I added a switch to a velleman pcs500(amazing that they didn't add one but I should have known better) because for some reason it does not automatically turn off when not in use. In any case I'm wondering if there can be any detrimental effect by doing this? There are no inductors on the circuit board so I don't see any issue with kickback. It uses 9VDC and I added the switch between the power jack and the circuit board.
Thanks, Jon