Elektronika MK-61 - today I ordered one NIB

[x34]

(09-18-2014 07:04 PM)aurelio Wrote:  [sure I'll ask somebody if are available or where may i find this kind of vintage calculators; sure not in the vintage and souvenirs touristic markets...

I know, should be easier a check on TAS, but you agree that walking for local shops it's more exciting

Actually, Elektronikas MK-51/54/52 and B3-21/34 could be spotted at Moscow Vernissage Izmaylovo touristic/flea market, but B3-19 and MK-152/161 are unlikely to be seen there.

However, it is much easier and cheaper to obtain them from Russian online auction avito.ru

[jebem]

I just returned from Portuguese Customs to collect my MK-61 calculator.
It arrived to Portugal in 3-Sept, and as usual the Customs took almost 3 weeks to send me the notification letter to go there and pay the import duties.

I have to say that the calculator looks like it has been used extensibility, or at least it has been stored in poor conditions.
I was expecting it to be in better shape, for something sold "as New".

Anyway, when arriving home at the end of the day I will report here if it works...

Edit:
Yes, it is working fine.
The keyboard key's action is worse than seen on Casio calculators, but at least it never fails to register.

[jebem]

(09-19-2014 08:29 PM)Francois Lanciault Wrote:  I bought a MK-52 a few month ago. It works for about 2 days then died.

I am now a bit reluctant to order an other one...

François

Did you check the usual suspects, like battery contacts and power switch?
Also check the keyboard as the keys can easily cause issues.

[Francois Lanciault]

(09-23-2014 11:46 PM)jebem Wrote:  

(09-19-2014 08:29 PM)Francois Lanciault Wrote:  I bought a MK-52 a few month ago. It works for about 2 days then died.

I am now a bit reluctant to order an other one...

François

Did you check the usual suspects, like battery contacts and power switch?
Also check the keyboard as the keys can easily cause issues.

Yes I did, I opened the calculator and check with a voltmeter that the current was reaching the PCB. I also tried with a regulated power supply. For the power switch I tried by-passing it again directly on the PCB.

Did not even had time to try to enter a first program...

F.

[jebem]

Today I had a chance to have a more detailed look on this calculator.
It is new, despite missing the display plastic sticker protection.

This was a good deal, considering the asking price.

And it is the only calculator that I know of showing the official price engraved in the back during the manufacturing process!
85 Rubles was the asking price in 1996, July. Calculators for the people!

Concerning the current consumption:
I measured 95mA with fresh IKEA Alkaline batteries, with just a single Zero digit and the decimal point light after Power on.
This is within the specifications given in the back cover (4.5V and 0.6W).

Following are some photos, where the small case defects are exaggeratedly displayed, as a result of strong sunlight and modern digital camera machines:







Great VFD display: much easier to read than those LCD displays of the same era (90's):





The original 1996 warranty factory seal, over the fixing screw on the back cover:
Never opened! Well, not yet...





Label translation:
MicroCalculator "Elektronika MK 61"
Manufactured: 96 07 Serial Number: 777868
U.n=4.5V P.n=0.6 W
Price 85 Ruble

[jebem]

The supplied external power adapter model "Elektronika D2-10m".

Specifications:
Input 220V 50Hz
Output 5V 0.1A
Manufacturing date: 93 03

The power regulation is good enough for this application (readings taken with input at 231 VAC):
- Voltage on open circuit: 8.6 V
- Voltage with 47 ohm resistive load: 5.2 V (111 mA)
- Voltage with 33 ohm resistive load: 4.9 V (146 mA)

[jebem]

(09-25-2014 02:47 PM)Francois Lanciault Wrote:  Yes I did, I opened the calculator and check with a voltmeter that the current was reaching the PCB. I also tried with a regulated power supply. For the power switch I tried by-passing it again directly on the PCB.
F.

Hi Francois,
Sorry to know about that issue on your MK-52 machine.

Probably the next step is to check the internal DC-DC converter power supply operation.
If the calculator VFD doesn't light up, probably the 27V line is faulty?

