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Apple III

Apple's professional flop (1980): a higher-clocked 6502, the SOS OS, an Apple II compatibility mode. Famous for its thermal reliability problems (no fan → chips "walking" out of their sockets). Typical repair: reseat the chips, recap, PSU.

Identification

  • CPU: 6502B @ ~1.4–1.8 MHz; up to 256 KB RAM; a real-time clock (often dead).
  • Video: 80-column text + graphics; composite/RGB output.
  • Media: Disk III drive (built-in) + ProFile hard disk (via interface); Apple III+ = revision.

Repair (technician)

The Apple III's curse: chips creeping out of their sockets

With no ventilation, thermal cycling made the ICs rise out of their sockets (intermittent contacts). The real fix: firmly reseat every socketed chip, and resolder/replace oxidized sockets. (The "lift the machine and drop it" legend = a symptom of the same problem, not a real repair.)

  • Recap (PSU + board) → Recap; mains-filter RIFA.
  • Dead real-time clock: period part → bypass/replace.
  • PSU: classic service (caps, regulation).
  • Disk III drive: mechanism → clean / emulator.

Modernisation & mods — what to buy, how

The 'chips creep out' myth: re-seat + turned-pin sockets

The Apple III is famous for ICs working loose from their sockets (thermal cycling) → re-seat the chips (the notorious "drop the machine a few cm") and, above all, replace the sockets with quality turned-pin ones. Preventive recap.

  • Storage: Floppy Emu (BMOW) 🟢 handles the Disk III (SD card); ProFile hard-disk emulators 🟡 to drop the mechanical drive.
  • Video: composite output 🟢 → modern display via an upscaler; RGB if present.

⚠️ Do not host ROMs/SOS — method only.

See also

Sources & attribution

Review & corrections

How this space is used

Spotted a wrong value, an outdated procedure, a chip reference that does not match your board? Say so here, with what you observed (model, board revision, serial number, measurement). Every report is cross-checked against a source before anything changes — an unverifiable correction is published as “reported by …, not cross-checked” rather than silently applied.

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