Here is a good way to power the old 41 when recharging batteries.
I used 2x mini usb sockets, side by side. They just fit into the recharging socket on the side of the 41. The left one is setup for 5v power from the PC and attaches via 2 wires down the 2 holes onto the keyboards power pads just below.
Currently the right plug is unwired, but I thought to get a 41CL upgrade and maybe use it as the upload/download plug, instead of the awkward port plug those guys at Systemyde have.