Hopefully you didn't overload the keyboard controller on the motherboard and fry it. I would check the keyboard socket for maybe a bad solder connection and check the traces from the keyboard port to the keyboard controller chip for burnt traces or components.

Ok, I got response from the maker of this adapter: "To protect the motherboard, a logic level converter (the smallest board) is installed on the adapter board."

"Furthermore, each motherboard has a fuse on the +5 volt line, I recommend checking this fuse.
Your motherboard is kept safe by these two safeguards.
Perhaps due to the high consumption of the keyboard, the fuse needs to be replaced."

So hopefully just fuse problem. I haven't spot any visible issues on the motherboard. I don't think it will be a bad solder connection. This week the machine was running daily.

Can you post pictures of the motherboard?
Check on the keyboard V line if it goes to a filter (inductor) and check if it reads 0.06 ohm or higher, if higher it could prevent the correct voltage.
Just a thought.

As Nexxen said, a picture of the motherboard (or the make and model would be helpful). If no keyboard is connected does the motherboard boot but halt with KB error like it should or does it do something else ?

Horun wrote on 2021-06-02, 23:19:

As Nexxen said, a picture of the motherboard (or the make and model would be helpful). If no keyboard is connected does the motherboard boot but halt with KB error like it should or does it do something else ?

Yes, if keyboard not connected, it goes through POST and report KB error.

The board is ASUS 486-PVI-486SP3.

NOthing looks blown.
Could you check C1,2,4,17 and 18 if one has a higher resistance than 0.6?

You probably should take out the motherbaord at some point to check continuity between motherboard and keyb port.

Yes, I was thinking the same. I will check the parts in 10 hours. Thank you for help!

Maybe check if this applies to your motherboard, maybe you can avoid pulling out the mobo.
https://diagramweb.net/img/ps2-keyboard-to-5- … -diagram-12.gif

Nexxen wrote on 2021-06-03, 00:58:

Maybe check if this applies to your motherboard, maybe you can avoid pulling out the mobo.
https://diagramweb.net/img/ps2-keyboard-to-5- … -diagram-12.gif

Funny that it's in Czech language...which is where I am right now. Anyway I have experience with software and Teensy. But this part, I bought on E-Bay. It worked for me with some cheap Genius USB keyboard. And the guy have working video on Youtube plus he is doing PC XT converters like this for a long time. This AT is just something new right now. So based on that, I would trust him, he knows how to connect the pins and shielding. I may raise a question, though.

But I should not connect the Teensy to USB 5V. He clarified it is not needed. Which I did not know and the RGB keyboard won't even run without it. So I guess if there is some voltage from PC DIN (I guess 3.3V). Then there is some logic converter 3.3V to 5V. Then there is Teensy USB with additional 5V power line (probably extra), then there might be some problem like current going in from both sides and it might bring 5V to PC DIN under some special condition (like USB device, in this case the keyboard, gets disconnected). Maybe something like reverse polarity and it might blow up the fuse or something else on the board.

Check continuity on the 125v rated green fuse at the top left; it protects the keyboard/keyboard from over-voltage and shorts.

I had similar issues on my identical PVI SP3 ("no keyboard detected", "keyboard failure" - a quick flash of lights on the Kb itself, and then nothing) and it turned out the fuse had blown.

megatron-uk wrote on 2021-06-03, 07:18:

Check continuity on the 125v rated green fuse at the top left; it protects the keyboard/keyboard from over-voltage and shorts.

I had similar issues on my identical PVI SP3 ("no keyboard detected", "keyboard failure" - a quick flash of lights on the Kb itself, and then nothing) and it turned out the fuse had blown.

Okay, my keyboard does not even light up. I will need to measure it today.

Keyboard error and faulty fuse:

Removal and replacement of the fuse:

megatron-uk wrote on 2021-06-03, 09:08:

Keyboard error and faulty fuse:

Yes, that might look like it. Either the fuse or Amikey controller. But how to measure anything on the fuse? Fuse is only for current, you cannot measure any voltage or resistance on fuse, right?

No resistente can be measured and Is 0 . It Is infinite fuse Is broker and Need replace

Yes, just check the continuity of the fuse - put your multimeter into continuity mode and (with the computer off!) put one probe to one side of the fuse and the other probe to the other end. It will vary on your model, but on my (ancient) Fluke 75:

My guess is that there is none, your multimeter will not beep (most models will beep when they show continuity - or at least less than a trivial amount of resistance) or will show open-circuit or similar - ergo it will prove it has blown.

If it doesn't have continuity testing mode, just select resistance and measure it - in that mode it will show infinite resistance if it is blown.

megatron-uk wrote on 2021-06-03, 10:03:

Yes, just check the continuity of the fuse - put your multimeter into continuity mode and (with the computer off!) put one probe […]
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Yes, just check the continuity of the fuse - put your multimeter into continuity mode and (with the computer off!) put one probe to one side of the fuse and the other probe to the other end. It will vary on your model, but on my (ancient) Fluke 75:

IMG20210603110448.jpg

My guess is that there is none, your multimeter will not beep (most models will beep when they show continuity - or at least less than a trivial amount of resistance) or will show open-circuit or similar - ergo it will prove it has blown.

If it doesn't have continuity testing mode, just select resistance and measure it - in that mode it will show infinite resistance if it is blown.

Yeah, I have only this DSO Nano v3. I updated the firmware, so it has some apps to measure voltage and resistance: https://www.seeedstudio.com/DSO-Nano-v3.html ...but normally it is oscilloscope