DS12887 pcb substitute with battery

allison ajp166 at verizon.net
Mon Jan 23 04:57:12 CST 2017

On 01/22/2017 02:46 PM, Chuck Guzis wrote:
> On 01/22/2017 10:57 AM, allison wrote:
>> I don't know about most people but this solution has been around for 
>> decades.
>> I locate the battery on the failed part with a small magnet, then
>> grind the epoxy down to it then pick it out with a sharp pointed
>> tool.  Once I expose the connection point I older two wires then
>> epoxy a small coin-cell holder in that spot and it s done.  I've done
>> this more times than I care to count and its effective and the
>> replacement battery some over 10 years old now have not failed.  But
>> just in case I have a bag of NOS replacements (and pulls from
>> socketed boards) all with dead batteries from age.  There is no magic
>> to this.
> It's worth noting that the original post was about fabricating a
> replacement using the DS12885A RTC chip.  However, most old PCs used the
> DS1285 RTC (inside of a DS1287  module).  The DS12885A is supposed to be
> drop-in compatible with the DS1285, but apparently, in some cases is not.
> So there's logic in reworking the old DS1287 modules, as the DS1285 chip
> is long out of production--you'll most likely have to be content with
> pulls or the occasional NOS lot.
> --Chuck

I haven't seen that version for a while.  The later are fully versions
are epoxy filled.
Same for the MT48T part, same fix.

The problem with NOS parts is manufacture date.  Some are really old.


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