Elektronika MK-52: The MK-61 big brother?

[Adalin]

So I finally got the eeproms, and started the procedure immediately



I cut the legs off





I accidentally sucked off two solder pads with my solder sucker, that was not a wise move but I didn't want to use a de-solder wire because I didn't want to heat up the pads too long, it really is a crappy pcb, extremely fragile.



I cleaned up the solder and soldered the new eeprom in place and fixed the broken pad with a piece of wire



I wrote a small program and saved it and turned off the calculator for a couple of minutes before I restarted it and loaded the program and executed it. It worked!



there we go, another one works as it should do.

I bought another mk-61 last week also, and it had a strange fault when I started it, the vfd would show every number and point lit and scramble all the numbers then turn off completely for a minute or so before the calculator jumped to life and worked, it looked like a capacitor problem so I opened it up and found one 50v 20µF capacitor in the power supply pcb, I changed it and the problem went away.

I put the capacitor in my esr meter and it showed 20 Ohm internal resistance and vloss of 30%. compared to the new one I put in that measured 0,13 Ohm.

So if you have problems with your mk-XX calculator, replace the capacitors first.