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Thread: Couple of questions about 5150

  1. #1
    Join Date
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    Default Couple of questions about 5150

    Hi all,
    Bought an XT on eBay but a 5150 arrived instead (I guess the seller didn't know it was a 5150, the picture was blurry).
    Sold as spares or repairs.
    When I powered it on at work it threw garbage up on the screen ( I didn't have any disks with me, I wasn't expecting it to arrive until tomorrow at the earliest)


    It booted fine with a DOS disk in it when I turned it on at home a few hours later.
    I decided to investigation what the cause of the garbage was as it was supposedly stored in a shed for many decades. I removed a few DIP rams which had filthy contacts and small amounts of corrosion. To cut a long story short does anyone know where I can get a replacement MOSTEK 8225 (MK4116N-3GP) as one of the contacts simply fell off. As well as that does anyone know if dirty contacts will have caused that stuff to appear on the screen in the first place?

  2. #2
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    Dirty or corroded contacts on RAM could be one cause of the problem, but until you get the replacement...
    I'd post a WTB for a couple of 4116's on the board and see if there are any takers.
    patscc

  3. #3
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    Quote Originally Posted by patscc View Post
    Dirty or corroded contacts on RAM could be one cause of the problem, but until you get the replacement...
    I'd post a WTB for a couple of 4116's on the board and see if there are any takers.
    patscc
    Ah I didn't realize that. I thought you had to replace it with the exact same model number chip (still fairly new to all this!). I had trouble finding the "MK4116N-3GP".
    So any 4116 ram chip will do then?

  4. #4
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    Yeah, as long as it's not a slower speed, you should be fine. Most chips can be cross-referenced to parts from other suppliers.
    If you want to get fancy, just "WTB: a couple of 4116's for IBM 5150 16k motherboard", and most people will know what you're talking about.
    patscc

  5. #5

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    Maybe the problem is corrosion on the sockets, before buying anything, take a deep look. By the way, it's pretty easy to find your IC.
    Try to reseat RAM. And please tell what is your board version, should be written near the memory.
    Last edited by lucasdaytona; October 3rd, 2012 at 01:23 PM.

  6. #6

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    I don't think it's necessarily a ram issue but it might be a rom issue. You said that when you booted it without a disk you got the garbage but with a disk it worked ok, right? That sure sounds like a bad rom basic chip. You realize that when that machine doesn't find a bootable disk it defaults to rom to boot basic and that's the scenario you described.
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  7. #7

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    My advice is:

    Remove every card from your system, only leave the video card. Test the computer. Problem? Remove the video card, clean the contacts, put it again, test again, problem? Remove the extra memory chips, leave your board with only 64KB (I think that you can't remove all banks, since bank 0 is soldered), do the necessary jumper/dip changes, test, problem? Post your results here.

    BUT if the system works ok with a boot disk, reseat the ROM chip.

  8. #8
    Join Date
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    Quote Originally Posted by Stone View Post
    That sure sounds like a bad rom basic chip.
    Which on a 5150 motherboard is split over 4 chips: U29 to U32

    Quote Originally Posted by lucasdaytona View Post
    Remove the extra memory chips, leave your board with only 64KB (I think that you can't remove all banks, since bank 0 is soldered), do the necessary jumper/dip changes, test, problem? Post your results here.
    The OP is sure to have the later version of the 5150 motherboard (the 64K-256K one). That contains the 10/27/82 edition of the BIOS, which has bugs that prevent proper operation if less than 4 banks of RAM are present. Details [here]. However, for the purposes of experimentation, it will be fine because something is still shown on screen.

  9. #9
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    If the 5150 motherboard uses 4116 memory chips its the 16-64KB version.
    The 64-256KB motherboard uses 4164 memory chips.

    The best place to pickup replacement chips is ebay. I purchased
    some TMS4116 chips awhile back for a good price. I see lots of MK4116
    and TMS4116 listed, prices average between $1-$2 per chip. I'd suggest
    purchasing some extras....first remove all your existing chips and inspect
    to see if any other leads are broken before ordering.

  10. #10
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    Quote Originally Posted by mikey99 View Post
    If the 5150 motherboard uses 4116 memory chips its the 16-64KB version.
    Shame on me for not picking up on that point.

    Maybe the BIOS was upgraded to the 10/27/82 edition.

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