I think it is a good idea to use a oscilloscope to check the DC-DC oscillator section (you can borrow one from a friend or from a school, if you do not have one with you).
The DC-DC oscillator converter is a simple circuit with a few silicon transistors; one of them can be faulty; also check the electrolytic capacitors, one of them can be faulty as well.



EDIT:
Additional information on the DC-DC converter internal power supply

Both calculator models (Mk-52 and MK-61) takes the battery supply to generate a number of Negative output supply voltages for the electronics.
The battery Positive terminal is used as Ground as well.

MK-52 DC-DC power supply:

Common:
+BATT/GND (pin9) -> Gnd/+5V to IC's like EEPROM KP1601PP1 Ucc2 pin 24.

Input:
-V1 -BATT (pin7)

Output:
-V2 -15V (pin6) -> IC logic circuits
-V3 -27V (pin5) -> to the VFD display
-V4 -17V (pin8) -> to the -12V regulator for Ucc1 pin 12 and Gnd pin 4 of EEPROM KP1601PP1
-V5 -40V (pin4) -> to the -33V regulator for programming voltage Upr pin 15 of EEPROM KP1601PP1
~V6: 2.4VAC (pin 1 and 3) -> to the VFD display filament [Edit]

Note on the EEPROM:
KP1601PP1 == ER2401 (1024x4 bit)


MK-61 DC-DC power supply:

Common:
+BATT/GND (pin9) -> Gnd/+5V to IC's

Input:
-V1 -BATT (pin3)

Output:
-V2 -15V (pin4) -> IC logic circuits
-V3 -27V (pin7) -> To the VFD display
~V4: 2.4VAC (pin 1 and 2) -> to the VFD display filament [Edit]


The following attachment diagram shows the MK-52 four output voltage DC-DC converter power supply.

[Francois Lanciault]

Thank you Jebem,

I will have a look at this tonight and will probably come back to you with some questions!

François

(09-26-2014 09:52 AM)jebem Wrote:  

(09-25-2014 02:47 PM)Francois Lanciault Wrote:  Yes I did, I opened the calculator and check with a voltmeter that the current was reaching the PCB. I also tried with a regulated power supply. For the power switch I tried by-passing it again directly on the PCB.
F.

Hi Francois,
Sorry to know about that issue on your MK-52 machine.

Probably the next step is to check the internal DC-DC converter power supply operation.
If the calculator VFD doesn't light up, probably the 27V line is faulty?

I think it is a good idea to use a oscilloscope to check the DC-DC oscillator section (you can borrow one from a friend or from a school, if you do not have one with you).
The DC-DC oscillator converter is a simple circuit with a few silicon transistors; one of them can be faulty; also check the electrolytic capacitors, one of them can be faulty as well.



EDIT:
Additional information on the DC-DC converter internal power supply

Both calculator models (Mk-52 and MK-61) takes the battery supply to generate a number of Negative output supply voltages for the electronics.
The battery Positive terminal is used as Ground as well.

MK-52 DC-DC power supply:

Common:
+BATT/GND (pin9) -> Gnd/+5V to IC's like EEPROM KP1601PP1 Ucc2 pin 24.

Input:
-V1 -BATT (pin7)

Output:
-V2 -15V (pin6) -> IC logic circuits
-V3 -27V (pin5) -> to the VFD display
-V4 -17V (pin8) -> to the -12V regulator for Ucc1 pin 12 and Gnd pin 4 of EEPROM KP1601PP1
-V5 -40V (pin4) -> to the -33V regulator for programming voltage Upr pin 15 of EEPROM KP1601PP1

Note on the EEPROM:
KP1601PP1 == ER2401 (1024x4 bit)


MK-61 DC-DC power supply:

Common:
+BATT/GND (pin9) -> Gnd/+5V to IC's

Input:
-V1 -BATT (pin3)

Output:
-V2 -15V (pin4) -> IC logic circuits
-V3 -27V (pin7) -> To the VFD display


The following attachment diagram shows the MK-52 four output voltage DC-DC converter power supply.

