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    It has been a while since I changed an RTC module on a vintage motherboard so when one came in for repairs here, I thought it a good chance to take some pictures and do some pages documenting it for those who are interested.  

     This board was sent to me recently by a vintage PC collector in Southern California. His early Pentium board is a fine example of the clone boards available in the mid to later 1990s, and like many the Real Time Clock module was not holding its settings due to the age of the battery that is internal to the RTC module.  

  These were typically 24 pin Dallas Semiconductor DS1287 or DS12887 RTC modules soldered in and present a bit of work to remove on the typical 3 or 4 layer motherboards of the time.  Removing a older style battery with two pins is fairly easy for most people with some soldering experience as you can heat up one lead, and then pull it free, then heat the other and pull it free.   As you can imagine it becomes difficult when you have more than two pins, and trying to get all 24 pins on an RTC up to 700 plus degrees and pulling them all at once is a trick if you don't have one of those large specialized soldering rigs with a tip that fits the 24 pins at once and lots of heat.

   Those of us who can't spend the big bucks for a special tip and monster soldering rig just to remove one size chip, will use normal pin by pin desoldering techniques where you use a vacuum desoldering iron, or a standard iron and some desoldering wick.  I fortunately many years ago got the chance to buy a good used PACE digital soldering station that has vaccuum or pressure air flow, and controls two irons with full digital temperature control so that you take less chance of damaging a board by over heating it. 

    After the first pass with the vacuum desoldering iron, the RTC mounting site looks like this below - most of the pins are desoldered and free moving but two still are partially stuck.

 

The trick here is to get the pin fully heated and then add a bit of new solder to help loosen up the old, then hit the vacuum button to pull the melted solder out. Then I rock the lead with the tip of the soldering iron a bit back and forth to be sure its free.  Then go on to the next pin - or if you are worried about overheating skip to a pin on the other side, going back and forth so one side does not get too much heat in the same zone in a period of time.

SafeSurf

DMC Firewall is developed by Dean Marshall Consultancy Ltd