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Macintosh Classic

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The Macintosh Classic was released in 1990 and ran until 1992, though runs the same 8MHz Motorola 68000 found in the earlier Macintosh Plus and Macintosh SE models. Similar to the SE model, the Classic has room for an internal hard disk. The Classic wasn't an overly remarkable computer, but we believe it was designed to be a low cost solution ideally for the education market. As a result, the Macintosh Classic was commonly found in schools during the early to mid 1990s.

Secret ROM Disk

There is an embedded copy of Apple System 6 stored in the ROM. Hold down Command + Option + X + O during power-on to boot off the ROM disk.


  • Due to the age of this computer, modern usage requires the logic board have the capacitors replaced and the PRAM battery removed or replaced. Capacitors on the analog board may also need to be replaced if you experience issues with the display.
  • Another potential Classic issue is the failure to complete the "POST" sequence and the system will stop loading just before the point where the "happy Mac" or blinking disk icon would show up. We suspect this is the result of a defective SCSI bus.


Analog Board Voltage

Some tips on modifying Mac Classic Analog Boards!

If you want to modify a Mac Classic from 110v to 240v (or vice versa) use
these tables:

Late Revision Classic Analog Board (JP2 marked on PCB across CP13 location)

        110v            240v
JP1     Wire Link       -
JP2     -               Wire Link
CP1     220uF 250V      220uF 400V
CP13    220uF 250V      -
CP19    4.7nF 250V      10nF 250V               <-- Must be Class Y Rated
CP38    Wire Link       10nF 250V               <-- Must be Class Y Rated

Early Revision Classic Analog Board (JP2 not marked across CP13)

        110v            240v
JP1     Wire Link       -
CP1     220uF 250V      220uF 400V
CP13    220uF 250V      220uF 400V
CP19    4.7nF 250V      10nF 250V               <-- Must be Class Y Rated
CP38    Wire Link       10nF 250V               <-- Must be Class Y Rated



Capacitor replacement (logic board)

The SMD capacitors on the logic board will most likely have already started leaking electrolyte out the bottom, and failing to replace them in a timely manner will result in further leakage with possible damage to nearby components. See below list of capacitors to replace:

  • 7 x 47uf 16V
  • 1 x 1uf 16V

Capacitor replacement (analog/PSU board)

This list is every radial capacitor on the Classic's analog/PSU board. You don't necessarily need to replace all of these, but it's probably more convenient all at once.

  • 2 x 220uf 250v
  • 3 x 470uf 25v
  • 4 x 1uf 50v
  • 1 x 1000uf 10v
  • 2 x 2200uf 10v
  • 1 x 2200uf 16v
  • 1 x 470uf 50v
  • 2 x 47uf 25v
  • 1 x 220uf 16v
  • 1 x 470uf 10v
  • 1 x 1000uf 16v
  • 1 x 47uf 16v
  • 1 x 10uf 25v
  • 1 x 1000uf 25v
  • 1 x 220uf 50v
  • 1 x 4.7uf 250v

External Resources

See Also