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486 motherboard keyboard interface error

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    486 motherboard keyboard interface error

    Hi guys,
    I had a battery leak on my 486 motherboard and I'm getting a keyboard interface error. I've cleaned it all off and it visually looks fine now. Could it be a damaged resistor? The one near the connecter (F1) has a little black mark. Could it be damaged? Is there a way to know what components are controlling the keyboard interface in order to troubleshoot them? 486 motherboards are really stupidly priced these days and I really want to fix this if I can. See photo. The F1 resistor is what I'm talking about.

    My board is a BIOSTAR 1433 50UIV

    IMG_2738 2.jpg
    Not all those who wander are lost. - J. R. R. Tolkien

    F1 doesn't appear to be a resistor. Given it's "F" designation, likely a fuse. It should read zero (or very low) resistance with a meter. The traces in your photo look to be very suspect, as well.


      Yeah, you are going to have to track down and perform trace repair, or at least jumper over the bad tracks. Corrosion has damaged it.


        F1 is most likely a fuse for the keyboard. Check it for continuity, if it is not continuous, then bridge it from one side to the other temporarily and see if that fixes the issue. If it does, then source a replacement fuse.

        If F1 is continuous and/or bridging it does not make the keyboard work, then it would be something else and I would check the traces in that area.

        IBM 5160 - 360k, 1.44Mb Floppies, NEC V20, 8087-3, 45MB MFM Hard Drive, Vega 7 Graphics, IBM 5154 Monitor running MS-DOS 5.00
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          ok thanks for the replies. I'll check the "fuse" first. Are the track responsible for the keyboard interface? Or does everything pass tough there?
          Not all those who wander are lost. - J. R. R. Tolkien


            With just your photo it's impossible to tell. You'll likely need to trace that down yourself (and you may need a schematic to verify the trace runs).


              The real problem with traces is not so much the visible ones on the surfaces of the board but those on the inner layers. You can repair those that are on the surface but not so much those on the inner layers.
              PM me if you're looking for 3" or 5" floppy disks. EMail For everything else, Take Another Step


                Originally posted by robbo007 View Post
                ...I had a battery leak on my 486 motherboard ...

                I'm very concerned about that battery on that board. Looks like you replaced a NiCad rechargeable Battery with with a TL-5151 Non-Rechargeable; 1/2 AA; Lithium; 3.6 VDC. See the label that states "RISK OF FIRE OR EXPLOSION, DO NOT RECHARGE". You're asking for trouble if your board tries to charge that battery! You need a diode in there. Or, better yet, cut that thing off and connect an external battery pack to avoid damage from another leaking battery.

                Last edited by ibmapc; July 10, 2019, 08:16 PM.


                  Alternatively, if you're handy, you can just disable the charging circuit.

                  The engineering manager I worked with back in the 70s was quite firm: "Batteries don't belong on a PCB" and resisted any suggestions in that direction. Of course, this was before the potted-in-resin Dallas chips. In general, I've got to grudgingly admit that he was, by and large, right.
                  Reach me: vcfblackhole _at_ protonmail dot com.