Weird HP-71B behavior...

[J-F Garnier]

(08-29-2018 07:44 PM)KF6GPE Wrote:  Joe, I did try shorting the battery contacts at first, did it again this morning, no luck either time. It's unresponsive to on-/.

You should, as Joe suggested, try shorting the two farthest terminals in the card reader slot, not the contacts in the battery slot because there is a diode in the battery supply path.
Be sure to remove the batteries first!

J-F