: Apple II/Apple III Archived Products, Volume One'' (072-0231): symptom chart p. 2.3; analog card troubleshooting pp. 2.4–2.8 (gold contacts p. 2.5); DSPEED adjustment pp. 3.3–3.4; preventive maintenance pp. 4.2–4.4 (head and rails with isopropyl alcohol, "Do not use grease"; head load button; motor drive belt); parts list pp. 5.3–5.7 (belt U880-0002). Hosted as [[:File:Apple Disk II Technical Procedures.pdf]].</ref>
<ref name="duodisk">Apple Computer, ''DuoDisk Technical Procedures'', Section 1, Troubleshooting (rev. Aug 85), pp. 1.2 (general information; C29/C30), 1.4 (inspection of the 74LS125 and C21) and 1.5 (chip swapping chart). Bound in the Apple Service Support Training Programs binder described at [[Service Support Training Programs LaserWriter Technical Procedures Jan 1985]] ([[:File:Service Support Tranning Programs Laserwriter Technical Procedures Jan 1985.pdf|PDF]], PDF pp. 165–170).</ref>
<ref name="mzd">minuszerodegrees.net, [https://www.minuszerodegrees.net/5150_5160/tandon_tm100/tandon_tm100-2_problems.htm "Tandon TM100-2 in IBM 5150/5155/5160 – Known Problems/Issues"], retrieved 2026-10-01. Community reference; the lubrication and head-cleaning advice is the author's own practice on the TM100-2.</ref>
<ref name="peltier">Michael G. Peltier, ''Commodore 1541 Troubleshooting & Repair Guide'', Howard W. Sams, 1986, ISBN 0-672-22470-4: section 2.2.3 (drive system, belt), p. 19; section 4 (preventive maintenance, handling and head cleaning), pp. 44–46; drive motor servo (300 rpm), p. 157. Hosted as [[Commodore 1541 Troubleshooting & Repair Guide]].</ref>
<ref name="sspc525">Apple Computer, ''Apple PC 5.25 Drive'' (Service Source), Specifications. Hosted as [[Apple PC 5.25 Drive Service Source]].</ref>
<ref name="ddi1">Amstrad, ''DDI1 / FD1 Service Manual'': cabinet parts list (Compact FDD EME-150A, drive belt 190015), p. 3; diagnostic flow chart, pp. 5–8 (index period 200 ±5 ms; adjust VR201 to 200 ±1 ms; warranty note); alignment checks with the EME-CF2 test disk; mechanical replacements. Hosted as [[Amstrad DDI-1 / FD-1 Service Manual]].</ref>
<ref name="mf355c">Mitsubishi Electric, ''3.5 inch Flexible Disk Drive Standard Specifications, MF355C'', UGD-0527A, February 1987, sections 1 and 3 (DC brushless direct-drive motor, 300 rpm). Hosted as [[:File:Mitsubishi MF355C 3.5 inch Diskette Drive Specifications (UGD-0527A, Feb 1987).pdf]].</ref>
<ref name="ibm5120">IBM, ''5120 Computing System Maintenance Information Manual'', SY34-0192-0, December 1979, item 225 "Head/Carriage Assembly", pp. 2-26 to 2-31, and items 229 and 231 (AC drive motor; drive belt and pulley), pp. 2-40 to 2-43. Hosted as [[IBM 5120 Maintenance Information Manual]].</ref>
<ref name="ibm5322">IBM, ''5322 Computer Service Manual'', SY34-0171-0, p. 5-3, maintenance preface. Hosted as [[IBM 5322 Computer Service Manual]].</ref>
<ref name="ibmfdd">IBM, ''Personal System/2 3.5-inch Diskette Drives Technical Reference'', S42G-2194-00: description and media warning, pp. 1–2; connectors, p. 7. Hosted as [[IBM PS2 FDD Technical Reference (S42G-2194)]].</ref>
<ref name="ss35">Apple Computer, ''Apple 3.5 Drive'' (Service Source), Troubleshooting, Symptom Charts/Miscellaneous. Hosted as [[Apple 3.5 Drive Service Source]].</ref>
<ref name="sssuper">Apple Computer, ''Apple SuperDrive'' (Service Source), Troubleshooting, Symptom Charts. Hosted as [[Apple SuperDrive/HDI-20 Service Source]].</ref>
<ref name="sshdi20">Apple Computer, ''Macintosh HDI-20 1.4 MB Drive'' (Service Source), Troubleshooting, Symptom Charts. Hosted as [[Macintosh HDI-20 1.4 MB Drive Service Source]].</ref>
<ref name="applesg">Apple Computer, ''Apple Service Guide: Macintosh Computers'', 1990, pp. 1 and 5–6 (ESD prevention rules; do not be grounded when working on plugged-in equipment or an undischarged CRT). Hosted as [[Apple Macintosh Service Guide Volume 1 1990]].</ref>
<ref name="osbfsm">Osborne Computer Corporation, ''Osborne Field Service Manual'', 2nd edition, 1983, section 6.1.5 (Disk Drive "A" Disassembly), pp. 52–53. Hosted as [[Osborne Field Service Manual (Revision 2.0)]].</ref>
<ref name="atarihd">Atari Corporation, ''MEGA STe 1.44 Megabyte Floppy Drive Installation Manual'', C302953-001, 1991, kit contents and installation steps 3–9. Hosted as [[Atari Mega STE 1.44MB Floppy Drive Installation Manual]].</ref>
<ref name="gw">Keir Fraser, [https://github.com/keirf/greaseweazle Greaseweazle host tools], GitHub, retrieved 2026-10-01.</ref>
<ref name="dms">Larry Pina, ''The Dead Mac Scrolls'', Peachpit Press, 1992, chapter 4 "Floppy disk drives", pp. 243–276. Hosted as [[The Dead Mac Scrolls]].</ref>
</references>


