Apple Disk IIc
| Apple Disk IIc | |
|---|---|
 |
|
| Disk IIc (All About Apple museum) | |
| Manufacturer | Apple Computer, Inc. |
| Type | External 5.25-inch floppy disk drive |
| Release date | 1984[1] |
| Price | US$329[1] |
| Interface | DB-19 cable to the Apple IIc external disk port |
| Compatible | Apple IIc; also the Apple IIGS disk port, as the last drive in a chain |
| Media | Single-sided 5.25-inch disks |
The Apple Disk IIc is the external 5.25-inch floppy disk drive Apple made to match the Apple IIc, which Apple's service manuals also call the IIc External Drive.[2] It plugs into the IIc's external disk port and appears to software as slot 6, drive 2, the second drive alongside the IIc's built-in one.[3] Wikipedia dates it to 1984 and gives a price of US$329.[1]
Inside, the Disk IIc uses the same drive mechanism (661-0264) and analog board (661-0265) as the Apple IIc's internal drive.[2][4] It has no daisy-chain port, so on a machine that chains drives it must be the last drive.[5]
Connecting
[edit | edit source]The IIc external disk port is a DB-19 connector:[6]
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1-4 | Ground | 11-14 | SEEKPH0 to SEEKPH3 |
| 5 | −12 V | 15 | /WRREQ |
| 6 | +5 V | 16 | Not connected |
| 7, 8 | +12 V | 17 | /DR2 |
| 9 | /EXTINT | 18 | RDDATA |
| 10 | WRPROT | 19 | WRDATA |
Pin 5 is −12 V in Apple's 1983 note on the port.[3] Apple's article carries the caution that connecting anything other than a Disk IIc to the port may invalidate the warranty.[6]
The IIc port and an Apple IIe disk controller card are not wired the same way. Apple's 1983 note says the IIc drive cannot be run from a IIe controller card through a plain ribbon cable from the card's 20-pin header to a DB-19, because pins 9 and 16 of the DB-19 must be left unconnected and pin 19 must go to pin 20 of the card. A IIe drive used on a IIc needs DB-19 pin 10 connected to the drive's pin 20, with DB-19 pin 9 and the drive's pin 19 left unconnected.[3]
On an original Apple IIc the external drive is started with PR#7. IIc logic boards with ROMs that support the UniDisk 3.5 dropped that feature: PR#7 then reports "AppleTalk Offline", and only a UniDisk 3.5 can be started from, with PR#5.[7] Apple's support article on the ROM upgrade gives the same PR#7 test: an Apple IIc that answers "AppleTalk Offline" has the new ROM, and one that tries to start an external drive or reports "Check Disk Drive" has the old one. IIc computers with serial numbers below F6051GFA2S4000 needed the upgrade for the UniDisk 3.5.[8]
On the Apple IIc Plus, the first external 5.25-inch drive is slot 6, drive 1, started with PR#6.[9]
Take-apart
[edit | edit source]Apple's tool is a #2 Phillips screwdriver.[2]
- Case: turn the drive upside down and remove the eight Phillips screws. Hold the case together, turn it over, lift off the top cover and slip the cable out of the slot at the back of the case bottom. When refitting, route the cable behind the drive and seat its grommet in the cut-out.
- Analog card: remove the four screws (two each side) holding the drive shield, unplug the drive cable and lift the shield off. Disconnect the motor cable (J2), the read/write head cable (J3, freeing its wire from the clips) and the LED cable (J4), remove the mounting screw, tilt the rear edge of the card up and slide it out.
- When refitting the card, slide its front edge under the two plastic posts inside the bezel so that the alignment tab comes through its hole. The head cable has four wires on a five-pin connector; make sure each wire meets a pin. Fit the motor connector with its single-wire end towards the rear, and the LED connector with its wires towards the bottom.
- Refit the shield with the ground clip at the right rear, and refit the drive cable with its two unused positions at the front of the connector.
- Bezel, door and spring: with the shield off, remove the four bezel screws (two each side), push the door inwards to open it and hold the spring as the bezel comes away, because the spring is loose.[2]
A mechanism sent to Apple for exchange had to go with its drive shield fitted and the LED cable removed.[2]
Adjustment and maintenance
[edit | edit source]Drive speed is set at VR1 on the circuit board, reached from underneath with the case removed. Apple's procedure runs the Drive Speed test of the 5.25-Inch Floppy Drive Test on an Apple IIc, with the drive lying flat. Turn VR1 very slowly until the indicator is in the "good" range as close to 0 as possible, let the test run for 30 seconds and repeat it. A drive that will not adjust needs a new mechanical assembly.[2]
Apple's preventive maintenance is the same as for its other 5.25-inch drives: clean the read/write head and guide rails with isopropyl alcohol (80 % alcohol, 20 % water) and no grease whenever the drive is serviced, replace a worn or dirty head load button, and check the drive belt for cracks, slippage and lost elasticity.[2] On the Disk IIc the new load button goes through the hole in the shield plate into the head load arm.[2] The steps are given in full on Apple 5.25 Drive.
