CASIO fx-3600P scientific calculator from 1985

[jebem]

This specimen remained for almost a year for sell at a local auction site.
Finally I decided to acquired it, for the principesca amount of 15 Euro.

It was made in Japan after 1985, according to the Hitachi HD43147 SoC processor date code.

Casio fx-3600P calculator forensics: arcsin(arccos(arctan(tan(cos(sin(9)))))) = 9.0000157179
Tested in DEG mode.
Typed: 9 sin cos tan INV tan INV cos INV sin
Result1: 9.000015718
Typed: - 9 =
Result2: 1.57179 -05
Typed: x 1000000 =
Result3: 15.7179

Note the "Lithium" label printed at the bottom left side of the display bezel.
I believe it relates to the case silver color, although the CR2025 power cell also contains Lithium.




Front panel was kind of lose, due to the adhesive film dried glue.




As usual with CASIO machines, opening the case is extremely easy.
The back cover is fixed with four screws that, once removed, allows the cover to slide and lift.

It uses a single 3 Volt CR2025 Lithium battery cell.
The power consumption is 0.430 mW (average current of 0.14 mA)




Two classic axial pass through mount 1/8 Watt 5% resistors on the PCB back side.
Top = 390 Ohm, Bottom = 220KOhm




PCB front side.
Keyboard assembly (foil membrane attached to the PCB).



One unmarked SMD ceramic capacitor at top left side.
And the Hitachi HD43147 SoC processor, made in 1985 week 43 (5J 43).




Keyboard rubber membrane.



Real quality plastic keys, sporting injection molding manufacturing.
These keys don't "click" to give a mechanical feedback, but they register successfully on every single key stroke after so many years of usage.
And when they fail to register, a easy cleaning is all it takes to restore normal operation.




Partial exploded view.