Hi... the setup I'm having trouble with is super basic. Alesis VI49 controller keyboard MIDI out connected to Motif-Rack MIDI in. The controller gets power from a 9V AC adapter, there is NO computer/USB involved. Motif-Rack is set to receive on MIDI channel 1 and the controller is sending on channel 1. The controller is also set to send MIDI via USB and DIN.

Without a computer you will need to connect to the Motif-Rack via a standard 5-pin MIDI connection. MIDI OUT of the keyboard controller to MIDI IN on the Motif- Rack.

In order for the Motif-Rack to work via USB, you would need a computer and the Yamaha USB-MIDI Driver for your Computer Type.
You cannot just connect a controller directly to the Motif-Rack with a USB cable.

So MIDI I/O should be MIDI.

Could it be possible that the 9V power adapter on the controller could cause an unreliable signal if it is sending 400 ma instead of 500?

That is a question for Alesis.

In general: Amps and milliamperes are a measurement of the current *drawn* by a device (not sent). A device will not draw more current than it needs. Problems arise when it needs more current than it is being supplied... that’s when overheating, catastrophic failure, and even fires can occur. So make sure you supply your alesis device the recommended power it requires. Don’t mess around with electricity. Just because the lights are on does not mean it’s happy... and working properly.

Getting the Voltage right is easy... what folks overlook at their own peril is the Amp requirement. Current is amperes and represents the flow of the electrons. It’s never the Voltage that kills you, it’s the Amps...
You can standup in a foot of water, no matter how big the body of water, but start moving that water your ability to standup starts to quickly diminish. It’s the current that will knock you down. Overlook this bit of science at your own risk!