The Elwro 105LN is one of the first office calculators to be produced at the Elwro Wroclaw plant. This device is a direct successor to the 105L model and, in fact, the first mass-produced one since the early 1970s. The design is very interesting both in terms of technical solutions, but also in terms of history, which is not so obvious.
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At first glance, the calculator resembles other designs from the communist period. The case was made of plastic in two colors, the distinguishing element here is the blue-colored buttons. Interestingly, the buttons were made by injection molding two plastics of different colors at the same time, so their markings are still visible today. In the working part of the calculator there is still a dial, used to change the number of displayed decimal digits, and a button to turn on the device, whose function is actually a bit different than just closing the electrical circuit.
When the button is pressed, the flap pops up and to our eyes appears a display consisting of twelve VFD lamps and a single red lamp in the upper left corner, which symbolizes the minus sign. As I mentioned before, the power button does not close the electrical circuit, but only releases the locking of the display flap. In this case, does the calculator work all the time when plugged in? No, a small limit switch has been placed inside, activated just by the rising display flap. If you close it, the limit switch disconnects the circuit and thus turns off the device.
The Elwro 105LN supports the four basic mathematical operations in arithmetic logic. This means that first a number is entered, and then its sign. Wanting to perform the 6-5 operation, one had to enter 6 (+) 5 (-). The calculator had no memory, but could display a fixed number of digits after the decimal point (0, 2, 3, 4), selectable, as I mentioned earlier, by a dial.
Let's take a look inside the device
After removing the back panel and unscrewing the two screws underneath, you can take the calculator apart and look inside.
The upper part of the case houses the keyboard, the display flap mechanism and the green aperture of the VFD lamps. The second part of the case houses the calculator’s motherboard. Both the power section and the logic section are placed on a single printed circuit board. The components on the main board are quite numerous. The brain of the calculator is the MK6010 chip from Mostek, above it we find five hybrid circuits that control the VFD tubes and, of course, the tubes themselves that make up the display. There are also some transistors, resistors and capacitors on the board.
The power supply section is quite extensive, but this is not surprising after all the calculator is powered by mains voltage. The power supply is based on a JS4/3/57G transformer manufactured by the UNITRA-ZATRA Radio Transformers Plant in Skierniewice. There is also a rectifier bridge and some voltage smoothing components on the board. Also visible on the right side is the aforementioned limit switch, activated by the display flap.
The operation of the calculator is based primarily on this single MK6010L chip. It is a fairly successful design introduced in October 1971 and used in many calculator models. The manufacturer of this chip is the Western company MOSTEK, founded by former employees of Texas Instruments. We must admit that the chip looks really interesting, the silicon enclosed in a black square is placed on a ceramic substrate, and the chip leads themselves are gold-plated.
Being on the topic of the brain of this device, one can mention a curiosity. At the first version of this material, I only mentioned the white raven CT5001 chip from Cal-Tex Semiconductor, mounted instead of the MK6010L chip. Interestingly, I have since managed to obtain such a design. Unfortunately, it is only a motherboard in addition incomplete. Parts of the power section are missing, as well as the VFD tubes, which you can see someone ineptly soldered out destroying the paths on the other side. The laminate itself was manufactured at the TORAL plant in Toruñ and, due to a different layout and different components, differs from the original in terms of pathways. Unfortunately, it is hard for me to say where this design came from. I can only suspect that it is the creative invention of Polish engineers who reworked the original device.
Also stop for a moment at the hybrid VFD lamp control chips. In my calculator, these are Polish-made chips with the designation GC-003 (I wonder if IV 73 stands for the fourth month/quarter of 1973). The components were most likely manufactured by one of Telpod’s two plants – OBREM (Center-Research and Development… I couldn’t find the full abbreviation, but the company was probably headquartered in Krakow) or OBRMHiR (Research and Development Center for Hybrid Microelectronics and Resistors). The display controller in the Elwro 105LN may also have been based on JRC IC-3552 chips, chips in black cuboid format.
The display, as I mentioned earlier, is made of twelve VFD tubes, which are held by a plastic guide. A lamp is also visible in the upper left corner, serving as a minus symbol.
The lamps themselves were also not manufactured in the factories of any communist country. It is of Japanese design with the designation DG10 and comes from the FUTABA plant. Interestingly, this company is still in operation and is currently manufacturing VFD, LCD and OLED displays.
On the motherboard next to the processor, you can also see transistors in rather fancy cases.
On the other side of the motherboard we find nothing but tracks. However, two things are interesting – firstly, the immediately visible inscription JAPAN, by which we can infer that the board comes from this country. Also noteworthy is the plastic connector for plugging in the keyboard. Its presence means that my calculator most likely comes from the early years of production. In later years, due to production costs, such a solution was abandoned and the wires were soldered directly to the PCB.
Who actually created the Elwro 105LN?
The processor is of Western manufacture, the tubes are Japanese, even the motherboard itself says JAPAN. I think quite a few of you are now asking yourselves – who actually designed this calculator? The only Polish touches in this design are the VFD lamp drivers manufactured at Telpod’s plant and the UNITRA-ZATRA transformer, but no wonder, after all, we have a different voltage standard in Japan.
The truth is that the Elwro 105LN in terms of design was not a Polish design. The calculator was based on the Japanese Exec 120-DN developed by Busicom. In the photo you can see the interior of this device, which is almost identical to the center of the Elwro 105LN.
In 1971-1975, he participated in preliminary talks in Poland and Japan, and then in negotiations with CHORI and BUSICOM, which led to the signing of a contract by ELWRO’s Foreign Trade Office for the purchase of “knowhow” for the production of electronic calculators that were very modern for the time, and which were put into large-scale production in their Polish version under the name ELWRO 105L. Compared to the calculators previously produced at ELWRO, this was a big leap in design and technology, which resulted primarily in the reliability of use. Mastering the production of this calculator, with the successive introduction of Polish components, allowed the company to gain new design and technological experience, which laid the groundwork for Elwro’s own development of subsequent calculators.
I think this excerpt, which is the memoirs of Mr. Andrzej Myszkier, M.Sc. fully explains where the Elwro 105LN calculator came from in Poland.
It must be admitted that the gradual introduction of Polish components into the Japanese calculator was indeed successful – own tube drivers, reworked power supply section, Polish-made passive components. Considering that the Elwro 105LN was the second calculator produced in Poland, the introduction of all these changes is quite a success.
So is the 105LN model a Polish design? And yes and no, because on the one hand the calculator was produced in Wroclaw’s Elwro plant, later even with Polish components, but its design originated in Japan and in fact the device was designed there.
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Sources:
- http://www.calcuseum.com/SCRAPBOOK/BITMAP/BONUS/16404/_SMD34869_XL.htm
- https://web.archive.org/web/20200213221445/http://computermuseum.informatik.uni-stuttgart.de/dev_en/bsicm_120/bsicm_det.html
- https://elwrowcy.pl/
- https://pl.wikipedia.org/wiki/Elwro_105LN
- https://www.tomaszgrebski.pl/blog/maszyny-liczace/pierwszy-polski-kalkulator-elwro-105-ln
- https://www.nac.gov.pl/