Mac LC II Memory Issue

Discussion in 'Apple Collectors' started by macintoshmartin, Sep 29, 2012.

  1. macintoshmartin macrumors newbie

    macintoshmartin

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    #1
    So I've recently installed 2 4MB SIMMs in my LC (which has System 7.5.3), and when I go to power on the computer, it gets stuck at the welcome to macintosh screen. I've tried to disable extensions but that didn't work, but when I tried to boot off of a 6.0.8 Disk Tools floppy it booted all the way and I was able to see I had 10 MB installed. So then I made 7.0.1 Disk Tools floppy thinking it was my hard disk installation having a problem but that also gets stuck on the welcome to macintosh screen, and when I remove the new RAM it boots fine. Anyone have any idea why this is happening? :confused:
     
  2. havokalien macrumors 6502a

    havokalien

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    #2
    Two possibles

    Bad/too slow of ram or failing caps on the motherboard. I would lean towards th caps. I know you saw the ram off a boot disk but when it try's to read the hard drive my SE 30 is doing the same thing.
     
  3. macintoshmartin thread starter macrumors newbie

    macintoshmartin

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    #3
    The thing is that I've copied the system folder from the boot disk to the hard drive and it worked so I've pretty much ruled out hardware problems.
     
  4. MacTech68 macrumors 68000

    MacTech68

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    #4
    How many chips are there on each 4MB module?

    If there's 8 (or 9) you should be fine.

    If there's 4 and a single square chip, YMMV. These are bank switching SIMMS and some don't play well with Macs.

    A nice clear pic of the modules, showing the numbers on the chips might help. :)
     
  5. macintoshmartin, Sep 30, 2012
    Last edited: Oct 1, 2012

    macintoshmartin thread starter macrumors newbie

    macintoshmartin

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    #5
    Right now I can't take any pictures of the ram but I can tell you that they're 30 pin parity SIMMs, one that's 80 ns and the other is 70 ns, and they both have 9 separate chips on them.

    EDIT:
    Added a picture of the RAM, It's a bit bad quality but I think you can see them pretty ok. The chips read M5M44100J 121SG7C-8, and they have the Mitsubishi logo on them.
     

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  6. MacTech68, Oct 2, 2012
    Last edited: Oct 2, 2012

    MacTech68 macrumors 68000

    MacTech68

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    #6
    Well, they appear to be 5V FPM which is a good start. Speed is more than adequate.

    However, without other similar sized memory to test, I may have to agree with havokalien's comment about leaking SMD caps. The problem may even be etched tracks (though it shouldn't pass POST).

    It's possible that the ones circled below are the culprits.
     

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  7. macintoshmartin thread starter macrumors newbie

    macintoshmartin

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    #7
    Ok, so I've looked into the capacitors and I think all of them are fine. I can't test them with a voltmeter now but none of them are leaking and I don't see any corrosion on the logic board. But I have to ask, what changed between System 6 and System 7, because the earlier one works while the newer one gets stuck on the start-up screen?
     
  8. gkarris macrumors 604

    gkarris

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    #8
    If I remember correctly, some System 7 versions require an Enabler to work with newer (at the time) or certain Macs...

    If not in this case, then make sure the Memory SIMMS are rated with the proper speed for that Mac.
     
  9. MacTech68 macrumors 68000

    MacTech68

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    #9
    It's possible that the System 6 Disk Tools disc is (by design) missing certain system resources such that the area of memory affected isn't accessed.

    It could be faulty RAM.

    BTW, I'm assuming the 7.0.1 Disk Tools is a copy of an Apple disk?

    System enablers didn't become an issue until the LCIII and And System 7.1
     

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