Elektronika MK-61 operation?

[james summers]

I'm awaiting the arrival of an MK-61 and have been working though Jose Mesquita's excellent English translation of the manual (many thanks for your hard work in producing this, Jose) and have noted the warnings about the order of connecting / disconnecting the power adapter, the need to wait 30 seconds after switching the calculator off before turning it on again, and the fact that rechargeable batteries should not be used.

Are there any other things I should look out for or be careful about in using the MK-61?

Many thanks

James

[bhtooefr]

I'm not convinced that there's a prohibition on rechargeable batteries at all.

Page 7, on PDF page 5 of the original Russian manual says the following:

Quote:во избежание разрушения элементов питания:
1) соблюдайте полярностъ включения;
2) запремается проводитъ подзарядку.

Translated using Google Translate:

Quote:3.3. To avoid damage to the batteries:
1) observe polarity of inclusion;
2) it is forbidden to recharge.

I'm pretty sure that what that's saying is, it's forbidden to recharge the A316 batteries (which I'd guess are zinc-carbon cells?). And, the damage would be to the batteries, not the calculator.

I've got Maha PowerEx 2700 mAh cells in my MK-61 right now...

[nsg]

(03-26-2017 03:01 PM)bhtooefr Wrote:  

Quote:3.3. To avoid damage to the batteries:
2) it is forbidden to recharge.

I think I have an idea where this came from. The power supply has a switch (З-Р, charge-operation) which supplies higher voltage in "charge" position and allows to charge Ni-Cd batteries in Б3-34. MK-61 uses same power supply. If you use A316 (which are primary cells and cannot be charged) this may damage the cells (and maybe cause fire), so what this note means is "even if your power supply has a "charge" selector, do not use it or you will damage the batteries".

In theory you may be able to put AA-sized Ni-Cd batteris and use "charge" to charge them while working, but in practice I am not aware of such batteries. NiCads of Б3-34 were completely different form factor.

[bhtooefr]

NiCd AAs are absolutely a thing, but I'm not sure I'd charge them using a relatively dumb power brick... (And, I just checked, my Д2-37 power brick has a hole for the З/Р switch, but there's no switch in there.)

[james summers]

nhtooefr, nsg,

Thanks for the information, it will certainly help that I can use rechargeables. Makes sense about the charging/charger, thinking about it I thought it had to be something like that rather than the slightly lower voltage from rechargeables.

Still waiting for my MK-61 to arrive, tracking information showed it arrived in the UK at the Heathrow Distribution centre on Thursday night but no update since then.

[Eddie W. Shore]

FYI: There is an MK-61 emulator for the iOS (iPhone/iPad/iPod Touch):

https://itunes.apple.com/us/app/mk61+-pr...43067?mt=8

It's only $0.99. I have not seen an Android version (yet).

[bhtooefr]

There's two free ones on the Play Store:

MK 61/54: https://play.google.com/store/apps/detai...om.cax.pmk
Extended emulator of MK 61/54 (a fork of the previous one): https://play.google.com/store/apps/detai...ax.pmk.ext

There's also a package to donate $0.99 to the developer of the second one: https://play.google.com/store/apps/detai...pmk_donate

[james summers]

Thanks Eddie, I'll look into that for the iPad.

Fortunately, my MK-61 has now arrived. I thought the decimal point key was a bit iffy but eventually realised that if I want to enter a number between 0 and 1 I need to enter 0 first and then the point, I can't just press the point and then the digits after it as it only recognises the point if it comes after a digit (including 0).

Trying Richard Nelson's 5, ENTER, CHS, 2, + test from his HP RPN Evolves article in HP Solve #27 shows that the MK-61 follows case 2 of Classical RPN returning 7, similar to most of the Classics and Woodstocks.

The exploration continues.....

Edit: corrected "...Richard Nelson's 7, ENTER, CHS, 2, + test..." to "...Richard Nelson's 5, ENTER, CHS, 2, + test..." - thanks for the spot, Joe.

[james summers]

Thanks bhtooefr, will see if I can get hold of an Android device, my wife's has an iPhone and I've got an Ubuntu Touch phone, not much hope of an emulator for that!

[toml_12953]

My 61 has a very dim display, even when I use it with the AC adapter (plugged into a transformer to allow use in the USA). Does anyone else have that problem?

Tom L

[Craig Bladow]

While the display of my MK-61 is not "bright" I also wouldn't call it "dim". I've only run it on batteries.

[toml_12953]

(04-01-2017 03:07 AM)Craig Bladow Wrote:  While the display of my MK-61 is not "bright" I also wouldn't call it "dim". I've only run it on batteries.

Mine must be defective, then. You'd definitely call this one's display dim!

Tom L

[nsg]

(04-01-2017 10:26 PM)toml_12953 Wrote:  Mine must be defective, then. You'd definitely call this one's display dim!

Defective is too strong of a word. It is probably just old. Tubes may have lost some vacuum, solder crumbled here and there, cathode step up circuit lost its oomph, that kind of things. Quality was never a strong suit of that model; if it works at all after all those years, it is a minor miracle.

[james summers]

I would agree with Craig, whilst the display is not bright I wouldn't go as far as to say dim, although I think using it in sunshine would be difficult. It's difficult to really show in a picture but here's my MK-61 with a Spice and Woodstock. (Edit > The MK-61 still has the protective tape over the display that it came with out of the box.)

[toml_12953]

(04-02-2017 12:38 PM)james summers Wrote:  I would agree with Craig, whilst the display is not bright I wouldn't go as far as to say dim, although I think using it in sunshine would be difficult. It's difficult to really show in a picture but here's my MK-61 with a Spice and Woodstock. (Edit > The MK-61 still has the protective tape over the display that it came with out of the box.)

If mine still had the tape over the display, you wouldn't be able to see it at all!

Tom L

[james summers]

Can't argue with that, that is dim!

[Cristian Arezzini]

Dim displays are a common "failure" on those calculators. Usually it's the electrolytic capacitors in the voltage regulator that are failing (that also caused problems with EEPROM use in the landscape model). I've fixed a few by replacing the capacitors, but you have to be careful since the boards are very cheap, and it's very easy to lift the traces...

[toml_12953]

(04-11-2017 08:17 AM)Cristian Arezzini Wrote:  Dim displays are a common "failure" on those calculators. Usually it's the electrolytic capacitors in the voltage regulator that are failing (that also caused problems with EEPROM use in the landscape model). I've fixed a few by replacing the capacitors, but you have to be careful since the boards are very cheap, and it's very easy to lift the traces...

Since I can't use the calculator as-is, I have little to lose by trying to replace the caps. What values(s) do I need?

TIA

Tom L

[Cristian Arezzini]

Tom, I myself found the info I another thread of this forum:
http://www.hpmuseum.org/forum/thread-2345.html
The values are also in the schematic that comes with the calculator. One particular calculator I fixed had a dim display AND a malfunctioning EEPROM. I checked the caps, and one of them was the wrong value and dated 1969. Obviously a previous "fix" using surplus components. Now the display is much better and the EEPROM works. After changing the caps, be sure to regulate the voltages using the trimmers, since the new caps could produce much higher voltages than needed...

[voltaage]

(04-01-2017 12:29 AM)toml_12953 Wrote:  My 61 has a very dim display, even when I use it with the AC adapter (plugged into a transformer to allow use in the USA). Does anyone else have that problem?

Tom L

You could try out these steps if they fix yout problem. I replied my experience in another thread of this forum:

https://www.hpmuseum.org/forum/thread-20...#pid153926