41CX fast timeout


I recently got a 41CX that, as far as I can tell, operates flawlessly. The only issue is that the timeout for the display is ~10 seconds, not 10 minutes like my other 41's. You can turn it right back on with the ON key, but if you were entering ALPHA characters you have to start over if you delay at all. Very annoying...

Anyone seen this before?


Did you perform a memory reset (Memory Lost) ?



Yup. Tried the ON with the Arrow key. Also left batteries out for a few days with foil on the calc batt terminals to try to drain any residual memory.
And, as a second note, the timer functions are accurate. I set the clock and only lost a few seconds over a few days before using CORRECT. But the display still time's out after ~10 seconds.


Not easy to fix, guess you are going to have to assign ON to a key and eat batteries and always remember to turn it off.


May also be a hardware defect.

If it's _not_ a halfnut CX, you could test the unit with another CPU board,

to see if the problem comes from the CPU board, the display chip,

or maybe even the connection strips...

The test unit doesn't necessarily have to be a CX. A C or CV pcb will also work.

I had some units with similar symptoms, where the problem were either the zebra stripes and/or the battery contact block.

One unit also had a 'cold' solder pin between the display pcb and the keyboard backplane.

In any case, if ou decide to open your CX, do it very carefully to not crack the screw posts,

and always make sure beeing grounded to avoid ESD.




I have contemplated both assigning the ON finction and taking the thing apart (I've taken a few others apart before) but figured I'd troll the wealth of knowledge here before taking more drastic measures.

Thanks for the responses!



It was indeed a cold solder joint between the keyboard and LCD display. A little touch-up work and presto! Actually, all the connections at the LCD were a bit flaky. Just using the tip of an Exacto blade to test for movement broke away a few of the joints.

Thanks again for the suggestions! It got me where I needed to be to dis-assemble this one and actually fix it!


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