[jebem]

The Elektronika MK-61 Operations Manual includes the schematic in A3 paper format.
It was a nice feature from the old CCCP/USSR manufacturing plants, allowing the owners to peek around and do their own repairs if they wanted to.

From the schematics, we can identify the following main components.

IC's:
D1: К745ИК1302-2 (K745IK1302-2) - Control Unit for Processor, Display and Keyboard;
D2: К745ИК1303-2 (K745IK1303-2) - Arithmetic Processor;
D3: К745ИР2-2 (K745IR2-2) - Memory Registers;
D4: К745ИР2-2 (K745IR2-2) - Memory Registers;
D5: К745ГФ3-2 (K745GF3-2) - Clock Generator.
D6: К745ИК1306-2 (K745IK1306-2) - Additional MK-61 Processor features not present on the B3-34 series;

The VFD:
VL1: ИЛЦ2-12/8Л (ILC2-12/8L or ILZ2-12/8) - Vacuum Fluorescent Display. Filament voltage: 2.15 - 2.9 V. Filament current: 20 - 24mA. Brightness: 700 cd/m^2. Number of sign: 12 (including 8+2 digit sign). Size of the sign: 2.4 x 4.3 mm. Color: Green. Lifetime: more than 10000 hours.

The Transistors:
VT1: кт361г (KT361G) - PNP Si 250MHz, hfe>50, 35V, 0.05A, 0.15W
VT2: кт315б (KT315B) - NPN Si 250MHz, hfe>50, 20V, 0.1A, 0.15W (schematics diagram wrongly present it as PNP);
VT3: кт814г (KT814G) - PNP Si 3MHz, hfe>60, 50V, 3A, 10W
VT5: кт315б (KT315G) - NPN Si 250MHz, hfe>50, 35V, 0.1A, 0.15W

The printed schematics was scanned at 300dpi in grey, and cropped in 6 overlapping parts to maintain the resolution after the upload.

[Benoit Maag]

There are a few apps on ios and android that can help understand the inner workings of the MK-61

The english version on ios is not an exact replica of the original (added/modified functions) and the help section is not very clear - so half helpful. There was also a Russian version on ios (ipad only) but it looks like it is no longer on the app store.

Namir also checked the android store and apparently there is an exact replica in english of the original, so this may help as well to understand the working of the machine

I got one a few weeks ago from Ukraine. Works OK but it is very slow and there seems to be no PAUSE function to show intermediate results.

[jebem]

(09-28-2014 03:27 AM)Benoit Maag Wrote:  I got one a few weeks ago from Ukraine. Works OK but it is very slow and there seems to be no PAUSE function to show intermediate results.

Hi Benoit,
Yap, it is slow, but it has some followers around because of its pelicularities.

I'm still in process of understanding what the calc can do.
Because I couldn't find a non Russian version of the operation guide, I'm translating it to English.
I have scanned the original printed guide and then used ABBY fine reader for OCR processing.
And now I'm using my spare time to translate it. The OCR capture doc has lots of errors which forces me to type in the correct Russian words before doing the translation.

To pause a program peraphs the 5th key on the 1th row - that is the equivalent R/S key from the HP machines.

[jebem]

I'm in the process of translating the Russian instruction guide.
To help me, I'm using information collected with the help of other contributors that have posted in this thread with useful links.

I have started this task by creating a diagram with the Latin transcription of the original Russian Cyrillic calculator keyboard.
And for that I have used the HP-67 as a inspiration model.

(Latin keyboard image was updated on 29-Sept)

[d b]

(09-28-2014 03:27 AM)Benoit Maag Wrote:  ...............I got one a few weeks ago from Ukraine. Works OK but it is very slow and there seems to be no PAUSE function to show intermediate results.

Ben; Jose or others might be interested in a photo of yours. I myself have never seen one with a blue screen and that towering rad/grad/deg toggle is just weird. If I'd have bought it new, the first thing I'd have done is to take a toe nail clipper to that thing - or put aircraft warning lights on it.

