Are you sure it's the keyboard connector at fault?

There is often trouble on the area surrounding that port as it's historically where the CMOS battery is... And when it leaks the first symptoms can be keyboard errors.

It could also be that the fuse on the keyboard port has gone (if your board has one - they protect from spikes due to hot plugging).

Finally another possibility is that the keyboard controller chip has died.

CMOS battery seems fine, and the time/date and BIOS settings seem to be properly stored on boot. No visible leaks or damage from previous leaks and the battery is actually pretty far from the plug on this one, so I feel pretty good about discounting that.

Not sure if there's a fuse on this thing. No mention of it in the documentation (frustratingly, it does mention the motherboard is "PS/2 optional", which may have made things easier). Any easy way to tell from the board itself?

The keyboard controller having died is a possibility as well, I suppose, although the fact that I got different results plugging and half-plugging different keyboards at points (i.e. some times I got to make it beep for a keyboard error, sometimes it was just dead) is what suggested to me it may be a physical problem with the connector.

Either way, are you aware of a way to bypass the whole issue with different hardware? This board has a few pins for an add-on PS2 and serial mouse board, which I have, but the keyboard seems to be handled solely through the soldered-in DIN connector, although maybe there's a way to work around that.

I think some boards have a fuse for the keyboard convector. I've a similar problem, where some keyboards worked and others don't, ans sometimes the same keyboard worked a sometimes not. It was the fuse.

Two people pointing at it. I suppose it's worth investigating. Now the question is how to go about finding whether that fuse is there and where.

What's the fix for the fuse problem, in any case? Is that an easily replaceable piece? I'm not a soldering kind of person, so I was trying to avoid replacing the plug, but say what you will about it, you can get five for a dollar each online and it's just five big pins. How hard is it to fix/replace the port fuse?

EDIT: Found this

486 GA-5486AL Motherboard issues.

Which is related. There IS a F1 label near the port, which I guess is the fuse. Seems like it would be just as annoying to replace and probably harder to find, so... yay? Anyway, it doesn't look damaged at first glance. I suppose I could try shorting it with something to see if it behaves differently.

GoleMMan wrote on 2021-05-08, 12:02:

EDIT: Found this

486 GA-5486AL Motherboard issues.

Which is related. There IS a F1 label near the port, which I guess is the fuse. Seems like it would be just as annoying to replace and probably harder to find, so... yay? Anyway, it doesn't look damaged at first glance. I suppose I could try shorting it with something to see if it behaves differently.

you'ld better post a photo, because the only photo in the thread you linked to is a bridge wire, labeled as a fuse. If for some reason you have a problem with that wire it most certainly will be a bad solder joint and not so much the wire.

That thread is just somebody who had a similar problem and replaced the fuse with a wire. My board still has the fuse in it. I haven't been able to check if the fuse is intact or not yet, but as soon as I get my hands on a multimeter or have some time to bypass the fuse I'll report back.

You cant test it with a tester or simply jumper it with a wire to test, that's what I did. But there's some risk that jumpering the fuse will blow something.

Yeah, but I will have the right gear soon and, believe it or not I don't actually have a proper wire handy. I was surprised to find out, too 😀

If the fuse will actually be the problem, you don't necessarily need to replace it with one that looks the same, i think that modern resettable 500 miliamp PTC fuse would be fine. Certainly better than a wire (a wire can work, but can damage something - better remove it quickly if something starts to heat up during test 😜)

Thanks, I'll keep that in mind. That definitely sounds easier to jam into the exposed wires of the old fuse than it'd be to desolder the five pins of the connector from the motherboard's PCB and solder in a new one.

From what I hear around it's either the fuse or the connector itself has deteriorated and won't make a contact. Once I have the right materials accessible it should be pretty straightforward to diagnose which is the problem.

So I managed to slap a multimeter on it and... yep, you guys were right. The fuse is blown. I'll look to having it replaced, or at least bypassed.

Thanks for the help in diagnosing this.