External keyboard & Mac Powerbook G4

I want to start my old Mac Powerbook G4 in Target Mode a FW to FW connection in order to salvage data on my hard drive.

Because the original keyboard does not work (the ribbon has been severed due to repeated removals), I've tried using an external keyboard connected to the USB port. However, the good Mac does not "see" the bad Mac after I hold down the "T" key during boot.

Wondering if the start-up process does not "see" the USB-connected keyboard in time to permit the Target Mode command to take affect?

Or is there another issue?

Thanks in advance