I'm
pretty sure 
that you will get a soft click noise from a solenoid activating when you press the shutter release. I believe you will hear this even if the motor is out as long as you have power. That might help determine whether it is the motor or some other internal bit.
If you want to cobble together a battery adapter for one of the rectangular 9 volt batteries you could probably do that well enough to determine if there is an issue with your power adapter. Having done that, shorting pins 1 and 3 in the charging socket to activate the motor would verify that all was well at the release button.
Worst case, I emailed HB last month and thy said thy still offer service on this model.