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

Latest revision as of 19:28, 1 October 2026

Three generations of floppy drive: a Qume 8-inch drive, a Tandon TM100-2A 5.25-inch drive with IBM badge, and a 3.5-inch drive (photo: Michael Holley, public domain)

Floppy drive repair on vintage machines mostly means cleaning, checking the belt and the spindle speed, and finding the faults that look like drive failures but are not: bad media, a dirty track 0 sensor, a wrong terminator or a dirty connector. The manufacturers disagree on cleaning and lubrication, so the first step is to find the service manual for the drive in front of you. The table below lists drives whose service documents are hosted here, and the sections after it give what each manufacturer says.

Drives and their documents

[edit | edit source]
Floppy drives and their service documents
Drive Used with Media Spindle drive Speed Source
Apple Disk II Apple II, II Plus, IIe, IIGS 5.25-inch Belt (Apple part U880-0002) Set with Apple's DSPEED diagnostic Apple Disk II Technical Procedures[1]
Tandon TM100-1 and TM100-2 IBM PC, PC XT 5.25-inch, 48 TPI, 40 tracks Belt (Tandon 914000-001) from a DC motor 300 rpm ±1.5 %, adjusted at R4 Tandon manual[2]
Commodore VIC-1541 Commodore 64, VIC-20 5.25-inch Belt from the drive motor to the flywheel 300 rpm Peltier, Commodore 1541 Troubleshooting & Repair Guide[3]
Apple PC 5.25 Drive Apple 5.25-inch, 48 TPI, 40 tracks, 360K – 300 rpm Apple Service Source[4]
Amstrad DDI-1 and FD-1 (EME-150A mechanism) Amstrad CPC 3-inch Belt (Amstrad part 190015) Index period 200 ±5 ms; adjust VR201 to 200 ±1 ms Amstrad service manual[5]
Mitsubishi MF355C IBM PS/2 3.5-inch, 1.44 MB DC brushless direct drive, no belt 300 rpm Mitsubishi specification[6]
IBM 5120 diskette drives IBM 5120 8-inch AC drive motor, belt and pulley – IBM Maintenance Information Manual[7]

