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Compaq Portable II

Computers in Collection

Compaq Portable II, serial …, {#…}

Power supply C13 lost its top, is a charcoal briquette, needs replacement. Justin reports that the system worked well until the power suppy went up in smoke… Circuit traced and this capacitor is the input filter capacitor for the 7905 and 7912 regulators. Replaced with 10uF 25VDC tantalum (Digi-Key 478-1841-ND, AVX TAP106K025SCS). Rated voltage might be a bit under-sized, but I should scope the signal and verify.

Hard drive appears functional, but can’t be used until Compaq setup/diagnostic floppy can be run on the machine to configure CMOS/BIOS.

Power Supply


Assy No. 000552-001 Fab No. 000554-001 REV. B Assy. Rev. “Rev. D” Diag No. 000553 Serial No. “M08E00531”


  • C1, C2: 330uF (M), 250V, 105C, electrolytic, radial leads, 11mm spacing, 25.5mm diameter, 35.5mm height, Nippon Chemi-Con, “KM”, “8723”
  • C6: 5700uF, 6.3VDC, 105C, electrolytic, radial leads, 8mm spacing, 22.5mm diameter, 55.5mm height, Sprague, “676D”, “8726L 2202”
  • C7: 1700uF, 0-20VDC, 105C?, electrolytic, radial leads, 3 terminal, Sprague?, “USA870?H”
  • C8: 410uF, 0-25VDC, 105C, electrolytic, radial leads, 5mm spacing, 12.5mm diameter, 27.5mm height, Sprague?, “672DX”, 8712H (2)USA”
  • C10, C11, C15; 470uF, 25V, (M) 105C, electrolytic, radial leads, 5mm spacing, 12.5mm diameter, 43.5mm height, Nippon Chemi-Con?, “Rx”, 8707(2)”
  • C12, C14, C19: “156” “+25 K”, tantalum
  • C13: ?
  • CR5: Motorola MBR3035PT, “8718 K”
  • CR6: UES1402, “U”, “8720”
  • HY1: FDK HY4722…, “104019-…”, “REV B 87…”, “JAPAN”
  • HY2: Tadiran 101128E-002. “26-87”, “Israel”
  • Q1: Philips BUW13A-S “F8714”
  • Q2: Philips 104021-001, “F8701”
  • U1, U2: “TFK 722” “CNY 65”, “0883”
  • U6: Fairchild uA7905, “8651 Korea”
  • U7: National LM7912CT, “8716”

20181116 Replaced all power supply electrolytic capacitors except C7. System now doesn’t flicker and periodically reboot. However, ambient temperature was significantly lower, so a thermal issue may still exist.

20181230 Cleaned key caps, keyboard case halves, system outer shell. Lubricated key stems. Scrubbed keyboard PCB and switch housing template. Replaced 3(?) capacitive foam plugs with some from Tex-Elec – later tested to be a bit too tall and caused those keys to be inoperative (stuck “on”).

20190101 Cleaned and lubricated floppy drive. Replaced CMOS battery with Tadiran (TL-2201?) I had laying around for 10+ years – 3.6V lithium inorganic size-AA battery.