Early
Electronic
Calculator		 Hewlett-Packard 21 Calculator

Manufacturer: Hewlett-Packard
Model: 21
Year: 1976
Form: Pocket
Functions: RPN Scientific
Number of Digits: 12
Display Type: LED
Display:Hewlett-Packard 1990-0495
Logic Technology: LSI-2
Diodes: 7
Transistors: 2
IC Complement:Hewlett-Packard / AMI 1820-1741
Hewlett-Packard / AMI 1820-1382 J
MOSTEK MK60025N 1818-0129
Batteries: 2 AA NiCd
Power Connector:10 VAC, 2-pin special
Tech. Data Level: 2
Tech. Data Source: RE
Tech. Data Pages: 1
Tech. Data:Schematic (pdf)

Notes:

- Unit Log -

Serial Number: 1607S20660
Year of Manufacture: 1976 (ICs and caps stamped with 7605,7614)
Date of Receipt: 1976
Source: Purchased new.
State upon Receipt: Brand new.
Current State: Fully functional (12 Jun 2000).

Date: 1997 Jul 17
Procedure: Batteries replaced with power supply module. Some internal rewiring performed to accomplish this.

Date: 2000 Jun
Symptoms: 1 and 4 keys intermittent
Analysis: Battery gas had caused corrosion.
Procedure: Attempt at cleaning through the PCB hole for the keys. Improved.

Date: 2000 Jun
Procedure: Power supply modifications undone and 2 batteries installed.

Date: 2004 Jan 17
Procedure: Battery substitute inserted.


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