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Thread: WTB: 87 LMs

  1. #21
    Hybrid booster Turbo Mopar Contributor
    Join Date
    Mar 2007
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    Michigan
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    385

    Re: WTB: 87 LMs

    Just a quick update. I re-installed my "dead" '87 LM last night to try to do a little diagnosis. I plugged it in and it was still dead, checked the pins, made sure everything was connected, still dead...

    ...knocked on it 3 times and it came back to life. (not even exaggerating) Sheesh!

    So, don't throw out any bad LMs. They may be repairable.

  2. #22
    Hybrid booster Turbo Mopar Contributor 85lebaront2's Avatar
    Join Date
    Dec 2005
    Location
    Exmore, Va. USA
    Posts
    513

    Re: WTB: 87 LMs

    Give it a good bash huh? Sounds like the radios.

  3. #23
    turbo addict
    Join Date
    Mar 2014
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    Toronto Canada
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    1,772

    Re: WTB: 87 LMs

    has it still got the plastic sheet between the pcb and case??

    if not ..I bet ..it's shorting inside the case enclosure

  4. #24
    Supporting Member Turbo Mopar Contributor
    Join Date
    Feb 2015
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    toronto
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    1,765

    Re: WTB: 87 LMs

    Quote Originally Posted by Turbo SOB View Post
    Here I am eatin' crow again.

    There's some pretty major differences between the '86 and the '87 TII style LMs, specifically in the EPROM area. The '86 has 2x 8k EPROMs and the '87 TII has 1x 16k EPROM and an EF6840 "programmable timer module". I have no idea what the timer module would do in an '87 that it wouldn't need to do in any other LM, but there it is, with some significant trace routing differences to accompany it. I did find a spec sheet for it, though the only place to find replacements is eBay. I guess one thing to try is to remove it and see if the '87 LM still works.

    Either way, I think my first priority should be to try to repair the dead '87 TII LM. If I can figure out what's wrong with it maybe others can benefit.
    According to my reading Rob L. mentions that it is used in creating PWM.
    Perhaps the comment is in this thread
    https://www.turbododge.com/threads/1984-1986-turbo-logic-module-information.662914/
    I have real 6840 in my chip inventory if you are in a bind. LMK
    Regards,
    Miles

    DD '87 Sundance T1, SLH with rear disks
    '87 CSX #432 2.5 CB TII, SLH

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