Quote Originally Posted by SomeGuy View Post
It sounds like the IC chips on the keyboard could be damaged.

When it is apart, it should not think a key is pressed, and the photo of it doesn't really look too bad. A problem on the motherboard could, I think, also cause that issue. Given the other errors, there could be damage to the motherboard.

I kind of doubt it would even be a single keypad, but rather a damaged IC always reporting back the same key.

And you probably already figured out, with capacitive keyboards the disk on the form pad should not be conductive, it acts as a varying capacitor, so there should never be continuity between the metal pads.

If it were me, I would want to at least narrow things down a tad more just to make sure there is nothing wrong on the motherboard. I have not tried it myself, but someone previously posted that they were able to wire in a generic XT compatible keyboard. They reported that it does use the standard IBM PC/XT keyboard protocol (not AT), but the main difference was 1: the presence of an extra reset wire that is not used by other keyboards, and does not need to be wired in. And 2: The Compaq proves a different voltage (12v instead of 5v if i recall correctly) so you would need to covert voltage or use a different power source, otherwise things could go boom boom.

Just a thought.
Using the following links I managed to wire up a standard (Zenith) XT keyboard I had:
* http://www.vcfed.org/forum/showthrea...roded-keyboard
* http://www.instructables.com/id/7805...Easy-Tutorial/
* https://allpinouts.org/pinouts/conne...oard-xt-5-pin/

As noted in the vcfed forum link, I do still get a 301 error however the keyboard does work as expected.

So, Compaq Plus with newly attached XT keyboard works. Can anyone suggest how I could narrow down why the original keyboard produces a "52 301" when its just the keyboard circuit board attached?