Resolved PowerBook G4 17" power button “dome cover over LED”?

Discussion in 'PowerPC Macs' started by B S Magnet, May 4, 2019.

  1. B S Magnet macrumors 6502

    B S Magnet

    Dec 5, 2018
    don’t read my status message
    After some moderate searching, I’ve drawn blanks and would love some insight from the Club 17 crew.

    I went ahead and cleaned away the original garbage thermal paste and thermal pad on my A1139 to throw on some new, much better paste. [This all went without a hitch, but oh my lordt, the state of what I had to clean out was breathtakingly gross and disintegrated. Pics of the before/after by request.] :)

    What prompted this thread question is a step in iFixit’s disassembly guide for reaching the heat sink, specifically Step 28.

    This was the moment when I noticed how there’s an LED on the logic board and a plastic, dome-shaped cover described as a “lens” which needed to be gently removed on the A1139 to access the Torx screw partly covered by it (this step for earlier PowerBook 17" models is slightly different and doesn’t require dome cover removal).

    Whatever the case, cue my genuine surprise. I’ve never seen the power button illuminate on this PowerBook under any condition (i.e., powering on/off, putting the system to sleep, etc.). On 15" aluminium models (A1138 and prior), this area is described solely as an ambient light sensor, not an LED. On the 15" models, it doesn’t appear to be a dome.

    Are there special conditions wherein the 17" power button is designed to illuminate, or was this a latent feature that was left unimplemented? Or, more likely, is it that iFixit’s description of “LED” here is erroneous and merely one of the solid state ambient light sensors?
  2. CooperBox macrumors 65816


    Nov 28, 2010
    France - between Ricard & Absinthe
    I believe this is just a misuse of the term 'power button LED window.' Looks like an ambient light sensor.
    Just checked the PBook Medic tear-down video to double-check, but there's no mention in the commentary other than "Speaker assy".
  3. Totalbearface macrumors member


    Apr 19, 2019
    United Kingdom
    It’s an ambient light sensor. There’s one on each side. When you’re using your PowerBook, put your hand over the speaker grille near its general location and you’ll notice the screen dim and keyboard illuminate.
  4. B S Magnet thread starter macrumors 6502

    B S Magnet

    Dec 5, 2018
    don’t read my status message
    Thanks. I understand how the ambient light sensors work.

    Until this disassembly, I had presumed, however incorrectly, that the ambient light sensor for the right side was under the speaker grille more generally — not directly beneath the power button specifically.
    --- Post Merged, May 4, 2019 ---
    I think you’re correct. For a hot minute, I was thinking this was some kind of unimplemented feature, vis-à-vis how the power button itself used to pulsate on the Power Mac G4s.

    I mean, for anyone who’s looked inside a DLSD PowerBook, there are a mess of indicators scattered throughout which hint that Apple’s product teams were looking beyond the DLSD series introduction with subsequent revs prior to the 7 June 2005 Jobs-Intel announcement — stuff like flat-wire parts labelled “For PowerBook G4 1.67 or later”; the long-storied intention to use the PPC7448 processor; and that thread from a while back which hinted at an Apple supplier labelling DDR2 SO-DIMMs "for PowerBook G4/G5”.
  5. ScreenSavers macrumors 6502


    Feb 26, 2016
    Bloomingdale, GA
    There are usually light sensors on either side of the keyboard on the late PowerBooks and the non-unibody MacBook Pros.

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