Caps Lock, Num Lock, Scroll Lock all permanently on, keyboard not responsive

[E3E]

Can anyone help me with this? I took apart my NTC (Nan Tan) 6151 keyboard to try and see if I could add some diodes to the PCB to try and eliminate some ghosting/add NKRO.

I had it open in a key testing program, and was checking the positioning and effect of diodes when all of a sudden, the keyboard became unresponsive and all the indicator lights remained locked on. I'm using the keyboard through a DIN > DIN to PS/2 > PS/2 to USB adapter.

I've tried it on another PC, I've rebooted this one, and I have also plugged in another PS/2 keyboard to the adapter, and everything points to something wrong with the keyboard. The other PS/2 keyboard is fine. The NTC 6151 does not respond on any computer.

I'm fearing I somehow bricked this board. I really liked it too, but I originally bought it to salvage the blue alps it has for an Infinity build. I grew fond of it though and did not want to salvage it anymore. Instead, I wanted to modify it, but it looks like I screwed it up in the process. There has to be a solution here. Did the controller get bricked, could it be a PCB component that I ruined?

Any help would be much appreciated. There was a thead a while back where someone with a Noppoo Choc Mini faced the same issue but there was no solution and the thread just went cold.

I guess if all turns out sour, I could harvest the switches like I first intended. :/

[chyros]

I had something just like this once or twice while I was testing for faulty connections and accidentally connected two wrong pins but it went away every time after I rebooted it. I've also had a faulty Focus (typical) that never did anything but this; in retrospect I suspect that might've been a capacitor. So if something DID fry I'm guessing it'd be a capacitor.

[E3E]

Thanks for chiming in, Chyros.

I just switched out an electrolytic capacitor, but it seems like that didn't do anything. There was only one of those on the board, while the rest were ceramic. I hear that it's very uncommon for ceramic caps to go bad, and for ALL of them to have died just seems really unlikely.

Not sure what it could be! I'm using a DIN to PS/2 to USB daisy chain in order to hook the board up to my computer. No PS/2 port here. I do have a much older computer that has PS/2 though, but it isn't set up.

Could something have locked the keyboard in its current state? Could it have something to do with the adapter?

EDIT: It seems like it has to do with the controller--it gets REALLY hot when I connect the keyboard. Changing out the capacitor didn't help, and the ceramic caps didn't seem to have any issues. The board still turned on when I removed two of them (locked/stuck indicator lights), whereas if the electrolytic cap was removed, the board wouldn't power up at all.

So I'm guessing it's a controller issue? I'm wondering if it might fix itself if I plug it into a PS/2 port. Is this thing bricked? I don't think flashing this is an option. That's way beyond me.

[Findecanor]

Maybe you shorted something before ...

Anyway, if the controller blocks ghost keys then you can't just add diodes and get N-key rollover. The controller needs to be changed to one that does not block key combinations that it thinks could be ghost keys.

[E3E]

Maybe you shorted something before ...

Anyway, if the controller blocks ghost keys then you can't just add diodes and get N-key rollover. The controller needs to be changed to one that does not block key combinations that it thinks could be ghost keys.

The keyboard is from the late 80s, it does not block keys (and consequentially, can have ghosted keys depending on key combos). This is why I considered it. I have no idea what I shorted, but the problem seems to be related to the controller most likely, as I've changed out all the caps to no avail. All I was doing was testing the keys, pressing them and mechanically holding a diode to the switch contacts and column in the matrix to test. It seems strange that I could've screwed something so bad by just doing that. I'm not sure if the PS/2 to USB adapter is to blame, but that seems unlikely too. I can't test it on a native PS/2 input, but my other PS/2 keyboard works fine using the adapter, so...