Elektronika MK 60 calculator: my summer gift from Russia

[jebem]

Time to dismantling the machine.
This just requires to remove two screws on the back cover.
And another six to release the PCA and display/solar panel.





There is a white ink hand written label with a unknown number: 808039.
The serial number in the back cover is also 6 digits, but it is different: 847948



The SoC is a Russian КБ145ВХ3-2 made in 1988 week 08.
The 20µF/6.3V paper electrolytic capacitor was made in 1988 week 06.

This SoC operates from 1.5Volt nominal (with a minimum of 1.2V and a maximum of 1.8V), supplied by a 4 element solar panel, and consumes around 25µA.
This SoC contains 10,000 transistors to support a 5405 bits ROM microcode, RAM registers, ALU, keyboard scan, display decoding and control, synchronization unit and power supply.

I measured the solar panel under strong warm light (60 Watt at 40cm distance) and got 1.42Volt.
All four elements generates about the same voltage of 0.355 Volt.
This is a little lower than expected but it happens that the capacitor is dry and has resistance leaking, so it is pulling down the power supply a little.

A uncommon design choice by today's standard was to use two АЛ102Г yellow LED diodes to protect the SoC from over-voltage.

The schema can be downloaded from here.