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Elektronika MK-52: The MK-61 big brother?
05-08-2020, 09:07 AM
Post: #61
RE: Elektronika MK-52: The MK-61 big brother?
The display pin next to the 'VL1' text looks like it hasn't been soldered to its pad.

— Ian Abbott
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05-10-2020, 04:11 PM (This post was last modified: 05-10-2020 04:13 PM by Daniel..)
Post: #62
RE: Elektronika MK-52: The MK-61 big brother?
Hi there.

I took advantage of this gloomy afternoon to unclog the metallic holes.

A varnish has been passed over the integrated circuits and hinders cleaning.

What product to use to remove it around the metallic holes ? Acetone ?

Thank you.

[Image: 09.jpg]
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05-10-2020, 07:43 PM
Post: #63
RE: Elektronika MK-52: The MK-61 big brother?
(05-08-2020 08:47 AM)Daniel. Wrote:  Hi there, yes, the glass envelope of the display is broken.

You might be able to repair this. I'm assuming it might be too hard to fuse a new glass evacuation tube to the existing module without damaging it beyond repair, but possibly some vacuum compatible epoxy might suffice if you have access to a vacuum pump. I don't know offhand what sort of vacuum is required for a VFD to operate.
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05-11-2020, 05:50 AM (This post was last modified: 05-12-2020 05:13 AM by jebem.)
Post: #64
RE: Elektronika MK-52: The MK-61 big brother?
The VFD display is available as a spare part from Ukraine, the country where those calculators were made during USSR era and after that a few years more.

eBay lists several sellers, some offering them at around one to three USD each plus s&H. I bought some of those a couple of years ago and paid around four USD for shipping.
Look for "ILC2-12/8L VFD Display Nixie Tube for Calculators Electronika MK-52 MK-61" and you will find several offering.

The keyboard will not have any positive action when pressing the keys, no matter what kind of foam I used. This seems to be a characteristic feature of these MK machines.

To clean the PCB as well the enclosure parts I use warm water and dish detergent, and a soft brush.
Let it dry for 24 hours, preferably close to a window where it can get some mild heat, but avoid to expose the plastics of the enclosure to direct sun.

After that the PCB receives a proper cleaning with IPA applied with a soft brush.
I never use IPA on the cover, as the labels may be erased.

I never use acetone or other aggressive chemical reagents on electronics like these, so I can't comment on that.

Edit:
For IPA, see https://en.m.wikipedia.org/wiki/Isopropyl_alcohol
It is easy to find it in plastic bottles, 1000ml or 2000ml, in hardware stores.

Jose Mesquita
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05-12-2020, 12:31 PM
Post: #65
RE: Elektronika MK-52: The MK-61 big brother?
[Image: 10.jpg]

New condensers just arrived, immediately soldered. :-)

Still waiting for the VFD.

Regards.
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06-13-2020, 07:57 PM
Post: #66
RE: Elektronika MK-52: The MK-61 big brother?
Hi there, I'm looking for the schematics of the expansion ROM.

Regards
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06-28-2020, 02:29 PM (This post was last modified: 06-28-2020 04:13 PM by Daniel..)
Post: #67
RE: Elektronika MK-52: The MK-61 big brother?
Finally the VFD is arrived :

[Image: 12.jpg]

[Image: 13.jpg]

I put in place on the PCB and set the height over the PCB at about 2mm :

[Image: 14.jpg]

[Image: 15.jpg]

After soldered the legs I turn on the calculator, no magic smoke but display doesn't work properly with many dots and/or comma ...

[Image: 16.jpg]

Fortunately it was only a short circuit due to a small piece of solder which shorted two legs of the display. :-)

[Image: 17.jpg]

[Image: 18.jpg]
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06-28-2020, 06:31 PM
Post: #68
RE: Elektronika MK-52: The MK-61 big brother?
Nice photos for a successful repair, Daniel.
Thank you for sharing your work here.
Cheers,
Jose

Jose Mesquita
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07-01-2020, 01:15 PM
Post: #69
RE: Elektronika MK-52: The MK-61 big brother?
Hi, thank you Jose.

Regards
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