Elektronika MK-52, MK-61

Serial number	MK-61: 91 12 608446, made in Russia, around 1991
Accessories	Pouch
	Manual (Russian), 208 pages, originally written on a typewriter, undated
	220V AC power supply, operational
	Big sheet of paper showing a schematic of the internal curcuit together with repair notes (Russian)
	Original cardboard box (Russian), dated 12/1991
Condition	Excellent. There is a piece of tape attached on top of the display.
Repairs, Comments
Acquired	2.2.2003

Serial number	MK-61: 90 02 291787
Accessories	None
Condition	Good.
Repairs, Comments
Acquired	22.9.2004

Serial number	MK-52: 90 10 181752
Accessories	Plastic cover
	Manual, Part I (Russian, pages 1-183)
	Manual, Part II (Russian, pages 186-383)
	Original cardboard box (Russian)
	Big sheet of paper showing a schematic of the internal curcuit together with repair notes (Russian)
Condition	Excellent!
Repairs, Comments
Acquired	22.9.2004

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Type, Precision, Input mode	Scientific, 8 BCD digits, exponent ±99, Reverse Polish Notation
Programmable	Yes, keystrokes, 105 program steps, no editing except overwrite.
Performance Index	0.40 This is by far the slowest machine in my collection! The already pretty slow HP-55 (1975) is 2.5 times faster. The HP-15C which was introduced about one year earlier (1982) is almost 7 times as fast. The HP-71B which was introduced one year after the MK-61 (1984) is 53 times as fast.
Memory	15 storage registers (0-9, a-e), 105 program steps. MK-52: Nonvolatile EEPROM memory for program and data - but the data must explicitly be copied to EEPROM! MK-61: Volatile memory.
Display	8 digit mantissa, 2 digit exponent, separate signs, green LED. The display is extremely dim and the green numbers are hard to read behind the green display cover.
Special features	RPN entry mode, regular 4-level stack, T-register is not changed upon stack drop.
Original Pricing, Production	MK-52: 1981 (115 rubles) - around 1991 MK-61: 1983 (85 rubles) - around 1992 Made by Elektronika in Russia. The back label indicates that these units were made in the KWASAR factory.
Batteries	4xAA or external AC power supply (MK-52) 3xAA or external AC power supply (MK-61)
Dimensions	Length 16.8cm, Width 7.7cm, Height 3.5cm
Links	MK-61 Command Reference. MOSCOW: MK-52, MK-61 (Andrew Davie) Soviet Calculators Collection: MK-52, MK-61 (Sergei Frolov) RSkey: MK-52, MK-61. Key map, Pseudo-writing mode, Journey Of Big Numbers (Gregory Escov)
Comment	Definitely a cool device! Provides a powerful set of programming functions. One of the most advanced Soviet calculators ever made. Mechanically, the unit is of very cheap making. The keys provide no feedback whatsoever and the display is so dim that it is hard to read. Apparently, the MK-52 and MK-61 are pretty much the same units. However, the MK-52 is equipped with two card slots for expansion ROM packs.

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