Elektronika MK-61 dead digit :(

[Druzyek]

In 2003, I added an Elektronika MK-61 to my collection and used it occasionally for useful things for a few years before it went into a box for the next ten years. When I put batteries in it today, I noticed that the first digit and minus sign no longer work:
   
I took it apart and saw some gunk on the back near the side of the screen that stopped working:
   
There are no capacitors anywhere near there that could have leaked. One time, a board I made worked fine for a few months before malfunctioning, and the culprit turned out to be left over flux. That board worked again after I scraped the flux off, so I tried to carefully carve through the gunk between the traces on the MK-61 but it didn't help.

The only other thing I noticed is the white blob on the lower left of the display in the picture above. It covers two of the five wires leading into the display, as well as some of the traces. Of course, I would be very, very hesitant to start scraping at it, but I did notice that none of the other pictures I have found show anything similar:




Maybe they made minor changes to the manufacturing process over time or it's a repair that happened to a defective display before it was put in the calculator or something.

Any ideas how I can get it running again?

[Kees van der Sanden]

Hi Druzyek,

The connection between the metal pins and the glass is very fragile.
Perhaps there was a bad contact at test and they glued it this way.
Replacing the display is the best way forward.

Replacement displays are still sold on Ebay.
Search for: display MK61 or display ILC2
I ordered a few some time ago. Due to poor packaging 2 out of 5
had some broken pins on arrival. I contacted the seller and he sent me
some new displays well packaged.

Best regards,

Kees

[Benjer]

The MK-61 that I have has a similar white blob on the front and still functions normally, so perhaps it's supposed to be there.

[Druzyek]

Quote:Replacing the display is the best way forward.

Replacement displays are still sold on Ebay.
Search for: display MK61 or display ILC2

I just happen to have one I picked up for a $1 or less on one of my travels. I'll give it a try.

Quote:The MK-61 that I have has a similar white blob on the front and still functions normally, so perhaps it's supposed to be there.

That makes sense

Anyone have an idea of how to remove the screen and the blob without damaging the traces the blob dripped onto?

[Hlib]

(08-05-2018 03:55 AM)Druzyek Wrote:  ...I noticed that the first digit and minus sign no longer work...

This defect is common here. The problem is not the VFD, but the output key chip. It is cheaper to replace the calculator than to repair it.

[Druzyek]

Quote:The problem is not the VFD, but the output key chip.

Ok, I'll save my replacement display then. Is there a way to be sure that that chip is malfunctioning without changing the display?

[Hlib]

(08-13-2018 09:25 PM)Druzyek Wrote:  ...Is there a way to be sure that that chip is malfunctioning without changing the display?

Cut off the faulty segment and try to signal it from a working circuit to make sure finally.

[Druzyek]

(08-15-2018 01:13 PM)Hlib Wrote:  

(08-13-2018 09:25 PM)Druzyek Wrote:  ...Is there a way to be sure that that chip is malfunctioning without changing the display?

Cut off the faulty segment and try to signal it from a working circuit to make sure finally.

Do you have a pinout or datasheet for it? I know it is old. I would like to know how to drive it myself if I don't use this extra display in the calculator. I can use a datasheet in Russian or English.

[Hlib]

So, You can PM about details of purchasing or repairing due to this calc.