Image Map Image Map
Page 1 of 3 123 LastLast
Results 1 to 10 of 29

Thread: IBM 5160 - Troubleshooting power issues

  1. #1
    Join Date
    May 2020
    Location
    United Kingdom
    Posts
    17

    Default IBM 5160 - Troubleshooting power issues

    Hi all,

    I have an IBM 5160 (256K) with dual floppy drives. I attempted to power it on today, the PSU powered up for a split second, there was a small pop and the magic smoke was released and the PSU fan stopped spinning. Now whenever I try to power it on nothing happens - The PSU fan does not spin.

    I've been following the troubleshooting guide at http://www.minuszerodegrees.net/5150...ems_issues.htm and have removed the tantalum capacitors C56, C58 and C68 (C56 and C58 were clearly blown). I've just removed them and have left their slots empty without anything soldered in to their place - I assume this is correct?

    I've tested for shorts on the motherboard's P8 and P9 rails and as far as I can tell they all look fine - No obvious shorts. This is leading me to believe that the PSU may be to blame. Is there a way to test the PSU standalone? This machine is dual floppy so I don't have an MFM drive to hand to act as load.

    Thanks in advance!

  2. #2
    Join Date
    May 2020
    Location
    United Kingdom
    Posts
    17

    Default

    So I've tried connecting an MFM drive that I took out of a Compaq Deskpro to the PSU in isolation and it still itsn't working - I'm assuming the PSU has issues. I'm waiting for the driver bit so that I can disassemble the PSU - Does anyone have a list of capacitors required for the stock 130W PSU?

  3. #3
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,645

    Default

    It sounds like:
    1. You navigated through the [procedure] and ended up at the page at [here].
    2. Then, per there, you removed C56 and C58.
    3. Then, you reattached P8 from the PSU to the motherboard.
    4. Then you discovered that the PSU still does not fire up.

    Is that case?

    Quote Originally Posted by BakaOsaka View Post
    I assume this is correct?.
    Per the web page pointed to earlier, C56 and C58 are not critical to the operation of this motherboard. Normally, if they are faulty, they can be removed, and the IBM 5160 will start. But there can be exceptions.

    Is the PSU the stock IBM one, or is it a clone ? For example, if a clone PSU, maybe that PSU requires a small load on one (or both) of the 12V lines, and C56 and C58 were providing that small start-up load. Just a guess.

    Quote Originally Posted by BakaOsaka View Post
    Is there a way to test the PSU standalone? This machine is dual floppy so I don't have an MFM drive to hand to act as load.
    No. The 5160's stock PSU requires an adequate load. Maybe the two floppy drives are enough. As an experiment, try both of those.

  4. #4

    Default

    You can also load with an IDE drive or two.
    PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step

  5. #5
    Join Date
    Apr 2010
    Location
    Albany, OR USA
    Posts
    940
    Blog Entries
    1

    Default

    I seem to remember someone using an automotive headlamp for a load on the 12v.

  6. #6
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,645

    Default

    Your post #2 has appeared.

    Quote Originally Posted by BakaOsaka View Post
    So I've tried connecting an MFM drive that I took out of a Compaq Deskpro to the PSU in isolation and it still itsn't working - I'm assuming the PSU has issues.
    It is easy to fall for the trap of inadequately loading the PSU. Different makes and models have different requirements. It is easy to think something like, "This big MFM hard drive draws a lot of power at start-up; that will do as a load.", but it turns out that the drive draws most of its power from the +12V line and not much from the +5V line, and the particular model of PSU requires the adequate loading on its +5V line.

    Quote Originally Posted by BakaOsaka View Post
    Does anyone have a list of capacitors required for the stock 130W PSU?
    IBM is known to have used different 'guts' in the PSU's over the years. Therefore, if someone here does have a list of capacitors, it may not match what is in your PSU.

    If the source of the 'sound of small pop with release of magic smoke' was your PSU, resulting in the fan (DC powered) no longer turning, then one of many types of components could have failed (e.g. transistor). And the 'PSU is what failed' hypothesis implies that the motherboard's C56 and C58 (quote: "were clearly blown") must have failed open-circuit earlier, not affecting 5160 operation earlier.

    Maybe do a visual inspection within the PSU, if not done already. To allow time for the main filter capacitors to discharge, wait, say half an hour after disconnection of the PSU from mains AC power.

  7. #7
    Join Date
    May 2020
    Location
    United Kingdom
    Posts
    17

    Default

    I've just tried connecting the two floppy drives to the PSU with no luck - The PSU is as lifeless as ever, no fan spin or any activity.
    I'll disassemble the PSU and do an inspection once I get the required tools. In the mean time, is it advisable to use a modern ATX PSU with an ATX to AT power adapter to test the motherboard in isolation? I seem to remember that modern PSUs don't provide a -5v rail, however for testing the motherboard alone I assume this won't be an issue?

  8. #8
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,645

    Default

    Quote Originally Posted by BakaOsaka View Post
    In the mean time, is it advisable to use a modern ATX PSU with an ATX to AT power adapter to test the motherboard in isolation? I seem to remember that modern PSUs don't provide a -5v rail, however for testing the motherboard alone I assume this won't be an issue?
    No issue, because none of the components on the IBM 5160's motherboard use -5V (the -5V from the PSU simply being routed to the expansion connectors).

    Same situation for +12V and -12V.

  9. #9

    Default

    It does sound as though there may be a failed component in your supply. Repairing these is not without it hazards.

    A while back I wrote a detailed article on the IBM 5155 computer supply, similar power rating to yours. It may well be worth a read of this article to acquaint yourself with the operations of these sorts of power supplies:

    http://worldphaco.com/uploads/The_IB...WER_SUPPLY.pdf

    As noted it is important to load the +5v rail with a dummy load, or the initial turn on transient at power up will get detected and disable the supply. These supplies have fairly elaborate over-voltage protection and over-current detection too.

  10. #10
    Join Date
    May 2020
    Location
    United Kingdom
    Posts
    17

    Default

    Quote Originally Posted by Hugo Holden View Post
    A while back I wrote a detailed article on the IBM 5155 computer supply, similar power rating to yours. It may well be worth a read of this article to acquaint yourself with the operations of these sorts of power supplies:
    Thanks for the useful info - I'll provide updates once I've been able to disassemble the PSU.

    I've powered up the system board with an ATX to AT converter. The board is in isolation, with only the PSU and speaker connected.
    I have the SW1 switches set as the following:

    1: On
    2: Off
    3: On
    4: On
    5: Off
    6: Off
    7: On
    8: On

    Connecting power to the board via P8 and P9 gives me no response - The speaker crackles slightly at power-up and then provides no more feedback.
    I've tried replacing the RAM chips in Bank 0 with those in Bank 1, however I still get no response. I've also tried reseating the two ICs at U18 and U19 (11/08/82 BIOS), as well as the 8088 at U3. The two BIOS chips did have slight corrosion on the pins, however I cleaned and reseated the contacts. I've ordered some RAM chips, although I'm not sure this is the issue.

    I tested the voltages according to this page, and I got the following:

    P9
    P6: +4.74v
    P5: +4.74v
    P4: +4.74v
    P3: 0.00v

    P8
    P4: -11.58v
    P3: +13.70v
    P2: +4.45v
    P1: +4.45v

    These all look fine to me - Is there anything else I may have missed in the interim? Is there anything that I can do in the meantime whilst waiting for the new RAM chips to arrive?
    I suppose it is possible that the BIOS chips are still defective. I assume this could cause these symptoms?

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •