Did you quickly spot which key is missing? Elektronika MK-61
Boosty - https://boosty.to/icher
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Let's look at the device itself.
Let's start with the price.
It's on the back cover.
MK-61 - 85 rubles
And here's the price range for the mid-80s, just so you know how much it was.
Average salary in the country - 190 rubles
Ice cream - 10 kopecks
Doctor's sausage, 1 kg - 2.20 rubles
Cassette recorder - 190 rubles
The calculator ran on three AA batteries or a 5-volt power supply.
By the way, look at that interesting connector – proprietary, yes, that's what they'd call it now, wouldn't you?
There are two small slide switches on the case.
One turns on the power.
The second selects whether the calculator will calculate angles in radians, grads, or degrees.
The numbers are very pleasing to the eye.
This isn't an LCD—it's a vacuum fluorescent display.
Inside is a small glass vacuum tube with electrodes, almost like a miniature radio tube.
When voltage was applied to them, the phosphor began to glow—that's why the numbers were so soft, green, almost cosmic.
By the way, the instructions said to turn it on again only after 30 seconds.
The problem is that charge remains in the power circuits for some time: in the capacitors, in the indicator circuit, in the logic.
If you turn it back on immediately, the calculator might not start from a clean state: it might freeze, display chaotic characters, or behave strangely.
I confirm, I checked this.
Three colored keys are striking:
yellow F opens the second layer. Commands
For example, a regular keystroke is +, and pressing F on the same key enters the number pi
The blue K key opens another layer of commands—the blue labels on the keyboard
So, the keyboard here is like a three-tiered one: a regular command, a command with F, and a command with K
And the red CX key clears the contents of the X register
Now take a closer look: what key is missing here?
Hint: this is the most important key on a regular calculator
Three seconds to answer
Three
Two
One
There's no equals key
And here a natural question arises: how the hell do you calculate then?
This also stumped me at first.
I couldn't even calculate 2 + 2 the first time.
I typed two, plus, two—and that's it.
And then what?
And here begins one of the most interesting themes, in my opinion, in the history of calculators.
#retrotechnology #shorts