Fullnut 41CX problems



I am trying to repair a Fullnut 41CX for Peter. Apparently, it had contact problems, but Peter said the batteries went hot after switching it on. This 41CX has a logic board similar to the 41Cs, and when I opend the Calculator, this logic board was out of its usual position. This may explain why the Batteries went hot, as it may have sorted some connections.

After cleaning the contacts and fixing the logic board in its normal position, I switched the calc on, but the display just showed "@@@@@@@@@@@@", and the beeper hummed.

I traced some signals with an oscilloscope, an found that the DATA,phi1 and phi2-signals were present though with an amplitude of about 1.7 V. The signals on pin 12 (LCD) was pure noise, so were Pins 6,7 and 8 (LCDC1,LCDC2,LCDC3). Pin 2 (ISA) showed some signals, but also carried a lot of noise.

Did anyone have similar problems or does someone know a cause/solution?

Thank you! Klaus

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