The Tandon, Disk II and 1541 5.25-inch drives and the Amstrad 3-inch drive are belt-driven, so a perished belt is a real fault on them. The 3.5-inch drives of the PS/2 era are direct drive and have no belt.[6]

Before you start

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  • Switch off and unplug the machine. If it has a built-in picture tube (compact Macintosh, Osborne, Commodore PET), read CRT Discharge Procedure first.
  • Use a grounded wrist strap and mat when handling boards, but not on plugged-in equipment or near an undischarged CRT.[8]
  • Check the supply voltages before suspecting the drive. Tandon's troubleshooting section starts there.[2]
  • If you can, prove the drive is the fault by substituting a known working drive. That rules out the controller, the cable, and dirty edge connectors on the controller card or in its slot.[9]
  • Keep a known-good diskette that has never been in the suspect drive. If a diskette is shedding oxide, cleaning the heads and then testing with the same diskette fouls them again.[9]

Head cleaning

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The manufacturers' instructions conflict:

What each document says about cleaning the heads
Source Drive Instruction
Tandon, 1983 TM100-1, TM100-2 Quality media is usually enough to keep the heads clean. Where contamination is extreme, use a cleaning diskette according to its maker's instructions. "Do not use cotton swabs, solvents, or otherwise clean the head(s) by hand. Damage to the head(s) may result."[2]
Apple, 1987 Disk II Clean the head with cotton swabs and isopropyl alcohol (80 % alcohol, 20 % water) whenever the drive is serviced, and inspect it for worn or dull spots in the ceramic.[1]
Apple Service Source SuperDrive, HDI-20 "Clean drive" is the first action for read errors and failure to format; no method is given.[10][11]
IBM, 1979 5120 8-inch drives The head/carriage assembly is adjusted and tested at the factory; no part of it is to be repaired or cleaned.[7]
IBM System/23 Datamaster (5322) drives No preventive maintenance for the diskette drive; "do not repair or clean any part of" the head/carriage assembly.[12]
Peltier (Sams), 1986 Commodore 1541 A cleaning disk, or manual cleaning with a lint-free cloth or foam and denatured alcohol. Use manual cleaning when a dirty head is causing problems; a cleaning disk can carry abrasive deposits back over the head.[3]
Amstrad DDI-1, FD-1 Service agents are not to repair or adjust the mechanism or its board (PCB 30001) during warranty; a faulty mechanism goes back to Amstrad.[5]

Heavy oxide from a perished diskette is beyond what a cleaning diskette removes in one pass. minuszerodegrees.net, writing about the TM100-2, uses isopropyl alcohol on a cotton tip for this, very carefully, and reports that a thick layer can take a couple of minutes to remove. That goes against Tandon's caution, and the site also warns that cleaning diskettes are abrasive.[9] Throw away any diskette that is shedding oxide.[9]

Rails and lubrication

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Apple's Disk II procedure is to clean the head guide rails with isopropyl alcohol and "Do not use grease"; the head assembly should then move along its full travel without blockage or friction, or the mechanical assembly is replaced.[1] Tandon's TM100 manual gives no lubrication instruction.[2] IBM's Datamaster manual lists no preventive maintenance for its drives.[12]

For the Tandon TM100-2, minuszerodegrees.net reports deteriorated lubricant on the head carriage rails as a common fault: the carriage moves badly or not at all. Its author cleans off the old lubricant and applies a silicone grease or spray, and notes that the spray tends to reach places it should not. With the power off, the carriage should move freely by hand against slight resistance from the stepper motor.[9] This is that site's own practice on the TM100, not a manufacturer instruction. Do not carry it over to a drive whose manufacturer says otherwise, such as the Disk II.

