AFTER SEVERAL YEARS of using my trusty HP Scanjet 4890, I've learned several things about living with USB powered devices. I'm careful of USB hubs because I've been in several situations where my scanner misbehaved because it was connected to an unpowered hub or the hubs power adapter was disconnected. Some powered hubs do not include the power adapter as a standard item--something I've also discovered to my frustration. Some hubs cannot handle more than four full-power USB devices. In my case, I can get data drop-off to a connected USB hard drive and when that happens in the middle of a scanning job, my scanning software often crashes. In most cases, when I suspect an issue with a USB device, I move the unit most important to my work to a USB slot that is directly connected to my computer's USB port. Even that can be problematic because I've discovered the rear ports on some of my older laptops just don't work anymore. All important lessons learned while working with USB devices.
Photo of my HP 4890, working well since 2006.