Tandon TM100-1
| Tandon TM100-1 | |
|---|---|
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|
| A TM100-series drive on the cover of Tandon's 1983 TM100-1/TM100-2 manual | |
| Manufacturer | Tandon Corporation |
| Type | Full-height 5.25-inch floppy disk drive, single-sided, 48 TPI |
| Interface | 34-pin edge connector; 4-pin AMP power connector |
| Compatible | Very early IBM PC (5150) |
| Dimensions | 86 x 149 x 203 mm (IBM) |
| Weight | 2.04 kg (IBM) |
| Model | TM100-1 |
| Storage | 250 KB unformatted; 160 KB under DOS 1.x, 180 KB under DOS 2.0 and later |
| Media | 5.25-inch single-sided double-density soft-sectored diskette, 40 tracks |
The Tandon TM100-1 is a full-height 5.25-inch single-sided floppy disk drive with 40 tracks at 48 tracks per inch. It has one read/write head. The double-sided Tandon TM100-2 is the same drive with a second head, and Tandon documents both in one manual.[1] The single-sided drive was fitted to very early IBM PCs, which IBM sold with a "160 KB Diskette Drive"; DOS 1.1, released in May 1982, added support for double-sided drives.[2][3]
Specifications
[edit | edit source]| Parameter | Value |
|---|---|
| Heads | 1 |
| Tracks | 40, at 48 TPI |
| Track spacing | 0.529 mm (20.8 mil) |
| Unformatted capacity | 250 KB per disk |
| Recording modes | FM, MFM, MMFM |
| Data transfer rate | 250,000 bit/s, double density |
| Flux reversals per inch, inside track | 5,535 |
| Rotational speed | 300 RPM ± 1.5 % |
| Instantaneous speed variation | ± 3 % |
| Average rotational latency | 100 ms |
| Motor start / stop time | 250 ms / 150 ms maximum |
| Seek time, track to track | 5 ms |
| Head settling time | 15 ms |
| Average access time, including settling | 75 ms |
| Head life | 20,000 media contact hours |
| +12 V supply | ± 0.6 V, 900 mA average, 100 mV peak-to-peak ripple |
| +5 V supply | ± 0.25 V, 600 mA average, less than 100 mV peak-to-peak ripple |
| Hard error rate | 1 in 1012 bits |
| Seek error rate | 1 in 106 seeks |
| MTBF / MTTR | 8,000 hours at 25 % duty cycle / 30 minutes |
| Operating temperature | 10 °C to 46 °C |
| Operating humidity | 20 % to 80 %, non-condensing |
All figures are from Tandon's Tables 2-1 to 2-3, pp. 2-2 to 2-4.[1] IBM's own reference for the drive it sold gives some looser figures: 6 ms track to track, 500 ms maximum start time, and ± 5 % on both supplies.[4]
DC power enters on a four-pin AMP connector, J2: pin 1 +12 V, pin 2 +12 V return, pin 3 +5 V return, pin 4 +5 V. A 3/16-inch quick-disconnect lug takes the chassis ground from the controller, and Tandon says the chassis should be earthed for proper operation.[1]
Identifying a TM100-1
[edit | edit source]The single-sided and double-sided drives look the same from outside. Two quick checks:
- On the logic board, a single-sided drive has one head-cable connector (plug 6); a double-sided drive has two (plugs 5 and 6).[5]
- Tandon's spare-parts list gives the head module as 171113-002 "Module SSR" for the single-sided drive and 171113-001 "Module DSR" for the double-sided one.[1] minuszerodegrees notes that a double-sided drive shows "DSR" under the front latch.[2]
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Configuration
[edit | edit source]Drive address and options are set by a programmable shunt (AMP 435704-7) in a DIP socket at location 1E on the logic board. Its positions can be cut, or it can be replaced by a DIP switch. The settings are on pp. 3-5 to 3-8 of Tandon's manual, with the board layout in Figure 3-3.[1]
| Jumper | Function | Setting |
|---|---|---|
| DS0-DS3 | Drive select | Cut all except the one that addresses this drive |
| MX | Multiplex: keeps the drive logic enabled at all times | Single-drive systems only; cut in multi-drive systems |
| HS, HM | Not used | Cut |
| W2, W3 | Write flip-flop set and preset lines | W2 standard |
| W4, W5 | Write-protect switch | W4 standard (write protect enabled) |
| RP1 | Terminator resistor pack | Fitted in the last drive on the cable only |
The IBM PC's floppy cable swaps the drive-select and motor-on lines between its two drive connectors, so both drives are jumpered alike and the cable decides which is A:.[3]
Maintenance
[edit | edit source]Head cleaning
[edit | edit source] | Tandon's manual says: "Do not use cotton swabs, solvents, or otherwise clean the head(s) by hand. Damage to the head(s) may result." Tandon's guidance is that quality media normally keeps the heads clean, and that where contamination is extreme a cleaning diskette may be used according to its maker's instructions (p. 6-1).[1] |
The minuszerodegrees.net author describes a different practice for heavy oxide deposits from disks that shed their coating: a cleaning diskette may need 20 to 50 passes, so he uses isopropyl alcohol on a cotton tip instead, taking care not to damage the heads, and has needed a couple of minutes of work to clear a thick layer. He also warns that cleaning diskettes are abrasive and that a drive cleaned after a bad disk will be fouled again if that disk goes straight back in.[6] That is his practice, not Tandon's.