Apple's Disk IIc service section has no troubleshooting chart. Apple's flowchart for the Apple 5.25 Drive covers the same modules: on a known-good Apple IIc, a motor that does not run points to the cable, analog board and mechanism in that order; a dead "in use" light to the LED and analog board; and a drive that runs but reads wrongly to the cable, the DSPEED adjustment, the analog board and the mechanism.[10]
Parts
[edit | edit source]| Item | Part number | Description |
|---|---|---|
| 1 | 655-5006 | Top case assembly, External Drive IIc |
| 2 | U815-0064 | Load button |
| 3 | 805-5038 | Upper head shield plate |
| 4 | 661-0265 | Apple IIc analog board |
| 5 | 590-0221 | Disk IIc LED cable |
| 6 | 655-5007 | Bottom case assembly, External Drive IIc |
| 7 | 865-0021 | Bumper foot |
| 8 | 815-0836 | Disk IIc LED lens |
| 9 | 655-5005 | Label, External Disk Drive IIc |
| 10 | U880-0002 | Disk drive belt |
| 11 | 815-0811 / 815-0587 | Disk drive door (latch): beige / platinum |
| 12 | 815-0810 | Disk drive bezel |
| 13 | 870-0023 | Spring |
| 14 | 661-0264 | Apple IIc drive mechanism |
| 15 | 590-0212 | Disk IIc cable |
| 16 | 805-0756 | Disk IIc top shield |
Documentation
[edit | edit source]- Apple Disk IIc Technical Procedures: Apple's service section, with take-apart, DSPEED, preventive maintenance and the parts list.[2]
- Apple IIc Technical Procedures: the IIc's own service section, including the internal drive.[4]
Related pages
[edit | edit source]References
[edit | edit source]- ↑ 1.0 1.1 1.2 Wikipedia, "Disk II", section "Disk IIc", retrieved 2026-10-04. Source for the 1984 introduction and the US$329 price.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 Apple Computer, Disk IIc Technical Procedures, from Apple Service Technical Procedures: Apple II Family, Volume Two (072-0229, 1991), hosted as File:Apple Disk IIc Technical Procedures.pdf and described at Apple Disk IIc Technical Procedures. Take-Apart pp. 1.3-1.10 (case, analog card, mechanical assembly, bezel, door and spring, LED cable); Adjustments pp. 2.2-2.3 (DSPEED at VR1); Preventive Maintenance pp. 3.2-3.4; Illustrated Parts List p. 4.3. The main contents page calls the section "Disk IIc (IIc External Drive)".
- ↑ 3.0 3.1 3.2 Apple Computer, "Apple //c External Disk", 9 March 1983, archive.org item Apple_IIc_External_Disk-1983-03-09 (retrieved 2026-10-04). Source for the port carrying the signals of drive two of an Apple IIe disk controller card, access as slot 6 drive 2, and the wiring differences between the IIc and IIe connections.
- ↑ 4.0 4.1 Apple Computer, Apple IIc Technical Procedures, Illustrated Parts List IPL.3, items 10 and 11 (PDF p. 86), hosted as File:Apple IIc Technical Procedures.pdf and described at Apple IIc Technical Procedures.
- ↑ Apple Computer, Apple 5.25 Drive Owner's Guide (1986), Appendix A, "Daisy-chain drive combinations", printed p. 16 (PDF p. 22), hosted as File:Apple 5.25 Drive Owners Guide 1986.pdf: the IIc External Drive and the DuoDisk must be last in an Apple IIGS chain because neither has a daisy-chain port, and the IIc External Drive counts among the 5.25-inch drives allowed in the chain.
- ↑ 6.0 6.1 6.2 Apple Computer, "Apple IIc: Pinouts for External Disk Port", Tech Info Library article 206, revised 23 October 1984, archive.org item IIc_Pinouts_for_Ext_Disk_Port (retrieved 2026-10-04).
- ↑ Apple Computer, "Apple IIc External Drive: PR#7 Can't Boot", Tech Info Library article 1679, created 23 January 1986, reviewed 17 July 1992, in the archive.org collection Apple's Technical Information Library Articles, https://archive.org/details/APPLE_TIL_ARTICLES, file TIL00001_to_TIL60496.zip.
- ↑ Apple Computer, "Apple IIc: How to Determine If It Needs ROM Upgrade for UniDisk", Tech Info Library article 10098, created 14 April 1992, archive.org item IIc_ROM_Upgrade_for_UniDisk (retrieved 2026-10-04).
- ↑ Apple Computer, "Apple IIc Plus: External Drive Configurations", Tech Info Library article 3435, reviewed 8 November 1988, APPLE_TIL_ARTICLES collection (archive.org), file TIL00001_to_TIL60496.zip.
- ↑ Apple Computer, Apple 5.25 Drive / UniDisk Technical Procedures, Troubleshooting p. 4.3, hosted as File:Apple 5.25 Drive and UniDisk Technical Procedures.pdf.