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BOTH my IBM 5155s aren't working!

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    BOTH my IBM 5155s aren't working!

    I own two IBM 5155 portables, that I used to use back in the early 1990s to program multi image slideshows, with the help of an 8-bit card that interfaced with the slide dissolve modules. One of these worked fine three years ago, the other was last tested a bit further back. Anyway, today I take them out, flip the switch, and - nothing! Both of them are pretending to be doorstops. No bad sounds, no smoke, nothing. I opened one up and found the boards to all be just a bit loose (where did all the hold-down bolts go, anyway?) so I reset them and tried again. Again, nothing.

    Can someone suggest a course of action to test these machines further? I actually still want to use them!


    Here they are in happier times (2003)

    It sounds like the power supply isn't coming on. This could be due to a short somewhere on either the +5 -12 or +12 V lines.
    Tantalum capacitors are notorious for shorting internally and one shorted on the MB or a card can prevent the power supply
    from coming on.

    It's usually a process of elimination, removing cards/drives/MB etc until the supply will come on and then determining whats faulty.
    I would try removing all cards and see if the supply comes on, I think it does have a fan in the rear, see if the fan is spinning.
    If you have a voltmeter check the voltages on one of the power connectors that attaches to the floppy drive. One should have
    +5 V (red) and the other +12 V (usually yellow).

    EDIT: There is good troubleshooting info on modem7's site...check this url for some common problems......

    Also more general info here under IBM 5155 :
    Last edited by mikey99; January 29, 2015, 07:38 PM.


      Welcome to these forums Steve.

      There is a lot of IBM 5155 information at

      There is a thorough diagnostic procedure at [here]. If you have a shorted tantalum capacitor, it will lead you to it.

      But perhaps before you start that, have a good visual inspection, if you have not already. In particular, look at the tantalum capacitors because there may be a visual indication of failure. What you are looking for is shown in the photos at the top of [here]. But as people will tell you, often there is no visible indication of failure. That is where the above diagnostic procedure helps.


        OK thanks for the direction. I pulled all six cards, and examined them and as much as I could see of the MB. All the bits on all the cards look clean and intact. I tried turning on the PC with all the cards out; I figured it would go through the ram-check at least if it could. I got nothing. I will figure the logistics of testing the MB (as described on that minuszerodegrees page) as it sits in the PC tomorrow!
        Last edited by SMichelsen; January 30, 2015, 09:03 PM.


          Welcome to the forums! Let us know how the testing goes. It'll be easy with a voltmeter to check your power supplies too. Definitely check your power supply area first. I don't recall if there are any fuses in the back that could impact things or if they have the 120/240 switch on the power supply. Those are also two easy fixes. If the system did power on you'd see the floppies check themselves I think so it shouldn't just be the brightness/contrast knobs being all the way low
          Looking to acquire: IBM 5100, Altair 8800


            OK, after a month of not getting a chance to even touch my "problematic" 5155s, I am back at looking at them. To be clear about the problem, here is a very short video that shows what happens when I turn it on... I get nothing more than a 2nd click from the power supply. Please listen here...

            My question now is, is the procedure described at
            still the most appropriate place to start? Thanks!


              Originally posted by SMichelsen View Post
              My question now is, is the procedure described at
              still the most appropriate place to start?
              Yes it is.


                Originally posted by SMichelsen View Post
                I own two IBM 5155 portables, that I used to use back in the early 1990s to program multi image slideshows, with the help of an 8-bit card that interfaced with the slide dissolve modules.

                What is the 8-bit controller card you are using? An AVL Genesis or something else?



                  Originally posted by nc_mike View Post
                  What is the 8-bit controller card you are using? An AVL Genesis or something else?

                  Yes that's it. I am an ex-multi-image guy...


                    Originally posted by SMichelsen View Post
                    Yes that's it. I am an ex-multi-image guy...
                    Me too, from way back using an AVL Eagle and ProCal back in the early 80's doing 24 projector corporate shows. Not many of us around that still know that world If you EVER want to part with one of the boards let me know!! I'd love to get my hands on some working gear and dabble in it again



                      Originally posted by SMichelsen View Post
                      ... I tried turning on the PC with all the cards out; I figured it would go through the ram-check at least if it could. I got nothing...
                      When you say "all the cards out" does that include the CGA card? I've seen a few cga cards with shorted caps on the +12v that would prevent the power supply from coming on. Also, be aware that the 5155 power supply will not come on with insufficient load as well. So, if you try to test with the power supply leads disconnected from the MB, It will not come on then either. If you did try it with all the cards out and the floppy power connectors disconnected and still no go, then you might try removing the ram chips. I believe a bad ram chip also can prevent power up.

                      By the way, where are you located. I have two working 5155s and would be happy to help with yours if you are near me. I'm near Albany, Or.