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Old 28th Jun 2011, 10:41 am   #2
Kat Manton
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Join Date: Jul 2005
Location: West Yorkshire, UK.
Posts: 1,700
Default Re: Mostek/ST 'Timekeeper' IC (Sun NVRAM) repair

Part II

This is what was left of the poor thing after Part I.

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Next, I carefully removed the encapsulation from around the pins at either end, keyed the top of the device with fine abrasive paper and cleaned it with IPA.

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Pin 1 can still be easily identified on the device itself.

M48T02 (24-pin DIP)
  • The pins adjacent to pins 1 and 24 are for the crystal.
  • The pin adjacent to pin 12 (VSS) is cell -ve
  • The pin adjacent to pin 13 is cell +ve

M48T08/18 (28-pin DIP)
  • The pins adjacent to pins 1 and 28 are for the crystal.
  • The pin adjacent to pin 14 (VSS) is cell -ve
  • The pin adjacent to pin 15 is cell +ve

In both cases, the cell -ve pin is adjacent to and connected to the VSS pin; the cell +ve pin is on the same side as the VCC pin.

Next, I stuck copper foil strips on top of the device (after making the small holes) and applied Evo-Stik contact adhesive. I made the -ve connection the longer of the two.

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I then keyed and cleaned the underside of the coin cell holder, applied Evo-Stik then carefully stuck the holder in position, making sure the polarity was correct.

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Finally, I soldered all the connections and soldered on a watch crystal.

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As a finishing touch, hot-melt glue could be applied over the soldered connections and used to secure the crystal.

All that remains to be done is to shove it back inside the computer, fit the cell and load the MAC address, host ID etc. back in.

Kat
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