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IBM 5155 (Portable Personal Computer)

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    IBM 5155 (Portable Personal Computer)

    Hi Everybody!

    After long absence and after having repaired a 5160 with your help I came one week ago to an 5155 along (100$) that has some flaws that I was hoping to fix again with some good advices from you...

    The machine is configured with 256kb RAM, one original 5 1/4 floppy and one hard drive. MS-DOS 5 is the installed OS.

    The symptoms:
    - The units powers on and posts successfully up to 256kb
    - The error code 601 pops up together with the message "Press <F1> to resume"
    - After pressing F1 the PC boots perfectly from the hard drive and prompts readily with "C:"
    - Going to A: calls the message "fail, abort or retry".
    - Going to B: calls the message "insert a disk..." and after inserting a formatted floppy disk it calls again the message "fail, abort or retry"
    - The led in the floppy at any moment lights on and any kind of movement or motor spin is heard in the drive.


    What would be now the reasonable steps to follow to narrow the search of the root cause? I will obey and report back!

    Many thanks to all!

    Kind regards from Liechtenstein.


    "Fail, abort, retry" could be an issue of a dirty drive heads. Run a cleaning diskette through the drive.

    Remember, wherever you go, there you are.


      If your 5155 has the original QumeTrak floppy drive, then your problem is likeky "gummed up" or "sticky" head carriage rails. On the QumeTrak drive, you should be able to easily slide the head carriage back and forth all the way with no "Sticky" spots (with the power off of coarse). If you find the movement is not smooth and easy all the way along the travel of the carriage, the you are best to remove the drive from the machine and carefully clean the rails with alcohol swabs, while moving the carriage to access different parts of the rails. Once you get the carriage moving freely, you should lube the rails with a small amount of silicon lubricant. Don't spray it on. Use a Q-tip or some thing small to apply it sparingly. Don't force the carriage to move if it doesn't move easily, especially if it is not a Qume. Some drives carriages don't move easily and you will knockn the alignment out if you force it. Hope you get it working. Let us know.

      I see Dos Lives On posted while I was writing mine. The head cleaning disk is a good idea also, but it won't fix sticky rails if that's your problem. By the way. I've seen sticky carriage rails on every 5155 that I've worked on.


        The 5155 uses the same floppy drives as the PCjr. Back in the 80's it used to be a weekly ritual
        opening my PCjr and rubbing some silicone on those drive rails !


          Originally posted by mikey99 View Post
          The 5155 uses the same floppy drives as the PCjr. Back in the 80's it used to be a weekly ritual
          opening my PCjr and rubbing some silicone on those drive rails !
          Yep, The Jr was even worse. Due to lack of cooling, everything in the unit got hot and the little fan behind the drive didn't do enough to cool it, so the lube on the rails dried out and got sticky. In fact, one of the drives in my 5155 came out of a Jr, and it has some brown toasty marks on the board from the heat that it suffered in the Jr.


            There has to be something else wrong with that Jr ...

            The fan in the Jr is *directly* behind the floppy drive. And the power supply is split - most of it is outside of the machine, and what is inside of the machine is only 33 or 45 watts depending on the version of the power card. Nothing operating properly should get hot enough to leave "brown toasty marks" on the circuit board.

            (Maybe it was residue from being in a smoker's home?)


              You are probably right Mike. I had just assumed that the drive had been operating in a hot environment when I saw the discolored board and excessively sticky carriage. When I received the drive it was still in the plastic mount with the fan on it but I couldn't verify if the fan had been plugged in. Maybe the guy had his ash tray right next to that poor PCjr and that's why it never had a chance to grow up. Smoking stunt's your growth ya know. Oh well. I suppose I should quit rambling and let this thread go back to it's intended purpose of getting Chris_in_Japan's 5155 healthy.


                Hi guys - thanks for the advices.

                I need other candidate root causes to check to!

                This is what I did so far:

                - I verified the "P10" power supply connector that comes to the floppy drive. I read the 5V and 12V against the chassis. This is OK, isn't?
                - I verified the rails as per ibmapc advice. The head moves easily back and forth. I have to add here that the whole unit looks very clean. Not dust, no overheating signs at least at the first glance.
                - I visually checked the heads. They look clean. I did not undertake any action to clean it in any way (without having a cleaner floppy I wouldn't know how to do it).
                - Removed the belt to check the friction torque of both motor and floppy pulley (I mean here the "big" pulley that holds the disk and that is marked with 50 & 60 Hz white/black pattern (I guess to measure speed with stroboscopic light?). This last one doesn't turn without the belt in a "very smooth" way, I mean with constant friction torque - some torque peaks are perceptible by the hand however feels more as a magnetic field affecting on the pulley than a damaged bearing. I was willing to anyway disassemble this to inspect and eventually lubricate the bearing but no chance: the bearing is well hidden between the pulley and the aluminum floppy chassis and the shaft is pressed fit to the pulley...

                Above all these mechanical things above, it puzzles me that the floppy is really "dead". No light no "try" to spin - nothing. Inmediate "601" after post and then absolutely nothing. Booting without the belt and a disk in the floppy won't fire the motor of the drive neither...

                The controller operates at least the hard drive since after the "F1 to resume", the PC goes and boots from the HD... Certainly I guess this does not means a non-faulty Xebec controller but before chasing a replacement "just in case" I was willing to narrow potential root causes.

                Need to say: I am just an amateur - I have any kind of replacement parts with me that I can exchange to search the faulty component.

                Dip switch is set correctly (I guess): ON-ON for the last two switches = 1 floppy drive.

                So guys, anxious to hear some new lines to investigate! Many thanks again to all!


                  Check to see if the data cable is "correctly" attached. Since it's the only floppy, it should be attached to the last connector, after the twist. (be careful here. The ribbon cable in the 5155 is usually folded over so the connector that looks like it's at the end is not at the end of the cable.) Also check the drive select jumper right next to the data cable connecter on the floppy drive circuit board. It should be set for "DS1". Beyond that, I think you have either a dead Floppy Drive or Controller. You could also check the data cable for open conductors with both a visual check and a continuity check with an ohm meter.

                  from your original post I was not aware that the drive was not responding at all. No light or sound or movement. Otherwise I would not have suggested the "Sticky rails" problem. with sticky rails you usually get some buzzing noises as well as the light coming on before the 601 error. If you get no movement or light from the drive then your problem is electrical,not necessarily mechanical in nature.
                  Last edited by ibmapc; April 15, 2013, 10:16 PM.


                    You have a 5160 as well.
                    Both the 5155 and 5160 were supplied from the factory with the same floppy controller card - the one pictured [here].
                    If your 5155 and 5160 have that same card, have you tried the card from your 5160 in the 5155 ?

                    Have you tried the 360K drive from your 5160 in the 5155?