Keyboard port is actually 12V?

[masto]

I noticed the MJP technical manual says there's 9V on pin 3 of the keyboard connector, but I measure 12V there. I'm assuming that it's just a mistake in the document, but on the off chance that my NABU is weird or I'm making an error in measurement, I'm curious whether anyone else has checked this voltage.

[DJ Sures]

In December before I went to my cabin, I was probing the keyboard connector to connect an arduino with a rs422 shield like you had done. And I also noticed 12v - but I didn’t check with load. There’s a massive resistor raised on the pcb from what I recall. I wondered if that’s part of a divider to get 9v, i that case it would need load for a correct measurement.

[masto]

If I load it down with 300mA, it drops to 9v. I'm tempted to measure the current consumption of the keyboard, but at this point I think I'll go back to the actual project that I was in the middle of.

[DJ Sures]

From the heat generated on the keyboard, it might have a similar current draw