So you powered up your EDC 501J and you are getting strange readings on the
rear banana jacks?

It turns out you need to install some jumper links into the amphenol
connector in order to make the banana jacks functional.  This is because
the amphenol connector serves as a remote 4-wire sense / force pinout.

See https://www.eevblog.com/forum/testgear/edc-501j/msg642484/#msg642484