On Thu, 3 Jan 2019, JC wrote:

If you remove the case and look at the top board, near the 8088 processor (40
pin DIP, fairly obvious) there is a plug marked RESET. Move it to the reset
position. That will stop the digital board from running and assuming you have
no serious faults will turn the scope into an analog only scope.

There is a jumper (connects 2 out of 3 pins) with the label RESET near its
rightmost position. It was in this position. I moved it to the leftmost
position and now everything is perfect (for me).

Removing yhe case was difficult but possible after I removed the 2 screws of
the little side panel and the 2 nuts of the IEEE connector.

Thanks to you. :-)
--
Jean-Pierre Coulon