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Thread: IBM XT 5160 POSTs but won't boot

  1. #11

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    I checked the PSU. It's giving me a steady 12.3v and 5.15v. They don't fluctuate at all during the boot process.

    I've also done some testing with the RAM. I removed bank 3 and powered on. No change. I also removed bank 2. No change. Removed bank 1. No change. Then I removed bank 0 and reinstalled 8x spare 64K chips I had lying around, and 1 of the ones I removed during testing to give the full 9 chips for bank 0. Again, no change.

    I'm guessing my computer was a Friday afternoon special. The RAM all looked as though it was factory installed, but I came across a good 10 or so bent pins that obviously happened during installation. The pins would have still been making contact since the computer was working up until recently, it just looked pretty sloppy.

    Sometimes it does give some slightly different behaviour. On one occasion it seemed to want to read the floppy drive, but the drive made some sort of ratcheting noise. It sounded like the head was trying to move past the end of its travel. I had to power off to get it to stop. Remember, the FDD is confirmed working in another PC. On another occasion, the HDD sounded like it read something, but then the drive LED went out and it didn't do anything more. I can't reproduce this behaviour. It doesn't do the same thing after rebooting.

    Is there some way that I can test the ISA bus? I have a multimeter, but no oscilloscope. The video card seems to work perfectly. Would that indicate a fully working ISA bus?

  2. #12
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,484

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    Quote Originally Posted by seanneko View Post
    I checked the PSU. It's giving me a steady 12.3v and 5.15v. They don't fluctuate at all during the boot process.
    Quote Originally Posted by seanneko View Post
    I have a multimeter, but no oscilloscope.
    A multimeter will not show how 'clean' the voltage is, and so your measurement only provides a certain level of confidence. You did not earlier indicate trying a spare PSU, and so I guess that you do not have one, nor an adapter such as shown at [here].

    Quote Originally Posted by seanneko View Post
    I've also done some testing with the RAM. I removed bank 3 and powered on. No change. I also removed bank 2. No change. Removed bank 1. No change. Then I removed bank 0 and reinstalled 8x spare 64K chips I had lying around, and 1 of the ones I removed during testing to give the full 9 chips for bank 0. Again, no change.
    Imagine some kind of addressing problem. For example, writing to an address actually writes to multiple addresses.

    Quote Originally Posted by seanneko View Post
    Sometimes it does give some slightly different behaviour. On one occasion it seemed to want to read the floppy drive, but the drive made some sort of ratcheting noise. It sounded like the head was trying to move past the end of its travel. I had to power off to get it to stop. Remember, the FDD is confirmed working in another PC. On another occasion, the HDD sounded like it read something, but then the drive LED went out and it didn't do anything more. I can't reproduce this behaviour. It doesn't do the same thing after rebooting.
    Out of curiosity, has this motherboard been affected in the past by a leaking NiCad battery ?

    Quote Originally Posted by seanneko View Post
    The video card seems to work perfectly. Would that indicate a fully working ISA bus?
    No. Different cards utilise different amounts of the ISA bus.

    Because your video card is working, what you have is a certain level of confidence (and only for the slots that the video card has been used in).

    Quote Originally Posted by seanneko View Post
    Is there some way that I can test the ISA bus? I have a multimeter, but no oscilloscope.
    With a multimeter, I think that the best you can do is look at the motherboard schematic, then for each contact in slot 1:
    * Very continuity of that contact to the particular pin of the particular IC that the contact is indicated as being connected to.
    * Very continuity of that contact to the same contact in each of the other slots.

    And if that is all good, all you have is a certain level of confidence.

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