Belts

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Apple's Disk II procedure checks the motor drive belt for cracks, slippage and loss of elasticity whenever the drive is serviced, and replaces a belt that is dry, cracked or slipping.[1] Tandon lists "drive belt loose or missing" in its troubleshooting guide, and gives the belt removal and fitting procedure in section 6.4.[2] Peltier's 1541 guide says to inspect the belt for wear whenever the drive is open.[3] Amstrad's spindle motor replacement on the 3-inch drive starts by removing the belt, and ends with the index period reset at VR201.[5]

Spindle speed

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  • Tandon TM100: 300 rpm ±1.5 % (295.5 to 304.5 rpm), adjusted at R4 on the servo board.[2] minuszerodegrees describes three ways to measure it: the 50 Hz and 60 Hz strobe rings on the spindle flywheel under strong mains-powered fluorescent light, the Test RPM command in ImageDisk, or a digital oscilloscope on pin 2 of the servo board's LM2917. It also found a loose flywheel securing screw causing a speed error.[9]
  • Apple Disk II: run the DSPEED test of Apple's 5.25-inch Disk Drive Diagnostic with a known-good drive as drive 1 and the drive under test as drive 2, keep the drive flat, and turn the potentiometer on the motor control board at the back of the mechanism very slowly. If DSPEED cannot be brought into the "good" range, the mechanical assembly is replaced.[1]
  • Amstrad DDI-1 and FD-1: check that the index period is 200 ±5 ms; if not, adjust VR201 to 200 ±1 ms, and if it cannot be adjusted, check the supply and then the motor.[5]

Alignment

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minuszerodegrees gives the signs that a TM100-2 really has drifted: diskettes formatted in the drive work in that drive, but the drive will not read good diskettes formatted on a known-good drive. It advises against attempting alignment unless that is established, because the procedure can make the drive worse. It also quotes Chuck(G) on the VCFed forum: many apparent alignment faults on Tandon drives are "not alignment per se, but a dirty track 0 sensor".[9] Tandon's own track 0 procedures are sections 5.9 (track 0 switch) and 5.10 (track 0 stop).[2]

Common faults

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Faults and the manufacturer's or reference's action
Drive Symptom Action, in the source's order
Disk II Comes on but will not boot; I/O errors Clean the head; adjust DSPEED; exchange the interface cable, then the analog card, then the mechanical assembly[1]
Disk II High-pitched whining Exchange the mechanical assembly[1]
Disk II Writes to a write-protected diskette Adjust the write-protect switch; exchange the analog card, then the mechanical assembly[1]
DuoDisk Fuzz on the analog card Capacitor C21 has exploded, usually because the card was connected with the computer on; Apple returns the card[13]
DuoDisk (analog cards 676-[ ]101 and 676-[ ]102) Data damaged when rebooting with Open Apple-Control-Reset, or with some copy-protected software, on a unit that passes the Drive Acceptance Program Cut out C29 and C30 and do not replace them[13]
TM100 Intermittent (soft) errors Check grounding between supply, drive and host; check for conducted and radiated noise; check the ambient temperature; repeat on a second diskette[2]
TM100-2A Drive overloads the host's power supply Suspect tantalum capacitors C36 and C43 (4.7 µF 16 V) first[9]
Apple 3.5 Drive Internal drive in a Macintosh Plus ejects continuously The drive cable must have a yellow stripe, not a red one[14]
Apple 3.5 Drive Drives chained to a DuoDisk or UniDisk 5.25 spin up and become inaccessible from an Apple IIGS Replace a Revision A daisy-chain board (gate array CXD1085A) with Revision B (CXD1085B)[14]
SuperDrive A PC drive will not read a disk formatted on the SuperDrive Format the disk on the MS-DOS drive first[10]

For the Disk II analog card, Apple's Technical Procedures go down to the chip: see the Disk II page. The DuoDisk analog card's chip-swapping chart is on Apple Floppy Disk Drive.

