keenmaster486 wrote:

I can't find a schematic for this thing anywhere on the internet. Does anyone have any ideas as to what kind of switch that is and how it should be soldered in?

Look at the physical construction of the switch in the first image. The outer two solder pads are mainly mechanical support for the switch, they're connected directly to the switch's outer casing.

This leaves the middle three solder pads. The centre pin is be common, and will be linked to one side for AT mode, and the other for XT.

Your keyboard will need a Single Pole Double Throw (SPDT) switch connected to the middle three solder points, and you'll also need to break that little connection just below where the switch connects.

By golly, I think you're right... and on closer inspection (high res photo here), I think you're also right about breaking that solder bridge.

Thanks a lot, sir! I'll be soldering that in pronto, and we'll see if it works!

Are you 100% sure that everything else is the same on the other side of the PCB?

Well, I'm 95% sure, which is good enough for me 🤣
There's actually no way to tell at this point, since there's no corresponding picture on that website that I can use to compare. I'll probably just solder the switch on and see if it works.

Also by the looks of it, a single pole single throw switch would suffice, as the other pole is not connected anywhere. So it may be enough to just either short the two pins or let them be disconnected.

Say, you may be right there... I'll try removing that solder bridge first and see if that makes it work.

The most I can do right now is confirm that it's not in AT mode, since I don't have a monitor for my XT board yet (fingers crossed, it'll be here Tuesday!)

keenmaster486 wrote:

Hi everyone,

I got this model keyboard a few days ago, because it appeared to have a switch for XT/AT operation on it. But on closer inspection, the switch is missing!

By the looks of the photos, I would say that this particular model was not manufactured for switchable AT/XT operation. I would also assume that it is also missing other important components in order to work in AT or XT mode.

The model number on the PCB says KB-6251EA, which matches the link I posted. Mine is marked version 6.0, though, as opposed to version 5.0 on that webpage.

But the case on my keyboard has a clearly marked slot for an "8088/80286" switch. I'm inclined to hope that it was a manufacturing error, and the switch was omitted.

I severed that solder bridge with a knife, and it still works as an AT keyboard (plugged into my laptop with an AT/PS2 adapter).

Brickpad wrote:

keenmaster486 wrote:

Hi everyone,

I got this model keyboard a few days ago, because it appeared to have a switch for XT/AT operation on it. But on closer inspection, the switch is missing!

By the looks of the photos, I would say that this particular model was not manufactured for switchable AT/XT operation. I would also assume that it is also missing other important components in order to work in AT or XT mode.

Without seeing the whole PCB, I'd say the trace just goes to a pin on the keyboard's controller chip.

And by the sounds of things, that's the case.