This Novag Constellation was bound for the dustbin. It squealed continously and flashed all of its LEDs. Nothing I did changed that.

Since I had started collecting chess computers the design of this type of Novag had intrigued me. A Chinese Puzzle of a chess computer with no obvious way of opening it. Undoing the screws at the back gets you nowhere.

The answer is to use controlled force on one of the side panels. These are held on by shallow plastic 'lugs' that sit in grooves and they have to be eased out of the grooves, with no easy way of prising them out. Watch out for plastic shrapnel.

Once a side panel is off, the front shiny metal strip slides off and the other side panel is easy to dislodge. Of course the screws also have to be removed.

To separate the two halves of the case you have to detach the four push-on ribbon cables around the edge of the PCB.

With the back off of the Conny this is the sight that greets you. I could not see anything wrong with mine. So disappointed I put it back together again for one last futile attempt to get it going, then into the dustbin.

Surprise, surprise it worked perfectly !!

All I can think of is that one of the ribbon cables had become dislodged or corroded and that taking it off its connector and replacing it again had done the trick.

If I had known about it at the time a squirt of contact spray on each of the cables would have been a good idea too.
 

and here is the Conny back working again.