-----------------------

Jose; I'll be downloading or buying a copy of that if I may.

[jebem]

(09-28-2014 05:12 PM)Den Belillo (Martinez Ca.) Wrote:  (...) that towering rad/grad/deg toggle is just weird. If I'd have bought it new, the first thing I'd have done is to take a toe nail clipper to that thing - or put aircraft warning lights on it.
-----------------------
Jose; I'll be downloading or buying a copy of that if I may.

Hi Den,

Those Russians guys enjoy their angles in the 3 once popular units...
I took the sin(x) for x=45 Degrees, then for x=50 Grads, and at last for x=Pi/4 Radians, and the results were exactly the same: "7.0710681-01".
Storing the results in 3 registers and subtracting each two of them gives always Zero as the answer.

As for the English User Guide, it will be available as totally freeware inside our community, of course.
But I'm in the beginning of the work; at the moment I am dealing with the Russian technical expressions found in the original user guide against what I can find as appropriate in English calculator "vocabulary".

[Benoit Maag]

These are the pictures of the MK-61 I bought recently.
Indeed, the display cover is blueish and the angle unit selection switch is unusual (and very high).
[attachment=1092][attachment=1094][attachment=1095]

For reference, see the lot# information in the back - I do not know how to interpret it
[attachment=1093]

Looking forward to the translated manual - Thank you Jose for working on this

I bought the machine from this vendor - the pictures he shows are of a machine similar to the one I bought: http://cgi.ebay.com/ws/eBayISAPI.dll?Vie...1606786671


Benoit

[jebem]

(09-28-2014 09:44 PM)Benoit Maag Wrote:  These are the pictures of the MK-61 I bought recently.
Indeed, the display cover is blueish and the angle unit selection switch is unusual (and very high).

For reference, see the lot# information in the back - I do not know how to interpret it

Looking forward to the translated manual - Thank you Jose for working on this

Benoit

Hi, Benoit,
Nice machine, in blue display!
Your machine manufacturing date as 1994, January. Probably one of the last batches ever made?

Label translation:
MicroCalculator "Elektronika MK 61"
Manufactured: 94 01 Serial Number: 271797
U.n=4.5V P.n=0.6W
Price 85 Ruble

The angle unit selection switch lever is indeed very long, and I have seen it in black or white color in the seller's adverts.

[jebem]

Concerning the MK-61 Russian User Guide contents, is anyone aware of this MK-61 operation requirement, referred in the initial Chapter 1 - "Notice to Owners", point 1.8.:

"After turning off the MK, allow a minimum of 30 seconds before switching it on gain."

Whatever the reason for such recommendation, I'm following it by the letter, just in case... I wonder if some sudden deaths reported for this calculator are related to this small detail.

EDIT:

In addition to the above, there are two more remarks concerning the operation safety rules:
1. "Plugging the external power supply adapter to the 220V outlet power while the calculator is not connected to the adapter, is prohibited".
2. "The use of rechargeable batteries is prohibited".

[jebem]

I manage to complete the translation to English of the Russian Elektronika MK-61 user guide.

This is a draft version, so it is possible to find one or another mistake in the text.
Despite the big work involved, I had a lot of fun in this task, as I managed to learn a bit about how these Russian machines behaves.

The ZIP file is available here to download.

You do not need a premium account to download it, but it will delay the download a bit in the low speed free access.

There is a lock in the file, but of course it is easy to open it once you say:
I_like_RPN_gadgets!

[rprosperi]

(10-08-2014 12:25 AM)jebem Wrote:  I manage to complete the translation to English of the Russian Elektronika MK-61 user guide.

Ok, now you've done it! I had been able to convince myself I don't want (need) one of these Russian RPN machines since I can't understand the manual, and can't even read the keyboard. Damn.

Nice job on the manual Jose! At least, I think it's a nice job... in any case, it took a LOT of work and looks quite nice, thanks for that and for sharing.

[Massimo Gnerucci]

Thanks a lot Jose!