The battery in the timekeeping circuit MK48T02B of my MV/3200 is flat

The power supply now runs fine and the MV/3200 starts every time but with a tweak; since the battery in the timekeeping circuit MK48T02B-12 is flat, every power on test stops at the character “D”. Since the MK48T02B, in addition to being an ultra low power SRAM and a real-time clock, it also is the power-fail control circuit which fails on power up. In order to power up, power must be applied, the date and time set and then leave the system on for a few minutes. Rapidly power off and then on makes the power on tests pass.

I have ordered and received a new MK48T02B-12 but I am waiting for a de-soldering gun that I have ordered to arrive before replacing the chip.


  1. #1 by Michael Laajanen on Saturday 6 April, 2013 - 14:09

    Pity I did not find you site in time since I have a few brand new Timekeeper chips.

    Anyhow, if you need help in replacing it let me know I do HW design for a living :)

    Remember when I read “the soul of a new machine” so I really would love to visit you place some time .


    Michael Laajanen

    • #2 by Tommie on Saturday 6 April, 2013 - 17:21

      Thanks for the offer. Much appreciated! :-) I bought an MK48T02B from Elfa and a desoldering gun from China since desoldering tools runs at about SEK 4000 and up SEK11000! Well beyond what I can afford. The desoldering gun is a great tool but mine came with a tip that is to big. The inner hole diameter is 1,5mm is way too big. Luckily, after contacting Hakko, their Swedish rep called me and since they are phasing out their desoldering gun, they offered to sell me desolderding nozzles they used to charge SEK 200 for, for SEK 50 so I purchased 4 nozzles, the smallest one having an inner diameter of 0,8mm that should work. We’ll see. I should have them on Monday.

      Since I only have the one circuit board I am very vary of using a soldering iron a hand operated solder sucking pump since it is very easy to apply too much heat and thus wrecking the board traces. If the desoldring gun fails (I will test on a scrapped PC NIC), I will leave the MK48T02B in the board and cut the pins as close to the plastic casing as possible after which I will remove one pin at the time using a pair of pliers pulling at the circuit side and applying heat at the other side of the board. Another solution is to cut across the MK48T02B between pins 12 and 13 down to the lower section of the MK48T02B and cut open the MK48T02B at the end where the battery is. This way I can remove the top “cover” from the chip and replace the dead battery.

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