Jump to content

Forums

  1. Important Information

    1. The 68kMLA Forum Rules   (9943 visits to this link)

      To quote vintage Apple manuals: "Read Me First!"

  2. Community Connections

    1. General 68kMLA News & Stuff

      What's going down in the barracks.

      3972
      posts
    2. Conquests

      Discuss your latest vintage Mac finds!

      39269
      posts
    3. Trading Post

      Feel free to trade all of your Mac goodies here with all honest intentions. The website provider assumes NO liability, so buyer beware! Please see this topic for more information.

      52468
      posts
  3. Projects & Hosted Forums

    1. RetroChallenge

      What can you do given only one month and strictly "retro" hardware? Find out with RetroChallenge!
      http://retrochallenge.org/

      1484
      posts
    2. 68kMLA Wiki

      The creation and maintenance of the 68kMLA's information repository.
      http://68kmla.org/wiki/

      483
      posts
  4. 68k Model Forums

    1. Compact Mac

      Macintosh, 512k, SE, etc.

      45219
      posts
    2. Mac II, Quadra & Centris

      Just think, having a Quadra 950 in 1992 would be like having a Mac Pro today… except with more slots, more expandability, and on-board SCSI!

      12881
      posts
    3. 68k LC & Performa

      Ah, the consumer computers!

      7887
      posts
    4. 68k PowerBook

      From the Portable to the 190cs.

      9738
      posts
  5. PowerPC Model Forums

    1. NuBus Power Mac, LC & Performa

      The NuBus architecture gets a new brain!

      2636
      posts
    2. PCI Power Mac & Performa

      The PPC comes of age and adopts the industry standard expansion slot.

      5858
      posts
    3. G3/G4/G5 Power Mac, iMac & eMac

      From the Beige G3 to the quad-core G5, via various iMacs!

      13688
      posts
    4. PPC PowerBook & iBook

      All that power in a laptop? Never…

      8951
      posts
  6. Everything Else…

    1. Apple I, ][, /// & Lisa

      Not really 68k Macs, but certainly Vintage!

      7315
      posts
    2. Newton

      The best PDA ever finally gets its own forum!

      1063
      posts
    3. Software

      Includes system stuff, productivity, emulation, design, and games for pre-OS X Macs!

      17350
      posts
    4. Hacks & Development

      Yes, it's back! Hardware hacks/modifications and software development for Mac OS.

      18360
      posts
    5. Peripherals

      Anything you can hook up to your Mac or stuff into it as an interface!

      14439
      posts
  • Posts

    • Kind of you to think of me, but unfortunately I'm nowhere near competent enough at the kind of low-level programming this would require.  Aside from some dilettante dabbling, I'm most comfortable firmly in application space   That said, definitely sign me up for a Linux version (modulo financial disaster).  I'd love to have a go at getting the "split world" stuff going (someone hacked rootless mode into Basilisk a while back, I was wondering if using the same approach but in reverse might work to allow handing over parts of the Mac desktop to the Linux side to draw...)
    • A quick update on this: I've spent quite a lot of time trying to get what I think is the release GEMDOS 1.1 running on this using the DR compiler suite.  Unfortunately it is very crashy, and adding debug output seems to move the crashes around, which is not entirely helpful.  Part of this is about uninitialised memory, but it's quite hard to debug.  I'm considering whether to try to build this using the GCC Atari cross-compiler suite thing for MiNT, which can produce basic TOS executables.  Nothing else is required for building the GEMDOS as far as I can see, but it would mean that this wouldn't be able to be self-hosting any more, which would be a shame.
    • Discharge the CRT before you work at the AB!
    • Are you measuring the 12V rail with or without load? Maybe something is pulling too much current of this rail, causing the voltage drop. I usually disconnect logic board, FBT and the vertical drive circuit, which all feed of the 12V rail, when troubleshooting this scenario.   Also, if you have access to a benchtop power supply, you can inject 12V directly on the analog board (with the Mac disconnected from the mains) and check current draw and troubleshoot the feedback circuit (see below). Like bibilit mentioned, the opto-coupler is usually a prime suspect, and on rare occassions I have also had to change the LM324 op amp.   Here is the feedback circuit that controls the switching transistor:     And the explanation to the above:   The feedback control circuit monitors the +12V supply voltage through a voltage divider comprising R35, R56 and R38. This divided-down voltage is compared with a 6.2V zener diode-derived reference voltage (from R34 and CR19). The system tries to maintain equality of the voltages presented to the input terminals of the op-amp by driving the switching converter more or less hard as necessary. An optoisolator (U3) couples the control circuitry, which is all referenced to digital ground, to the core switching converter, which is referenced to primary ground. Resistor R56 (located just above the speaker) allows fine adjustment of the output voltage. Stability of the feedback system is assured by C21, R37, C27 and C28. If the +12V supply voltage is too low, the LED inside the optoisolator is driven with less than normal current. This, in turn, reduces the current through the optoisolator’s transistor, which ultimately commands the switching core to increase its output. The opposite happens if the supply voltage is too high.    
    • No force at all, hot glue is not strong enough to bother you.
×