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Thread: Compaq Portable Plus keyboard circuit issue, VDU and floppy card issues

  1. #1
    Join Date
    Jul 2017
    Location
    Norfolk, UK
    Posts
    12

    Default Compaq Portable Plus keyboard circuit issue, VDU and floppy card issues

    I was lucky enough to buy a Compaq Portable Plus reasonably cheaply but it has a few problems and I could really do with some advice! I'm having fun but still very much learning, generally still needing some handholding if anyone can.

    (Please note as a newish member I may not be able to respond without administrator review, there may be a delay in me responding)

    Errors shown:
    301 - Keyboard issue.
    401 - Printer failed.
    501 - Video controller issue.
    601 - Floppy disk issue.

    301 Keyboard
    I have stripped the keyboard back to just the circuit board but unfortunately on boot I still get "52 301" on screen with a continuous stream of beeps. To me that means the computer believes a keyboard key is being held down.

    Without the keyboard I canít get a lot further with diagnostics.

    I believe this is to do with some corrosion on the keyboard circuit board which I wiped away with alcohol. It looks like someone had split something on it.

    Google indicates that "52" is the Zero/Ins key which appears to be the right area for the corrosion (pictured).

    If I detach the keyboard entirely I get "301" error code which seems both about right and to indicate the error is with the keyboard circuit board and not something more involved.

    I understand the basics of how the capacitive keyboard works, having previously repaired the foam in a keytronics keyboard (and now having a stock of OHP sheets, draft excluder and anti static bags). I also have a Multimeter. Unfortunately I have no idea how to use the multimeter to test for the issue and more so I have no idea how I might go about fixing it.

    I have tried to run something between the pads on the board to clear out any corrosion. I also gave the area a bit more of a scrub with alcohol. However, having no clue I'm worried I might make it worse so these actions were a little half-hearted.

    401/501/601 VDU Card and Floppy Controller Card are Zapping Power When Inserted
    Whenever I plug the VDU Card or the Floppy Controller Card in to ISA slots the red light in the centre of the mother/system board briefly illuminates and then goes out. Without them plugged in the red light stays on and the computer attempts some kind of boot.

    It also had a network and ram card fitted, these do not have the same effect, in that the light stays illuminated and it boots.

    I am currently running it with a 16 bit Acumos AVGA1 ISA card, which also works in an 8 bit slot (which is why I hunted one down). With this card it boots with the aforementioned "301" keyboard error code, in addition to floppy and hard drive error codes.

    I've tried unplugging the power from the floppy and hard drives, no change.

    I've tried unplugging the inbuilt monitor from the VDU card, no change.

    I've tried unplugging the floppy drive from the controller, no change.

    I've tried moving the cards around different slots, no change,

    Again, no idea. I have a multimeter but don't know how to use it. To me the above means my VDU and floppy controller are faulty but it occurs to me there might be other possibilities and I might be able to use the multimeter to narrow that down.

    Its not quite the same prioritity as the keyboard, but not having a working floppy controller means my options are still limited when doing further diagnostics.

    Hard Drive
    Given the main selling point of the "plus" model seems to be the hard drive I figured someone might ask about booting off it. Its currently showing a 1701 error. I've no idea if thats the hard drive, controller or something else. I'm not really looking in to it at the moment as compared to the other problems thats less important.
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