To control the Maslow I use a wireless keyboard, which is very useful as I can operate the Maslow at close quarters rather than being tethered by a keyboard cable to the control computer. Unfortunately I was using it recently and dropped it on the floor. This has happened beofre but this time when I picked it up and tried to use it, it wasn't working. It looked like the supply wasn't connected any more.
I took the keyboard apart and there was a dodgy looking inductor from the batteries to the PCB. I checkd with a multimeter and it was open circuit. I replaced it with a wire and checked. The keyboard started up and the keys worked, but the trackball didn't work and the low battery LED filckered. So it looks like the inductor is necessary to smooth out the supply voltage or help with transients. I didn't have any inductors, at least 100uH ones.
I chipped the paint off the inductor and found a ferrite core. The problem was the connection to the windings. The core seemed sound so I got some wire (the same wire I used when connecting the eMMC chip to the USB adapter) and rewound the inductor:
This fixed the keyboard, the trackball now works well.