Path: csiph.com!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail From: Piotr Piatek Newsgroups: sci.electronics.components Subject: Mysterious part in an old calculator Date: Sun, 17 Apr 2016 17:17:16 +0200 Lines: 14 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: individual.net 0umWrtf8ABTfgqPgftsMbwBkCDkX9cIIHnjl0ahY+aHiJLnD0t Cancel-Lock: sha1:V28yZCEkfsBWUT6hFclqRFv0GpU= User-Agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/20130330 Thunderbird/17.0.5 Xref: csiph.com sci.electronics.components:5964 Could someone identify the blue part (marked on the board SC81EIA4R7M), please? http://www.pisi.com.pl/piotr433/misc/bluething.jpg It's used in an old calculator Casio FX-602P, manufactured in year 1984. The part is connected across the power supply pins of the static RAM chip uPD444G. It could be a capacitor (but other capacitors on the board look ordinary and are marked differently), or perhaps a varistor or a Zener diode. Here's the FX-602P circuit diagram drawn by me: http://www.pisi.com.pl/piotr433/fx602sch.pdf and a photo of the whole board: http://mycalcdb.free.fr/galerie/Casio/casio_FX-602P.4.jpg