Head carriage rails
[edit | edit source]Tandon's manual contains no lubrication instruction. The most common fault minuszerodegrees reports is hardened lubricant on the rails the head carriage slides on, so that the carriage moves stiffly or not at all. With the power off, the carriage should slide freely by hand against slight resistance from the stepper motor. The site's author cleans the old lubricant off and re-lubricates with a silicone-based lubricant, grease or spray, which he and others have found satisfactory.[6]
Drive belt
[edit | edit source]The spindle is belt-driven by a DC motor.[1] Tandon's part number for the belt is 914000-001 (Appendix A, p. A-1). To replace it, turn the drive over with the spindle up, remove the old belt, loop the new one shiny side inward onto the small flanged motor pulley, then turn the spindle while working it onto the large spindle pulley (p. 6-7, Figure 6-1).[1]
Track 0 switch
[edit | edit source]The TM100's Track 0 sensor is a mechanical switch, operated by the head carriage between tracks 0 and 3 (p. 4-3).[1] minuszerodegrees quotes Chuck(G) of the VCFed forum: "I've found that many of the 'alignment' issues on Tandon 100s to be not alignment per se, but a dirty track 0 sensor."[6] Check it before touching any alignment.
Alignment and adjustment
[edit | edit source]Tandon's checks need a dual-channel oscilloscope and a certified alignment diskette, Dysan 224/2A or equivalent. The alignment diskette and drive must stabilise at room temperature for one hour first (p. 5-6).[1]
| Check | Tolerance | Adjustment | Manual |
|---|---|---|---|
| Drive motor speed | 300 RPM ± 1.5 %; the 60 Hz ring of the speed disk on the spindle pulley stands still under fluorescent light | R4 on the servo board | pp. 5-3 to 5-5 |
| Radial track alignment | Cat's eye at track 16: smaller lobe not less than 75 % of the larger. Track 16 is 1.9167 in from the hub centre | Head module retaining and cam screws | pp. 5-6 to 5-9 |
| Index to data | 200 ± 100 µs | Index sensor retaining screw | pp. 5-9 to 5-10 |
| Head azimuth | Within ± 18 minutes on the third burst at track 34 | Not adjustable: replace the module assembly | p. 5-11 |
| Track 0 switch and stop | As described | Switch position; stop | pp. 5-12 to 5-13 |
minuszerodegrees adds that the spindle flywheel carries both 50 Hz and 60 Hz strobe rings, so use the one that matches the local mains frequency, and lists two other ways to measure speed: ImageDisk's Test RPM command, or the frequency at pin 2 of the servo board's LM2917.[6]
Media
[edit | edit source]The drive reads and writes single-sided 48 TPI, 40-track disks.[1] In an IBM PC it needs single-sided, double-density, soft-sectored diskettes.[4]
Related pages
[edit | edit source]- Tandon TM100-2
- IBM PC (5150)
- IBM FDD Adapter
- Floppy Drive Repair
- Recommended Tools
- IBM 5-1/4" Diskette Drive Technical Reference
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 Tandon Corporation, OEM Operating and Service Manual, TM100-1, TM100-2 Disk Drives, 48 Tracks Per Inch, part number 179022-001 Rev. B, 1983 (printed 7-83), hosted as File:Tandon TM100-1 TM100-2 48TPI Operating and Service Manuals 1983.pdf.
- ↑ 2.0 2.1 minuszerodegrees.net, "IBM 5150 - Early Versions", section "Floppy Drive" (retrieved 2026-10-01). Very early 5150s had a single-sided TM-100; DOS 1.0 and 1.1 format its disks to 160 KB and DOS 2.0 and later to 180 KB; DOS 1.1 (May 1982) introduced double-sided support; a double-sided drive has "DSR" under the front latch.
- ↑ 3.0 3.1 minuszerodegrees.net, "IBM 5150 - Floppy Drive Support" (retrieved 2026-10-01). IBM's name "160 KB Diskette Drive", the 160 KB and 180 KB formats, BIOS and controller support, and the IBM floppy cable that swaps the drive-select and motor-on lines.
- ↑ 4.0 4.1 IBM, Personal Computer Hardware Reference Library: IBM 5-1/4" Diskette Drive, part number 6361486, p. 3, hosted as File:IBM Options and Adapters - IBM 5.25-inch Diskette Drive.pdf. Mechanical and electrical specifications, including dimensions and weight; logic diagrams for three drive types on pp. 5-12.
- ↑ minuszerodegrees.net, "Tandon TM-100 - Single versus double sided" (annotated photograph), hosted as File:Tandon TM100 single-sided logic board (minuszerodegrees).jpg.
- ↑ 6.0 6.1 6.2 6.3 minuszerodegrees.net, "Tandon TM100-2 in IBM 5150/5155/5160 - Known Problems/Issues" (retrieved 2026-10-01). The site author's own repair notes on the TM100-2; the mechanism is shared with the TM100-1.