Termination and configuration

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On Shugart-interface drives such as the TM100, the terminator resistor pack is fitted only in the last drive on the daisy chain; every other drive must have it removed.[2] Osborne's Field Service Manual notes the same arrangement inside the Osborne 1: the A drive carries an 8-pin 150 Ω terminator and the B drive does not, so a replacement A drive needs the terminator moved across from the old one.[15] Some wrong termination arrangements cause improper drive operation.[9]

Upgrading a machine to a high-density drive can need more than the drive. Atari's 1.44 MB kit for the Atari Mega STE (CA401229-001) also replaces the floppy controller at U405 with the AJAX chip, the PAL at UA2, and the TOS ROMs (to 2.06), and on main boards below revision B adds a jumper from U7 pin 32 to UA2 pin 19.[16]

Connectors

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Dirty edge connectors on the controller card or in its slot cause faults that look like a failed drive.[9] Apple's Disk II procedure says not to use an eraser on gold contacts: use only a liquid or spray contact cleaner and a clean cloth.[1]

Media

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  • Use the media the drive was designed for. The TM100-2 needs double-sided, double-density diskettes, and the IBM PC controller also needs them soft-sectored.[9]
  • A double-density diskette written or formatted in a high-density drive does not meet the double-density standard and may not read in a double-density drive.[9]
  • IBM's PS/2 diskette reference warns that 1.0 MB media can be reliably formatted only to 720 KB, 2.0 MB media only to 1.44 MB, and 4.0 MB media only to 2.88 MB.[17]
  • Peltier lists handling rules for the 1541: do not touch the head, keep diskettes away from transformers, motors and monitors, and do not put a defective diskette in the drive.[3]

Flux-level readers such as Greaseweazle read the raw data on almost any type of floppy disk, which is useful both for preserving original media and for testing a repaired drive.[18]

