hp-91 transistor substitution
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09-20-2014, 07:17 PM
(This post was last modified: 09-20-2014 07:50 PM by jebem.)
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RE: hp-91 transistor substitution
(09-20-2014 05:10 PM)joseaem Wrote: Hi all. Hola, The 3 transistors are from Motorola (the "M" indicates the manufacturer, and the 3 digits are the manufacturing date). So the references are: "3-393" --> this probably is a PNP transistor "3-374" --> this probably is a PNP transistor "4-071" --> this probably is a NPN transistor Edited to add this: My cross reference comes from this information here. (just for reference, Motorola identification code is "185") You are lucky because the transistors cases have the Emiter (E), Collector (C) and Base (B) pins well indicated, so that is a good starting point: it means they are bipolar silicon NPN and/or PNP semiconductors. Take a digital multimeter set to measure Volts, put the negative probe to the Emiter pin and the positive probe to the Collector of each transistor. If you are lucky, a voltage will be there during the normal operation of the calculator. If the reading is positive, the transistor should be a NPN type. If the reading is negative, the transistor should be a PNP type. I would use fast switching high gain transistor for both NPN and PNP positions, capable of about 0,5 to 1 Amp of current, working with at least 50 Volt Vcb, and a minimum of 0,5 Watt of dissipation power. There are thousands of possible replacements that will work on that position. For example: NPN: PN2222A NPN: PN2907 One final note: You may like to acquire the Manuals on CD/DVD from this MoHPC. They have lots of manuals including Service Manuals as well (the HP-97 is included and it is close enough for this task). Jose Mesquita RadioMuseum.org member |
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Messages In This Thread |
hp-91 transistor substitution - joseaem - 09-20-2014, 05:10 PM
RE: hp-91 transistor substitution - jebem - 09-20-2014 07:17 PM
RE: hp-91 transistor substitution - joseaem - 09-21-2014, 04:10 PM
RE: hp-91 transistor substitution - Paul Berger (Canada) - 09-20-2014, 10:20 PM
RE: hp-91 transistor substitution - joseaem - 09-21-2014, 05:12 PM
RE: hp-91 transistor substitution - cruff - 09-21-2014, 11:32 PM
RE: hp-91 transistor substitution - Paul Berger (Canada) - 09-22-2014, 01:55 AM
RE: hp-91 transistor substitution - joseaem - 09-22-2014, 06:36 PM
RE: hp-91 transistor substitution - jebem - 09-22-2014, 07:51 PM
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