Help with HP-71B

[Joe Horn]

Some thoughts: After seeing the Memory Lost message, you have to wait a few moments before the keyboard becomes active, so be patient. If you have an HPIL module installed, then you'll have to wait even longer, since it's trying to send the display out the loop. After you see Memory Lost and wait a few seconds, press ON until the message is cleared, then type OFFIO (or DISPLAY IS *) and press Enter. This will stop the IL module from trying to send the display out the loop and speed up keyboard response.

You say you removed all the modules. Does that includes the HPIL module? Does pressing ON after waiting a few seconds STILL does not clear the Memory Lost message?