Re: *Unused* HP-21 apparently dead - Please help! Message #6 Posted by Alain Jacques on 5 Mar 2004, 6:18 a.m., in response to message #2 by David Smith
Hello Jorge,
I assume you have followed David's pertinent advices ... it is a pity if it has not cured the problem. The 21 is quite sensitive to polarity inversion, so please be cautious about rebuilding a battery pack. If the calculator has been turned on recently, the problem is probably not an aging capacitor. The 21 innards are made of 3 boards (keyboard, logic and LED display) interconnected by rows of pins. It may be a bad contact. It is rather easy to cleanly open the calculator by removing the battery pack and the four screws underneath the rubber feet; the top of the shell will then open, the remaining plastic clamp on the bottom will offer some more resistance. Be cautious not to bend the pins and not to fry the electronics with a static discharge.
Regards,
Alain
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