Электроника C3-22 – an ordinary calculator with an extraordinary integrated circuit

In the early 1970s, engineers from the Leningrad Electronic Instrumentation Association “Svetlana” (Светлана) began work on the next calculator, the Электроника C3-07 (Elektronika C3-07). This device was a rather simple design with only fifteen keys, meaning that some functions had to be assigned to the same button. Such a solution was quite problematic, more than once there were mistakes, and also just typing in the right sequence took quite a long time. In the successor to the C3-07, the designers had to eliminate these inconveniences.

Calculator Электроника C3-22

A successor with the designation C3-22 (Электроника C3-22) appeared in 1976. The calculator was similar to its predecessor, but the case was much larger. With more keys, the problem was solved – two functions assigned to one button. The device supported addition, subtraction, multiplication, division, calculation of percentages, operations on constants, and changing the sign of a number. The case was made of plastic, which could come in a variety of colors. The display is actually a single VFD separated by a pane of translucent green plastic, in my copy it is unfortunately cracked. The keyboard is quite clumsy, and the keys themselves have a large stroke, on the plus side we can credit the fact that the keys were made by injection molding of two shades of plastic, so that the key markings have survived to this day. The calculator, like other devices from the 1970s, is powered by mains voltage, unfortunately the cable cannot be detached as in the Elwro 144, it is an integral part of the device. It is also worth mentioning that in 1987 this calculator was renamed from Электроника C3-22 to Электроника MK22. However, this was only a name change, functionally it was still the same device.

On the underside of the device you will find nothing but a few screws and a rather large plate informing us that this is an electronic microcalculator made in the USSR. In addition, the production date of the first month or quarter of 1985 and the serial number were found here.

WOGN Gold Medal (https://elektronika.su/all/elektronika-s3-22/)

It is interesting to note that the Электроника C3-22 calculator won a gold medal at the Moscow VDNKh (All-Russian Exhibition Centers) in 1977.

As many colors, as many versions

Электроника C3-22 version 09 (https://sprzedajemy.pl/kalkulator-elektronika-c3-22-zsrr-parczew-2-0010c9-nr62662478)

As I mentioned earlier, the Электроника C3-22 calculator could come in many color variants. However, it is important to know that along with the color of the case, the interior could also differ, more precisely I am referring here to the integrated circuits used and the display lamp.

The calculator came in 11 versions – version 01 (beige/white), version 02 (cyan/blue), version 03 (gray/brown), version 04 (gray), version 05 (gray/red), version 06 (orange/black), version 07 (orange/white), version 08 (red/gray), version 09 (red), version 10 (white/blue), version 11 (white).

In the photo above you can see a copy in red (version 09), while my calculator is version 11 made entirely of white plastic.

What does the inside hide?

Interior of Электроника C3-22

After removing a few screws, you can remove the top of the case and look inside the device. Immediately you can see that all of the free space is occupied by a printed circuit, or actually two, since the transformer has been placed on a separate board. The motherboard itself is slightly tilted forward. The main printed circuit is quite modest, here you can find the keyboard which is an integral part of it, the main processor in a fancy case, the display which is a single VFD, and individual electronic components in the power section.

Transformer

A separate PCB houses the mains transformer, which has quite a number of taps (+0.7V, -24V, -27V, +3.15V, -30V). Thanks to a separate board, the mains voltage is separated from the rest of the device. An on/off switch for starting the calculator has also been placed right next to the transformer.

Power section

At the top of the motherboard is a power section consisting of eight semiconductor diodes devoid of any markings, as well as resistors and capacitors that form RC filters to smooth out the voltage.

Display Электроника C3-22

The calculator’s display is a single VFD lamp capable of displaying thirteen digits, but twelve are used. The lamp’s leads were placed on both sides, and there were plastic pieces holding it in place. In my copy, the lamp has, on the left side, a circle symbol and a vertical and horizontal line, but these are not used.

Электроника C3-22 interior of one of the earlier versions (http://www.leningrad.su/museum/show_big.php?n=1661)

In earlier versions of the calculator, you can find another lamp devoid of symbols on the left side and having, as many as fourteen digits. If we are already at the early versions of this calculator, we can move on to the most interesting issue, namely the main processor.

According to most sources describing this calculator, the device was based on three integrated circuits. K145IKK6 – arithmetic-logic unit (circular case with leads on each side), K145GG1 – clock pulse generator (circular element in the upper left corner) and K145IP8 – input/output chip (rectangular case, gold-plated leads). You can see these chips in the photo above.

Main processor version 11

However, later versions of the Электроника C3-22 calculator such as mine were based on a completely different chip, designated K145BX1. In fact, this chip combined the functions of all three previously described chips. It must be admitted that this IC was placed in a really fancy casing. It was made of glass and metal, and the cover itself with the designation was soldered on. Interestingly, this type of housing was used exclusively at the Leningrad Svetlana factory. The chip has, as many as 48 leads, which are made of aluminum. This chip was used, also in other Soviet calculators.

Unfortunately, as in the case of other Russian chips, we can’t find any documentation here. It must suffice for us that the K145BX1 chip is a full-fledged chip that can be used in a calculator, without the need for other peripheral chips. As a curiosity, I can mention that according to the “Information book on the content of precious metals in products and components of general industrial use. Approved by the First Secretary of the CPSU in 1985 and the Ministry of Defense of the USSR in 1986.” The K145BX1 chip has exactly 0.0028 grams of gold inside it.

Bottom of the motherboard

We can also look at the underside of the motherboard. It is devoid of any electronic components, we can only see here the paths connecting the components from which the calculator was built.

Device in operation

Sources:

  • http://www.leningrad.su/museum/surf.php?cat=10
  • http://www.leningrad.su/museum/show_big.php?n=1661
  • https://ru.wikipedia.org/wiki/%D0%AD%D0%BB%D0%B5%D0%BA%D1%82%D1%80%D0%BE%D0%BD%D0%B8%D0%BA%D0%B0_C3-22
  • https://www.cpu-world.com/forum/viewtopic.php?p=204987

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