I have an iMac need to reset pram. The keyboard is a Dell usb. sense my apple wireless quite working. how can I reset the pram because I am getting a message says (USB Accessories Disabled unplug the accessory using too much power to re-enable USB devices) This message makes no sense Because I can still use USB ports key board & Mouse. This message started after I updated to High Sierra 10.13.2
iMac, macOS High Sierra (10.13.1), Sierra 10.13.1
How to reset NVRAM on your Mac - Apple Support if you cannot figure out the Dell keyboard then you may need to replace the Apple keyboard. Are you positive the original Apple keyboard has died? They are normally pretty hardy unless a user abuses it by spilling liquid on it or something similar.
It sounds like maybe the Dell keyboard has an internal fault or bad cord. If your original Apple keyboard it not working or un-paired, then try another Generic USB or Apple keyboard as rkaufmann87 suggest's.
FWIW I use $20 Logitech MK120 Keyboard/Mouse Combo's with all of my Mac's and have no problem invoking any of the Apple Startup Commands. https://www.logitech.com/en-us/product/desktop-mk120
reset pram
