Sounds like my HMC's. They are originals and will not work on Power 7
Here's a link to start with.
Although normally they tell you, on a new system install, to not even
think about plugging in the Power x box until you have the HMC wired up
and connected. Gotta be a different story for those who are changing
Expand Systems Hardware information, Power Systems information, Power 6
information, your system type (for example, 8203-E4A), Working with
consoles, terminals, and interfaces.
Perform all the necessary tasks in "Installing and Configuring the
Hardware Management Console.
See also, Managing IBM i consoles, Changing consoles...