I have a PAL Apple IIe, put in service in 1982. Components C9, C12, C15, and C17 on the 820-0073-B motherboard are burnt out. I originally thought they appear to be power diodes, but seem to be 10 µF electrolytic capacitors. I replaced all four and the computer boots properly now.

Starting up, however, the mainboard fails to detect the Z80 card, mouse card and the 64K extension card. The dual drive card in slot 6 works. Does anyone know the exact values of the capacitors? What else could be defective?

  • 3
    C9, C12, C15 and C17 are in fact 10µF, 6V electrolytic capacitors, so your replacement seems to be correct. The exchanged components are all part of the most basic power generation circuitry. Based on your provided information, there is little chance to provide more information. Did you check the basics (power rails for +5V, -5V, +12V, -12V)? Are the cards that are not detected known good cards?
    – tofro
    Nov 7, 2023 at 11:25
  • Thank you very much for your support. The voltages on the power supply unit are OK. The mouse card is now also working. The green "Card ON" LED on the Z80 card is not lit. Do I have to activate this card somehow?
    – Jochen
    Nov 8, 2023 at 10:10
  • The Z80 card won't do anything until you try to boot CP/M
    – tofro
    Nov 8, 2023 at 10:27
  • I booted CP/M plus Master and the Utilities Disk. Nothing happens. Probably the program does not find the Z80 card. I have the Z80 card in slot 3, a tool that shows me the slot configuration reports "empty" for slot 3. This tool does not recognize the Z80 card either. So the card is probably defective?
    – Jochen
    Nov 9, 2023 at 13:03


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