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Elektronika MK-52: The MK-61 big brother?
10-27-2014, 05:51 PM
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Elektronika MK-52: The MK-61 big brother?
While the Elektronika MK-61 and MK-52 presents a common set of features, the MK-52 adds constant memory and external IO ports.

Usually constant memory is implemented using static RAM with a power backup mechanism.
Not in the MK-52: It uses a writable ROM to allow users to save their programs on demand.

I got this MK-52 at a fair price, and despite the seller claiming for a good working condition, this is not the case.
Also the case was opened, as the back screw seal is missing.
So this will be one of my next restore projects.

It powers ON, but the display flickers, then shows all the dots like the batteries were depleted (using fresh alkaline AA batteries).
However I managed to do some math operations and it did OK on that, meaning that at least the logic circuits are in good shape.

Somehow I was expecting this behavior. These machines are old (vintage) and were stored for many years in a shelf, usually in harsh environmental conditions.
Electrolytic capacitors in the DC-DC converter power supply are usually the first components to fail under these conditions, specially when reapplying energy on them.
These caps where made in 1984, while the calculator was made in 1986.
I had no time and the mood to start diagnosing the calculator, but my guess is that these caps are dry and have lost the capacitance long ago.

Surprisingly, the internals looks to be in the original condition (untouched solder joints and components).
The keyboard foam, used to keep the hard plastic keys in place without rocking too much, is sticky and needs a urgent replacement, though.

So, I need to check and fix the power supply first, then I will see if it can write to the KP1601PP1 EEPROM as well.

First set of pictures:

[Image: mk52_001.jpg] [Image: mk52_002.jpg] [Image: mk52_003.jpg]

[Image: mk52_004.jpg] [Image: mk52_006.jpg] [Image: mk52_007.jpg]

[Image: mk52_008.jpg] [Image: mk52_010.jpg] [Image: mk52_011.jpg]

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Elektronika MK-52: The MK-61 big brother? - jebem - 10-27-2014 05:51 PM

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