41CL locked up

[Monte Dalrymple]

(05-15-2016 07:44 PM)JurgenRo Wrote:  My 41-CL (V4 board) does not switch on with the On-button. By chance I figured that the only way to switch on (and switch off) the unit is with the Backspace button! But it merely comes up with a Display containing only @ signs. Absolutely no response to keystrokes.

I tried to get a Memory Lost condition by removing batteries (left them out for about 12 hours), short-cutting the battery poles and also with the reset keystroke combination (Backspace - On). But nothing helped. Also, the machine does not switch off automatically after some time of inactivity.

Would appreciate any ideas to get it back to life ...

Odds are that there is a poor connection somewhere - either between the CL board and the calculator main board (most likely) or between the battery and the calculator main board. So these are the first things to check. The @ symbols in the display mean that the DATA line is not making it to the display driver from the CL board.

The other possibility is that the display driver is in a state where it doesn't sync with the CL board. Both have power-on-reset functions, but the one in the display driver seems to get "confused" sometimes. You might try taking the batteries out and pressing the ON button. Pressing ON starts the power-up process, but with the batteries out this has the effect of discharging all the capacitors in the power supply, which will eventually clear any retained state information in the display driver.

I once had to let one of my machines sit for a couple of days after taking out the batteries and pressing ON before it would start up again properly. But the CL board worked fine in another calculator body during the waiting time, so there is something in the display driver....