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Thread: IBM 5150 help!

  1. #1

    Default IBM 5150 help!

    Hello all,

    I recently acquired a 5150 that doesn't work properly. The computer switches on and starts POST however the computer hangs at the blinking cursor and doesn’t move on to boot from floppy or display any error codes on the display. Not entirely sure where to start. The voltages for the power supply have been checked and are all fine and stable. Capacitor had gone but was replaced. Video card seems to be working. It’s a 64 to 256 ram board with all 4 banks population. Bizarrely one chip is an apple ram chip.

    Any suggestions?

    Kind regards,
    Max

  2. #2

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    Check to be sure that the floppy or floppies are properly configured in the switch bank on the motherboard.
    PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

  3. #3
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    How long are you waiting before giving up on post? The 5150 takes a lot longer than you'd expect to do the RAM test and get ot the end of post. Something like 20 - 30 seconds or so of just a flashing cursor, which feels like forever if you are used to modern computers.

    IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
    IBM PCJr Model 48360 640kb RAM, NEC V20,, jrIDE Side Cart, 360kb Floppy drives running MS-DOS 5.00
    Evergreen Am5x86-133 64Mb Ram, 8gb HDD, SB16 in a modified ATX case running IBM PC-DOS 7.10

  4. #4

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    Hi all,

    Thanks for your help. I have one floppy drive and one fixed disk drive and their relevant adapter. I do believe they are configured in line with the switches in switch 1 for 1 floppy drive and requesting the computer to boot from the floppy drive after POST.

    I have waited up to 5 minutes and the computer won’t move off the flashing cursor. So I believe it should have moved off by then. I know the 5160 tests RAM in 24K chunks or so and I believe this 5150 has 640K inside it.

    Would having the RAM switch configured incorrectly cause a halt in POST?

    Kind regards,
    Max

  5. #5

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    It wouldn't hurt to check that all the switches are correctly set.

    Try removing the RAM expansion card and see if that makes any difference.
    PM me if you're looking for 3½" or 5¼" floppy disks. EMail “ ” For everything else, Take Another Step

  6. #6
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    If you try the procedure at [here], do you hear the expected series of beeps (1 long, 2 short) ?

    Quote Originally Posted by Max1227 View Post
    The computer switches on and starts POST however the computer hangs at the blinking cursor and doesn’t move on to boot from floppy or display any error codes on the display.
    I have seen a similar symptom in the IBM 5160, but not the IBM 5150. For the 5160, the two known causes are shown in the second table row at [here]. I cannot replicate the first of the two causes in the 5150 (in the 5150, there is no video at all). The second cause though, is something expected for both the 5150 and 5160. So, perhaps try your video card in a different slot, and perhaps clean the edge connector on the video card.

    Quote Originally Posted by Max1227 View Post
    Bizarrely one chip is an apple ram chip.
    If it is a 4164-class chip (i.e. what is required of the 64KB-256KB motherboard), it is not expected to be a problem.

    Quote Originally Posted by Max1227 View Post
    Would having the RAM switch configured incorrectly cause a halt in POST?
    Not that I am aware of.

  7. #7
    Join Date
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    Quote Originally Posted by lutiana View Post
    How long are you waiting before giving up on post? The 5150 takes a lot longer than you'd expect to do the RAM test and get ot the end of post. Something like 20 - 30 seconds or so of just a flashing cursor, which feels like forever if you are used to modern computers.
    Quote Originally Posted by Max1227 View Post
    I have waited up to 5 minutes and the computer won’t move off the flashing cursor. So I believe it should have moved off by then.
    Some factual timings, using my IBM 5150's, with the keyboard removed:

    256 KB conventional RAM in total: 301 error displayed about 25 seconds after power-on.
    640 KB conventional RAM in total: 301 error displayed about 50 seconds after power-on.

    In both cases, there was a single beep from the speaker (signaling end-of-POST) about 5 seconds later.

  8. #8

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    Sorry about slow response! Some things to add:

    1. I did remove the RAM card and reconfigure the switches but same results.
    2. I did reseat the graphics card and no change unfortunately and move it’s slot.
    3. I don’t hear any beeps - the computer just flashes the cursor endlessly and doesn’t beep or do anything.

    Interestingly with no keyboard attached I know most IBM systems would show a 301 error but this one doesn’t. It just flashes the cursor endlessly.

    Is it possible that the BIOS chip is damaged so it cannot complete POST and it halts the CPU?

    Kind regards,
    Max

  9. #9

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    Just a thought: It might be worth as a quick test confirming the DIP switches that are ON do have actual continuity on the meter. I have found of late a number of old DIP switches that are open circuit in the ON position due to oxidation of the contacts, so its worth checking them at least once, just in case. Also, if that is the case, exercising them and/or cleaning them doesn't help much and they require replacing.

  10. #10
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    Burn a Supersoft diagnostics chip and see what you get. If the machine has more than one problem, it's going to be a bear zeroing in on it otherwise.

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