DuoDisk
Two Disk II-class drives in one beige case; the left one is drive 1. Not for the IIc.
Open the DuoDisk in Retro Bench- Also
- DuoDisk 5.25 A9M0108: two half-height drives on one analog card (676-11101, 676-11102 or 676-11107), round cable 590-0114 (DB-25 at the drive, DB-19 at the card), DuoDisk controller card = UniDisk / Apple 5.25 Drive controller card
- Year
- 1983
- CPU
- none (dumb drive)
- ROM
- On the controller card: P5 341-0027 boot PROM and P6 341-0028 sequencer PROM (Disk II circuit)
- OS
- DOS 3.3 / ProDOS
Chips
| Chip | Where | Role |
|---|---|---|
| MC3470 floppy disk read amplifier | C1 on the DuoDisk analog card | Read amplifier, peak detector and pulse shaper |
| 74LS125 quad 3-state buffer | B3 (cards 676-11101/11102) or C3 (676-11107) on the analog card | Drive-side 3-state gates: write protect, read data, write data, write request |
| CA3141E high-voltage diode array | B1 on DuoDisk analog cards 676-11101 and 676-11102 (Apple 352-3141) | Diode array in the DuoDisk read/write head switching |
| P6 state-sequencer PROM 341-0028 (256 × 8, 6309 type) | PROM P6 on the 5.25 controller card | Logic state sequencer program (the "state machine") |
| P5 boot PROM 341-0027 (256 × 8, 6309 type) | PROM P5 on the 5.25 controller card | Controller boot code at $Cn00-$CnFF |
| 74LS323 8-bit universal shift/storage register | 74LS323 on the 5.25 controller card | Controller data register (shifts disk bits in and out) |
| 74LS259 8-bit addressable latch (9334) | 74LS259 on the 5.25 controller card | Controller soft switches $C080-$C08F,X: phases, motor, drive select, Q6, Q7 |
| 74LS174 hex D flip-flop | 74LS174 on the 5.25 controller card | Sequencer state latch and read-pulse synchronizer |
Ports and connectors
- DuoDisk rear connector (DB-25), DB-25 socket on the DuoDisk back panel
- Controller card DB-19 (back-panel plate), DB-19 socket on the controller card's ribbon, fixed in a back-panel opening
Power rails
| Rail | Expect | Measure at |
|---|---|---|
| +5 V | +5 V | duo-db25 pins 7, 24 (duo-db19 pins 6, 16) |
| +12 V | +12 V nominal UNVERIFIED | duo-db25 pins 19, 20 (duo-db19 pins 7, 8) |
| -12 V | -12 V UNVERIFIED | duo-db25 pin 23 (duo-db19 pin 5) |
Symptoms
- No motor sound at boot
- Motor and LED on, but disk will not boot: check 3141, 74LS125, 3470
- Reads but does not write: check 3141, 74LS125
- Disk data destroyed on Open-Apple-Control-Reset or by some copy protection
- Fuzz or burned parts on the analog card: check 74LS125
- Intermittent faults on early units
- Speed out / disks unreadable elsewhere