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ElectroStatic Discharge: a possible solution for the HP48

Posted by Vieira, Luiz C. (Brazil) on 27 Nov 2002, 7:25 a.m.

Should you experience unexpected behavior in your HP48 and suspect it is related to ESD (ElectroStatic Discharge), there is a keystroke procedure that will allow you to check for it and return the calculator to its normal operation. This keystroke sequence have been used and solved problems probably related to ESD, but there is no concrete evidence it is an internal discharge "hardware". The sequence to enter in the ESD screen is as follows:

switch the calculator to ON;
press and hold [ON] key;
press and hold [D] key;
release [ON];
release [D];

The calculator enters in interactive test mode. Now press [MTH] key and the display shows:

ESD 210V 210V
     ||   ||
The calculator will beep for a while; see if there is any warning message. To get rid of the test screen, do it:
press and hold [ON] key;
press and hold [C] key;
release [ON];
release [C];

Now try the calculator again. If the problem is related to ESD, it is probably solved.

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