Manufacturer manuals on this wiki

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References

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  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 Apple Computer, Disk II Technical Procedures (rev. Feb 87), from Apple Service Technical Procedures: Apple II/Apple III Archived Products, Volume One (072-0231): symptom chart p. 2.3; analog card troubleshooting pp. 2.4–2.8 (gold contacts p. 2.5); DSPEED adjustment pp. 3.3–3.4; preventive maintenance pp. 4.2–4.4 (head and rails with isopropyl alcohol, "Do not use grease"; head load button; motor drive belt); parts list pp. 5.3–5.7 (belt U880-0002). Hosted as File:Apple Disk II Technical Procedures.pdf.
  2. ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 Tandon Corporation, OEM Operating and Service Manual, TM100-1, TM100-2 Disk Drives, 48 Tracks per Inch, part number 179022-001, July 1983: section 1 (daisy chaining; last drive terminates), Table 2-1 (300 rpm ±1.5 %), section 3 (terminator resistor pack RP1), section 5 (alignment with the Dysan 224/2A, one-hour stabilisation; 5.9 and 5.10 track 0 switch and stop; R4 speed control), section 6.1–6.4 (check supply voltages first; soft errors; head-cleaning caution; troubleshooting guide; drive belt replacement) and Appendix A (drive belt 914000-001). The manual has no lubrication instruction. Hosted as File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf.
  3. ↑ 3.0 3.1 3.2 3.3 Michael G. Peltier, Commodore 1541 Troubleshooting & Repair Guide, Howard W. Sams, 1986, ISBN 0-672-22470-4: section 2.2.3 (drive system, belt), p. 19; section 4 (preventive maintenance, handling and head cleaning), pp. 44–46; drive motor servo (300 rpm), p. 157. Hosted as Commodore 1541 Troubleshooting & Repair Guide.
  4. ↑ Apple Computer, Apple PC 5.25 Drive (Service Source), Specifications. Hosted as Apple PC 5.25 Drive Service Source.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 Amstrad, DDI1 / FD1 Service Manual: cabinet parts list (Compact FDD EME-150A, drive belt 190015), p. 3; diagnostic flow chart, pp. 5–8 (index period 200 ±5 ms; adjust VR201 to 200 ±1 ms; warranty note); alignment checks with the EME-CF2 test disk; mechanical replacements. Hosted as Amstrad DDI-1 / FD-1 Service Manual.
  6. ↑ 6.0 6.1 Mitsubishi Electric, 3.5 inch Flexible Disk Drive Standard Specifications, MF355C, UGD-0527A, February 1987, sections 1 and 3 (DC brushless direct-drive motor, 300 rpm). Hosted as File:Mitsubishi MF355C 3.5 inch Diskette Drive Specifications (UGD-0527A, Feb 1987).pdf.
  7. ↑ 7.0 7.1 IBM, 5120 Computing System Maintenance Information Manual, SY34-0192-0, December 1979, item 225 "Head/Carriage Assembly", pp. 2-26 to 2-31, and items 229 and 231 (AC drive motor; drive belt and pulley), pp. 2-40 to 2-43. Hosted as IBM 5120 Maintenance Information Manual.
  8. ↑ Apple Computer, Apple Service Guide: Macintosh Computers, 1990, pp. 1 and 5–6 (ESD prevention rules; do not be grounded when working on plugged-in equipment or an undischarged CRT). Hosted as Apple Macintosh Service Guide Volume 1 1990.
  9. ↑ 9.00 9.01 9.02 9.03 9.04 9.05 9.06 9.07 9.08 9.09 9.10 9.11 minuszerodegrees.net, "Tandon TM100-2 in IBM 5150/5155/5160 – Known Problems/Issues", retrieved 2026-10-01. Community reference; the lubrication and head-cleaning advice is the author's own practice on the TM100-2.
  10. ↑ 10.0 10.1 Apple Computer, Apple SuperDrive (Service Source), Troubleshooting, Symptom Charts. Hosted as Apple SuperDrive/HDI-20 Service Source.
  11. ↑ Apple Computer, Macintosh HDI-20 1.4 MB Drive (Service Source), Troubleshooting, Symptom Charts. Hosted as Macintosh HDI-20 1.4 MB Drive Service Source.
  12. ↑ 12.0 12.1 IBM, 5322 Computer Service Manual, SY34-0171-0, p. 5-3, maintenance preface. Hosted as IBM 5322 Computer Service Manual.
  13. ↑ 13.0 13.1 13.2 Apple Computer, DuoDisk Technical Procedures, Section 1, Troubleshooting (rev. Aug 85), pp. 1.2 (general information; C29/C30), 1.4 (inspection of the 74LS125 and C21) and 1.5 (chip swapping chart). Bound in the Apple Service Support Training Programs binder described at Service Support Training Programs LaserWriter Technical Procedures Jan 1985 (PDF, PDF pp. 165–170).
  14. ↑ 14.0 14.1 Apple Computer, Apple 3.5 Drive (Service Source), Troubleshooting, Symptom Charts/Miscellaneous. Hosted as Apple 3.5 Drive Service Source.
  15. ↑ Osborne Computer Corporation, Osborne Field Service Manual, 2nd edition, 1983, section 6.1.5 (Disk Drive "A" Disassembly), pp. 52–53. Hosted as Osborne Field Service Manual (Revision 2.0).
  16. ↑ 16.0 16.1 Atari Corporation, MEGA STe 1.44 Megabyte Floppy Drive Installation Manual, C302953-001, 1991, kit contents and installation steps 3–9. Hosted as Atari Mega STE 1.44MB Floppy Drive Installation Manual.
  17. ↑ 17.0 17.1 IBM, Personal System/2 3.5-inch Diskette Drives Technical Reference, S42G-2194-00: description and media warning, pp. 1–2; connectors, p. 7. Hosted as IBM PS2 FDD Technical Reference (S42G-2194).
  18. ↑ Keir Fraser, Greaseweazle host tools, GitHub, retrieved 2026-10-01.
  19. ↑ Larry Pina, The Dead Mac Scrolls, Peachpit Press, 1992, chapter 4 "Floppy disk drives", pp. 243–276. Hosted as The Dead Mac Scrolls.
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